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Senior Theses
Student Publications
4-20-2017
The Effect of Caffeinated Energy Drinks on the
Inhibition of Prepotent Responses
Kristina Karapetyan
Lake Forest College, [email protected]
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Karapetyan, Kristina, "The Effect of Caffeinated Energy Drinks on the Inhibition of Prepotent Responses" (2017). Senior Theses.
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The Effect of Caffeinated Energy Drinks on the Inhibition of Prepotent
Responses
Abstract
One of the goals of my study was to investigate the validity of the inhibition model presented by Friedman and
Miyake (2004) who proposed three inhibition categories. My study examined how tasks from the Prepotent
Response Inhibition category correlate among each other and how they relate to attention, impulsivity and a
task from the different inhibition category. Additionally, my study tested how caffeinated energy drinks affect
inhibition and attention performance. Sixty-six individuals who were randomly assigned into decaffeinated
and caffeinated conditions completed a battery of inhibition, attention, and impulsivity tasks. My study didn’t
detect any significant associations among Prepotent Response Inhibition tasks. Although my study failed to
find significant impact of caffeinated energy drinks on inhibition, I found a significant effect of caffeine on
attention. More research is required to establish the validity of the model proposed by Friedman and Miyake
and to reveal underlying components of inhibition.
Document Type
Thesis
Distinguished Thesis
Yes
Degree Name
Bachelor of Arts (BA)
Department or Program
Psychology
First Advisor
Naomi Wentworth
Second Advisor
Sergio Guglielmi
Third Advisor
Karen Kirk
Subject Categories
Social Psychology
This thesis is available at Lake Forest College Publications: http://publications.lakeforest.edu/seniortheses/100
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Printed Name: Kristina Karapetyan
Thesis Title: The Effect of Caffeinated Energy Drinks on the Inhibition of Prepotent Responses
This thesis is available at Lake Forest College Publications: http://publications.lakeforest.edu/seniortheses/100
i
LAKE FOREST COLLEGE
Senior Thesis
The Effect of Caffeinated Energy Drinks on the Inhibition of Prepotent Responses
by
Kristina Karapetyan
April 20, 2017
The report of the investigation undertaken as a
Senior Thesis, to carry one course of credit in
the Department of Psychology
___________________________________
Michael T. Orr
Krebs Provost and Dean of the Faculty
______________________________
Naomi Wentworth, Chairperson
______________________________
Sergio Guglielmi
______________________________
Karen Kirk
i
Abstract
One of the goals of my study was to investigate the validity of the inhibition
model presented by Friedman and Miyake (2004) who proposed three inhibition
categories. My study examined how tasks from the Prepotent Response Inhibition
category correlate among each other and how they relate to attention, impulsivity and a
task from the different inhibition category. Additionally, my study tested how caffeinated
energy drinks affect inhibition and attention performance. Sixty-six individuals who were
randomly assigned into decaffeinated and caffeinated conditions completed a battery of
inhibition, attention, and impulsivity tasks. My study didn’t detect any significant
associations among Prepotent Response Inhibition tasks. Although my study failed to
find significant impact of caffeinated energy drinks on inhibition, I found a significant
effect of caffeine on attention. More research is required to establish the validity of the
model proposed by Friedman and Miyake and to reveal underlying components of
inhibition.
ii
Acknowledgments
I will forever be thankful to my thesis advisor, Professor Naomi Wentworth. I
would never have been able to finish my thesis without her guidance. Her support and
advice has been my motivation to complete this project. I am thankful for challenging me
and helping me to grow professionally.
I am grateful to Dr. Guglielmi and Dr. Kirk for their help and guidance
throughout this year. Also, I would like to thank Jeremy Berg, the member of Professor
Wentworth’s lab, for his assistance during the most challenging parts of my thesis.
Finally, I would like to thank my family members and friends who support me and have
faith in me.
iii
Table of Contents
Abstract……………………………………………….……………………………………i
Acknowledgements……………………………………………….…………………….…ii
1. Introduction……………………………………………….……………………………1
1.01. Inhibition……………………………………………….……………………2
1.02. Prepotent Response Inhibition………………………………………………5
1.03. Antisaccade Task……………………………………………………………8
1.04. Stop Signal Task……………………………………………………………13
1.05. Stroop Task…………………………………………………………………15
1.06. Resistance to Distractor Interference and Resistance to Proactive
Interference………………………………………………………………………18
1.07. Attention……………………………………………………………………21
1.08. Impulsivity…………………………………………………………………23
1.09. Caffeine Effect…….……………………………………………….………25
1.10. Present Study…………………………………………………………….…28
2. Methods……………………………………………….……………………………...29
3. Results……………………………………………….……………………………….35
4. Discussion……………………………………………….……………………….…..38
iv
5. References……………………………………………….……………………...……46
6. Footnotes……………………………………………………………………………..59
7. Tables and Figures………………………………………………………….….….….60
8. Appendix …………………………………………………………………………….66
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
1
The Effect of Caffeinated Energy Drinks on the Inhibition of Prepotent Responses
There are instances in our lives when we have to inhibit one action in order to
perform a different task. Whether you are driving a car and notice that a green light is
about to turn into red, or if you are studying for an exam and get distracted by a Facebook
message, there are two possible scenarios - to either execute or to inhibit your action.
The examples above demonstrate that the ability to inhibit actions may be very critical in
some situations. The concept of inhibition is often used in the psychological field as a
means of studying traits, as well as psychiatric disorders. For instance, studies have
examined inhibition in the context of aggression (Pawliczek et al., 2013), impulsivity
(Aichert et al., 2012), and personality (Vreeke & Muris, 2012). Similarly, multiple
studies have looked at the inhibitory abilities of people with such disorders as
schizophrenia (Beech, Powell, McWilliam, & Claridge, 1989), Attention DeficitHyperactivity Disorder (ADHD) (Nigg, 2001), and autism (Johnston, Madden, Bramham,
& Russell, 2010). Although the construct of inhibition is used extensively in
psychological research, there is no single, universally accepted definition of what
inhibition is and what are the valid ways to measure it. However, there are various
models of inhibition which attempt to explain and classify this construct and its
underlying components (Friedman & Miyake, 2004; Gorfein & MacLeod, 2007; Nigg,
2000).
My study aims to examine one of the most straightforward types of inhibition,
Prepotent Response Inhibition (PRI), the type of inhibition that is required when a person
suppresses an automatic response (e.g., suppressing a yawn during a conversation with
your boss). Also, I want to assess how Prepotent Response Inhibition correlates with a
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
2
purportedly different type of inhibition, Resistance to Distractor Interference, the type of
inhibition that is required when a person attempts to ignore external information that
interferes with an ongoing task (e.g., keep working on homework while your friend is
talking to you). Additionally, I want determine how Prepotent Response Inhibition relates
to the psychological constructs of attention and impulsivity. Finally, my study aims to
test how caffeinated energy drinks impact performance on the inhibition and attention
tasks.
My first goal is to investigate whether specific tasks thought to measure Prepotent
Response Inhibition correlate with each other; second, to show that performance on the
Prepotent Response Inhibition tasks correlate less well with a measure of Resistance to
Distractor Interference; third, to demonstrate that attention might be one of the
underlying components of the inhibition tasks; fourth, to investigate whether impulsive
people perform worse on the inhibition tasks compared to non-impulsive individuals; and
lastly, to test whether caffeinated energy drinks enhance performance on the inhibition
and attention tasks.
Inhibition
The field of psychology has certain constructs that are defined in an inconsistent
or unclear manner; one such construct is inhibition. As a result, many studies that assess
inhibition do not provide a clear explanation of the construct (Benedek, Franz, Heene, &
Neubauer, 2012; Cohen-Gilbert & Thomas, 2013). One of the reasons why studies above
poorly explain inhibition is because there is no single, widely accepted definition of
inhibition and there are various models that describe this construct in their own unique
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
3
way. For example, according to MacLeod there are two types of inhibition - cognitive
and neural where neural refers to inhibition on the neuronal level and cognitive refers to
inhibition of mental processes or representations (Gorfein & MacLeod, 2007). In
contrast, Rafal and Henik (1994) suggest that there are three types of inhibition:
inhibition of responding to signals at unattended locations (e.g., ignoring irrelevant
stimuli), endogenous inhibition of reflexes (e.g., suppressing automatic responses), and
reflexive inhibition of the detection of subsequent signals (e.g., detection of stimuli at the
attended locations slows down). Another widely accepted model of inhibition was
proposed by Nigg (2000), who differentiated three types of inhibition - cognitionexecutive inhibition (e.g., intentional suppression of motor behaviors), automatic
inhibition of attention, and motivational inhibition (e.g., anxiety-provoked inhibition of
responses in the context of rewarding or punishing circumstances). Although each of
these models offers some specific categories of inhibition, it is challenging to obtain
enough empirical evidence to support each inhibition category, as well as test how
inhibition categories correlate among each other. Friedman and Miyake (2004) described
three major reasons why it is challenging to provide a straightforward definition of
inhibition.
According to Friedman and Miyake (2004) one of the problems related to
defining inhibition is a task impurity problem, which means that we can never measure
inhibition alone since it always has to be the inhibition of some other process, for
example, an action or a thought. Therefore, when researchers are studying inhibition, they
automatically have to take into account the process that is being inhibited, which makes it
difficult to study the inhibition mechanisms alone. The second problem that Friedman
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
4
and Miyake identify is related to the tasks which are used to investigate inhibition. Many
of these tasks are employed due to the assumption that they involve inhibition without
empirically derived justifications that these tasks are in fact based on inhibitory
mechanisms (Friedman & Miyake, 2004). The last problem that Friedman and Miyake
describe is that the measures which are used to investigate inhibition often exhibit poor
reliability. This means that poor reliability puts an upper limit on the possible correlations
among the tasks, making it difficult to establish whether a low correlation among
inhibition categories is due to the different natures of these categories or because of the
poor reliability of the measures (Friedman & Miyake, 2004).
One of the models of inhibition that addresses all of the challenges described
above was proposed by Miyake and Friedman (2004). After analyzing previous studies
that investigated inhibition Friedman and Miyake proposed three inhibition categories:
1) Prepotent Response Inhibition is defined as the ability to “deliberately
suppress dominant, automatic, or prepotent responses” (p.104)
2) Resistance to Distractor Interference is defined as “the ability to resist or
resolve interference from information in the external environment that is
irrelevant to the task at hand” (p.104)
3) Resistance to Proactive Interference is defined as “the ability to resist
memory intrusions from information that was previously relevant to the task”
(p. 105)
One of the strengths of this model compared to other models is that it employed
the statistical technique of confirmatory factor analysis (CFA) in order to categorize
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
5
different types of inhibition. CFA was employed to understand how tasks, which are
traditionally used to measure certain types of inhibition, are associated with the type of
inhibition they purportedly measure. For example, Friedman and Miyake examined how
tasks that are often used to assess the inhibition of automatic responses, such as the
Antisaccade task1, the Stroop task2, and the Stop Signal task3, are associated with a
Prepotent Response Inhibition factor. The CFA analysis demonstrated that all of the tasks
mentioned above load most strongly on the Prepotent Response Inhibition factor
(Friedman & Miyake, 2004). By using the same statistical technique Friedman and
Miyake determined that the Prepotent Response Inhibition and Resistance to Distractor
Interference factors were closely related to each other; however, neither was related to
Resistance to Proactive Interference (Friedman & Miyake, 2004). These findings
demonstrate that inhibition should not be treated as a unidimensional concept. It is a
multidimensional construct, therefore while assessing inhibition, it is important to specify
which inhibition category is being examined.
Many of the current studies focus on investigating Prepotent Response Inhibition
because this inhibition type might have potential clinical and diagnostic implications
(Johnston et al., 2010; Noel et al., 2013). However, our understanding of Prepotent
Response Inhibition is still incomplete and my goal is to explore this construct and three
tasks that are commonly employed to measure it.
Prepotent Response Inhibition
As mentioned above, Prepotent Response Inhibition is defined in terms of the
active suppression of habitual responses. Some of the means that have traditionally been
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
6
used to measure Prepotent Response Inhibition include the Antisaccade task (Hallett,
1978), the Stop Signal task (Verbruggen & Logan, 2008) and the Stroop task (Stroop,
1935). One question I will address in my study is how valid the model proposed by
Miyake and Friedman is by investigating how the tasks that are used to measure
Prepotent Response Inhibition (the Antisaccade task, the Stop Signal task, and the Stroop
task) are related to one another.
One of the pieces of evidence that supports the argument that these three
inhibition tasks share a common mechanism comes from brain imaging studies. Some of
the studies demonstrated that similar brain structures, such as the dorsolateral prefrontal
cortex, exhibit higher than normal activation levels while individuals are performing
these tasks (Chevrier, Noseworthy, & Schachar, 2007; Everling, & Fischer, 1998;
Oldrati, Patricelli, Colombo, & Antonietti, 2016; Vendrell et al., 1995). Some of these
authors conclude that if the brain areas get activated while performing the inhibition tasks
then they must be involved in inhibition (Oldrati et al., 2016; Vendrell et al., 1995). Such
an argument might sound reasonable, however, one of the critiques of such a conclusion
is that the activation of a particular brain region during the performance of a task does not
necessarily mean that this region is directly involved in inhibition. The inhibition tasks
have a complex nature and they involve various components such as perception,
attention, working memory, etc. Therefore, a higher than normal activation in the dorsal
prefrontal cortex might indicate that one of underlying components of the inhibition
tasks, such as attention, is involved in the tasks. For example, it has been demonstrated
that the dorsolateral prefrontal cortex is critical for working memory functions (Curtis &
D'esposito, 2003). Therefore, one might speculate that the dorsolateral prefrontal cortex
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
7
is highly activated during the performance of the inhibition tasks not because the
inhibition mechanisms are active but because working memory is required to perform
such tasks. This demonstrates that because of the multidimensional nature of inhibition, it
is challenging to study inhibitory mechanisms by the means of brain imaging technology.
Assuming that Prepotent Response Inhibition tasks share similar cognitive
mechanisms, then the tasks should have relatively high correlations; however, conflicting
results have been found on this matter (Aichert et al., 2012; Clair-Thompson &
Gathercole, 2006; Howard, Johnson, & Pascual-Leone, 2014; Jacob et al., 2010; Livesey,
Keen, Rouse, & White, 2006; Shuster & Toplak, 2009; Ting, Schweizer, TopolovecVranic, & Cusimano, 2016). For example, Aichert and colleague (2012) tested the
relationship between the Antisaccade task, Stroop task, Stop Signal task, and a Go/no-go
task and determined that only the Antisaccade and Go/no-go tasks exhibited significant
correlation (Table 1). In contrast, Howard, Johnson, & Pascual-Leone (2014) found that
there was a significant correlation between the Antisaccade and the Stop Signal tasks.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
8
These inconsistencies might be a result of the problems associated with measuring
inhibition that were described above. Additionally, some of these studies might have had
low power meaning that they were not able to detect significant relationships among
tasks. Also, variations in how the tasks were implemented could have contributed to these
inconsistencies. Although all of these tasks might involve inhibition, they might employ
different inhibitory mechanisms. Therefore, the low correlations among these tasks can
indicate that these measures linked to separate inhibitory processes at the neural level.
However, another possible explanation of the conflicting results might come from the
fact that these tasks have poor reliability which put an upper limit on the possible
correlations (Friedman & Miyake, 2004).
One of the goals of my study is to attempt to settle the dispute between Friedman
& Miyake and the empirical work that has failed to support their findings and to test
whether there is a relationship between three tasks of Prepotent Response Inhibition –
Antisaccade task, Stop Signal task and Stroop task. In order to understand how these
tasks are used to measure inhibition, it is important to understand the nature of these tasks
which I will discuss in the next section of this paper.
Antisaccade Task
Antisaccade eye movements have been used widely in psychological and clinical
research. A broad range of psychological phenomena and mental disorders have been
studied in the context of the Antisaccade paradigm, including intelligence (Michel &
Anderson, 2009), schizophrenia (Fukushima et al., 1998), and depression (Carvalho et al.,
2014). Prepotent Response Inhibition is one of the constructs that has been assessed by
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
9
employing the Antisaccade task (Friedman & Miyake, 2004). However, the Antisaccade
task was originally introduced as a task to measure frontal lobe dysfunction in general
(Hallett, 1978) and some studies (e.g., Michel & Anderson, 2009; Taylor, 2016) have
employed the Antisaccade paradigm for other purposes without fully explaining what this
task entails.
The goal of the Antisaccade task is to generate an eye movement in the opposite
direction of a stimulus (Hallett, 1978). It might seem like a simple task, however, most
people find it very challenging. The antisaccade error rate for healthy individuals is
approximately 20% (Hutton & Ettinger, 2006). Even when participants make no errors
the reaction time for generating antisaccades is 100-150 ms greater compared to a
prosaccade reaction time (Crawford, Parker, Solis-Trapala, & Mayes, 2010). The
question that arises is what might explain such differences between prosaccades and
antisaccades. There are two prevalent theories that describe the possible underlying
mechanisms of the antisaccades. The classical theory described by Hallett and Adams
(1980) states that the prosaccades are reflexive responses to the stimulus and in order to
generate an antisaccade, the prosaccade must be initially inhibited. According to this
theory, antisaccade errors occur as a result of a failure to inhibit the reflexive prosaccades
(Hallett & Adams, 1980). In contrast, a parallel processing theory advocates the idea that
the antisaccade and prosaccade eye movements are programmed simultaneously and
depending on which eye movement is generated faster, the corresponding eye movement
will be generated (Massen, 2004). According to this theory, the antisaccade errors occur
as a result of a more prolonged antisaccade preparation time or a faster prosaccade
generation time (Masen, 2004).
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
10
There is some empirical support for both models. One of the pieces of evidence
that supports the parallel processing theory is corrective saccades that participants often
perform when they make an error (Mokler & Fischer, 1999). Approximately 50% of the
time when participants perform incorrect saccades instead of correct antisaccades they
instantly perform a quick corrective saccade even though many participants are not aware
they do it (Mokler & Fischer, 1999). Subjects correct their mistakes within the normal
reaction time of prosaccade eye movements, which might indicate that there is an overlap
in prosaccade and antisaccade programming (Crawford et al., 2010). Another piece of
evidence in support of the parallel process theory is found in Masen's study in which she
manipulated the frequency of prosaccade and antisaccade trials (Masen, 2004). The
results showed a correlation between the probability of an antisaccade trial and the
reaction time to make it - as the probability of the antisaccade trials increased the reaction
time became faster (Masen, 2004). In contrast, the reaction time for the prosaccade trials
was not affected by the probability of a prosaccade trial (Masen, 2004). According to
Masen, such a finding supports the parallel processing model since it demonstrates that
the expectation of an antisaccade trial leads to a faster generation of an antisaccade
response, which outruns the prosaccade initiation time. Although such speculation seems
reasonable, a similar explanation might be applied equally well to the classical theory.
For example, the expectation of an antisaccade trial might make a subject more prepared
to inhibit the prosaccades instantly and to generate an antisaccade. Therefore, such an
argument cannot be considered decisive evidence for either theory.
The classical model is also supported by several pieces of evidence. For example,
some of the neurologically based studies investigated electrophysiology in primates,
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
11
human event-related potentials, and fMRI evidence and determined that in order to
successfully complete the Antisaccade task, inhibition of saccade neurons in the frontal
eye field and superior colliculus is needed (Munoz & Everling, 2004). According to
Munoz and Everling, these neurophysiological studies provide some support for the
classical theory because they show that during the preparatory interval, when a subject is
waiting for the appearance of the stimulus, neural firing rates in the frontal eye field and
superior colliculus are suppressed during the antisaccade trials compared to the
prosaccade trials. Although researchers suggest that this is an evidence of inhibition, such
conclusion might be fallacious. Saccade neurons are directional which means that some
neurons control saccades to the right and some neurons control saccades to the left. If
there was an inhibition of eye movements in a certain direction (left or right) only some
neurons would be suppressed. For instance, if a subject had to make an eye movement to
the left then neurons which are responsible for the right eye movements would be
suppressed. However, Munoz and Everling (2004) found that all saccade neurons in the
frontal eye field and superior colliculus are suppressed. Since there is a suppression of all
saccade neurons and not a specific inhibition of a prepotent response to a particular
location one might speculate that there are no underlying inhibitory mechanisms in the
antisaccades. This means that the argument presented by Munoz & Everling (2004)
cannot be considered decisive evidence for the classical theory.
Additional behavioral evidence for the classical theory is the antisaccade effect
described by Abegg and colleagues’ study (Abegg, Sharma, & Barton, 2012). Their
results revealed that the latencies of prosaccades were longer if the previous trial was an
antisaccade trial than if it was a prosaccade trial. Abegg et al. speculated that this might
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
12
reflect the carryover effect of inhibition in the antisaccade trials. Although such
speculation sounds reasonable, it is not certain whether such effect is observed because
the antisaccades inhibit the prosaccades or because there is a process of the active
reconfiguration where a brain switches from one task to another (Barton, Greenzang,
Hefter, Edelman, & Manoach 2005). These studies demonstrate that there is an ongoing
debate about which of these theories best explains the underlying mechanism of
antisaccades.
Another construct that should be considered in the context of the Antisaccade task
is working memory because it may be one of the underlying components of antisaccade
production. One piece of evidence in support of the role of working memory in
antisaccade production comes from neuroimaging studies (Matsuda et al., 2004).
Matsuda and colleagues (2004) showed that the dorsal prefrontal cortex, which is
considered a significant working memory region, is activated when antisaccades are
made but not prosaccades. Additionally, another piece of evidence comes from
behavioral studies in which participants had to perform antisaccades while doing a task
where working memory was involved (e.g., Mitchell, Macrae, & Gilchrist, 2002). The
study showed that as a memory load increased the number of the antisaccade errors also
increased. Subsequent studies tried to answer the question of whether working memory
moderates or mediates antisaccade performance. According to Crawford and his
colleagues (2011), the antisaccade performance is not mediated by working memory. In
their study, subjects with high and low working memory performed the Antisaccade and
the Prosaccade tasks and they found that antisaccade errors were strongly predicted by
the prosaccade latency and not by differences in working memory. Thus, Crawford and
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
13
colleagues concluded that working memory does not mediate antisaccade performance.
In another study, Schaeffer and colleagues (2014) investigated whether there is any
association between prosaccade latency, antisaccade errors, and working memory.
Specifically, Schaeffer et al. (2014) looked at how individual differences in working
memory performance relate to antisaccade errors when prosaccade latency is similar for
people with high and low working memory. They determined that among individuals
with similar prosaccade latency, those with a higher working memory had a lower
antisaccade error rate, which suggests that working memory moderates the relationship
between prosaccade latency and antisaccade error rate. Future studies are required to
uncover the detailed mechanism of the Antisaccade task and how it interacts with
working memory.
Stop Signal Task
Similarly to the Antisaccade task, the Stop Signal paradigm is a widely used
method in cognitive psychology for investigating Prepotent Response Inhibition. The
goal of the Stop Signal task is to determine the amount of time needed to stop a response
that is already in progress (Verbruggen & Logan, 2009). During the Stop Signal
paradigm, participants have to respond during the “go” trials and inhibit their responding
when they are introduced to a stop signal. As was true for the Antisaccade Task, there are
different models that describe the mechanisms underlying the Stop Signal task and some
of the most frequently discussed ones are the independent horse-race model and the
interactive race model (Verbruggen & Logan, 2009).
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
14
According to the independent horse-race model, there are two competing
processes that occur during this task - the stop and the go processes (Logan & Cowan,
1984). If the go process is more potent than a stop process then a response will be
generated, but if the stop process overrides the go process then the response will be
inhibited. During stop trials, the interval between the beginning of a trial and onset of the
stop signal is called the stop signal delay (Verbruggen & Logan, 2008). If the stop signal
delay occurs early in the trial there is a higher probability that the response will be
inhibited but if the stop signal delay is too long the response will seldomly be inhibited.
One of the challenges of the Stop Signal task is its assessment. Its major measurement, a
stop-signal reaction time (SSRT), can’t be examined directly since the measured behavior
has a covert nature (Logan & Cowan, 1984). Although the SSRT cannot be assessed
directly it can be calculated by using mathematical and statistical formulas based on the
independent horse-race model (Verbruggen & Logan, 2009).
In contrast, the interactive race model assumes that the stop process consists of
two stages. The first stage is an afferent stage during which the stop signal is detected and
the second is the interactive stage during which the go response is inhibited (Boucher et
al., 2007). According to this model, if the stop unit inhibits a go response before it
reaches a threshold, the go process will be suppressed which would result in no response.
However, in the case when the stop unit fails to inhibit the go process before it reaches a
threshold, the go response will be executed (Verbruggen & Logan, 2009). Interestingly,
these two models are similar to models described in the Antisaccade paradigm where the
interactive model is similar to the classical model and the independent horse model is
similar to the parallel processing model.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
15
In order to better understand the Stop Signal task, it is important to examine this
task at the neural level. Several studies have attempted to examine the neural
underpinning of the Stop Signal task. These studies have found that there are several
areas of the brain that are highly activated during this task, for example the presupplementary motor area (Duann, Ide, Luo, & Li, 2009), the inferior frontal gyrus
(Aron, Robbins, & Poldrack, 2004; Chevrier et al., 2007), and the right prefrontal cortex
(Aron et al., 2004). Another study demonstrated that lesions in the dorsomedial striatum
and subthalamic nucleus resulted in increased SSRT indicating that these brain areas
contribute to the Stop Signal task performance (Eagle et al., 2007). By looking at the
results of these studies, we cannot conclude that these brain areas are directly responsible
for the inhibition because they might reflect the occurrence of one of the components of
inhibition or some other process such as attention or working memory. Similarly, to the
Antisaccade task, more research is required to establish the elaborate neural mechanisms
that occur during this task.
Stroop Task
While Friedman and Miyake placed the Antisaccade and the Stop Signal tasks
into the Prepotent Response Inhibition category without much discussion they noted that
the Stroop task is more controversial. This task might be placed into two categories Prepotent Response Inhibition and Resistance to Distractor Interference. In order to
understand to which category this task belongs, the nature of this task has to be carefully
examined. The main goal of the Stroop test is to investigate how word meaning interferes
with naming the color of ink in which a word is printed. The task assesses whether
participants are able to inhibit the tendency to respond to the meaning of the word rather
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16
than the ink color of the word. Response latency for the incongruent condition, where the
ink color of the words and the color meaning of words are different (e.g., the word
“RED” written in blue ink) is longer compared to the response latency for a neutral
condition where participants name an ink of a non-color word (MacLeod, 1991).
Response times for the incongruent condition are usually 25% greater than for the neutral
condition. The results of the Stroop task are consistent across many studies (MacLeod,
2015).
The question is what is the cause of such consistent results? The initial theory that
tried to address the mechanism behind the Stroop effect was the speed of processing
theory, which suggested that the Stroop effect occurs because the reading process is more
automatic, compared to the color naming process since we have more training in reading
(MacLeod, 2015). Although this idea was prevalent for a prolonged time period, some of
the pieces of evidence demonstrated that this theory might be misleading. For example,
Dunbar and MacLeod (1984) challenged this theory by changing some aspects of the
basic Stroop task. They rotated the words upside down and backward which was
supposed to decrease the ability to read the words and to slow down the reading time. If
the speed of processing theory is correct people should be able to name the ink of the
color words faster than they do in a regular Stroop task. Contrary to the expectations, the
researchers demonstrated that even when words were rotated the Stroop effect was still
evident and participants took much time to name the ink of the color words (Dunbar &
Macleod, 1984). They suggested that such a finding demonstrated that there might be an
alternative model to explain the Stroop effect. One of the critiques of this conclusion is
that some people might be able to read upside-down; therefore, they will get the meaning
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17
of the words even when they are rotated. However, most of the people exhibit the
impaired ability to read the inverted words (Larsen& Parlenvi, 1984). This means that
there should be a more sophisticated model that can explain the Stroop effect.
Another model that explains the possible mechanisms behind the Stroop Task was
proposed by Cohen and colleagues - the parallel processing model (Cohen, Dunbar, &
Mcclelland, 1990). According to this model, when a person looks at the word, this person
perceives two stimuli simultaneously, a color of the word and the word itself. Therefore,
two pathways get activated and depending on which pathway will be more potent and
will faster reach a threshold, a respective response will be generated. One of the pieces
of evidence that is considered to support this model is practice effect. It has been
previously demonstrated that performance on the Stroop task improves with practice
(Davidson, Zacks, & Williams, 2003). According to the parallel processing model, the
relevant response gets stronger with practice and that is why the Stroop performance
improves. Still, the practice effect might be interpreted to support the speed of processing
theory where practice helps to inhibit the automatic processes very efficiently and
instantly produce the relevant response.
In order to fully examine the Stroop task, it is important to understand it at the
neurobiological level. One of the studies that has looked at brain activity during the
Stroop task demonstrated that such brain areas as the dorsal anterior cingulate and the
dorsolateral frontal cortex become more activated in people who perform the Stroop task,
compared to people who do not (Potenza et al., 2003). However, as it was mentioned
previously the results of these brain-imaging studies could not be used in order to
conclude that these brain areas are directly responsible for inhibition.
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18
One of the central questions is whether the Stroop task might be considered a task
that measures Prepotent Response Inhibition since in the literature, researchers often refer
to the Stroop effect as Stroop interference. Although Friedman and Miyake state that the
Stroop task belongs to the Prepotent Response Inhibition category, they never provide
any evidence why it might not be considered a task of Resistance to Distractor
Interference. Presumably, if the goal of this task is to inhibit a prepotent response, which
is reading, and to generate a voluntary response, which is naming of the ink color, then
the Stroop task would be considered a Prepotent Response Inhibition task. However, if
the goal of the task is to ignore the orthography of the word and concentrate on the
naming of the ink color then such task would belong to the Resistance to Distractor
Interference. One of the goals of my study is to investigate the relationship between the
Stroop task and the other Prepotent Response Inhibition tasks. I will test, for example,
whether there is a correlation between the Stroop task and the Eriksen Flanker task,
which is considered to be a Resistance to Distractor Interference measurement (Friedman
& Miyake, 2004).
Resistance to Distractor Interference and Resistance to Proactive Interference
Although according to Friedman and Miyake (2004), inhibition and interference
functions fall under the construct of inhibition, they are not synonymous. While
inhibition implies an active suppression process, interference refers to worsening of one’s
performance due to external and internal distracting factors. As noted previously,
Friedman and Miyake (2004) proposed two interference-related functions - Resistance to
Distractor Interference and Resistance to Proactive Interference. The main difference
between these two functions is that during Resistance to Distractor Interference the
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19
interfering stimuli appear simultaneously with the target stimuli. In contrast, during
Resistance to Proactive Interference the interfering stimulus, which is initially relevant, is
presented first, but during subsequent trials, it loses its relevance and distracts
participants from the target stimuli (Friedman & Miyake, 2004). Similarly, to Prepotent
Response Inhibition, Friedman and Miyake (2004) examined previous studies to identify
tasks that are commonly used to measure each function.
Resistance to Distractor Interference has been associated with the following tasks:
1) Eriksen Flanker task: Participants have to respond to a target letter that is
surrounded by other distracting letters
2) Word naming: Participants have to name a color of a target word that is
presented either alone or with distractor words of another color.
3) Shape matching: Participants have to indicate whether one shape matches
another shape that is presented either alone or with a distractor shape.
Resistance to Proactive Interference has been associated with the following tasks:
1) Brown–Peterson task: Participants have to memorize a list of words that belong
to the same category and reproduce them after each subsequent trial
2) AB–AC–AD: First participants have to remember cue–target word pairs, and
then participants need to learn a new list that is made up of the new target words
but with the same cues.
3) Cued recall tasks: Participants have to watch several lists of words and recall
the word from the most recent list
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20
Although these categories differ in their definition, they share some common
underlying cognitive mechanisms. For example, all three inhibition-related functions
(Prepotent Response Inhibition, Resistance to Distractor Interference, and Resistance to
Proactive Interference) require executive control and working memory for performing the
tasks successfully (Kane & Engle 2000; Long & Prat, 2002; Mitchell et al., 2002; Stuss et
al., 1999). Although the inhibition related functions share similar mechanisms, some
studies have demonstrated that people who perform well on one type of inhibition do not
necessarily perform as well on another type of inhibition (Howard et al., 2014; Noel et
al., 2013). For example, the main goal of the study by Noël and colleagues (2013) was to
test whether there is a difference in performance among tasks related to Prepotent
Response Inhibition and tasks related to Resistance to Proactive Interference in sober and
alcohol-dependent individuals. The study found that alcohol-dependent individuals
exhibited impaired Prepotent Response Inhibition performance while Proactive
Interference Performance remained intact (Noel et al., 2013). A different study by
Howard and colleagues (2014) examined the correlations among the Resistance to
Proactive Interference, Prepotent Response Inhibition, and Resistance to Distractor
Interference tasks and found no significant correlations, except for the correlation
between the Stop Signal task and the Eriksen Flanker task. Although these findings might
suggest that inhibition-related functions are relatively independent from one another,
such a conclusion might be misleading. For example, Noel’s study had a relatively small
sample size, which means that his study had a low power. In contrast, Howard and
colleagues employed a limited number of tasks from Resistance to Proactive Interference
and Resistance to Distractor Interference categories and assumed that they would obtain
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21
the identical results if they used different tasks from the same inhibition categories. For
example, they used only the Flanker test to represent the Resistance to Distractor
Interference; however, the assumption that the Flanker task can alone represent the
Resistance to Distractor Interference is fallacious since the performance on the tasks from
the same inhibition category is not always consistent with one another. Therefore, the
question of how performance on the Prepotent Response Inhibition, Resistance to
Distractor Interference, and Resistance to Proactive Interference tasks relate to each other
still remains unclear. In order to learn more about their relationship, I will examine one of
the tasks associated with the Resistance to Distractor Interference category, the Erikson
Flanker task, and determine how it correlates with Prepotent Response Inhibition tasks.
Attention
Many researchers study inhibition by assuming that it is an independent concept;
nevertheless, it is closely related to other constructs such as attention (Cohen et al., 1990).
For a long time it was thought that automatic processes do not require attention; however,
there are some pieces of evidence that suggest that attention is still important during
automatic responding (Cohen et al., 1990). In particular, attention is critical during
inhibition of automatic responses. According to Macleod & Macdonald (2000), the role
of attention in the tasks that involve inhibition of automatic responses is to select an
appropriate response out of two competing processes. The level of attention required
mainly depends on two factors: the strength of the automatic pathway and the strength of
a competing pathway (Cohen et al., 1990). The automatic pathway, which is considered a
stronger pathway, requires less attention than a competing pathway (Cohen et al., 1990).
Although it is intuitive that attention is significant during the inhibition of automatic
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22
responses, the specific mechanism of attention and its relation to inhibition remain
elusive. Engle and Kane (2003) proposed the two-factor model, which hypothesizes that
differences in executive attention contribute to the performance differences during
inhibition tasks. According to the two-factor model, executive attention has two major
functions- to retain information in active memory and to resolve a conflict between taskappropriate responses and automatic inappropriate responses (Engle & Kane, 2003). This
model also speculates that there are respective brain areas for these two functions: the
prefrontal cortex, which is responsible for maintenance of relevant active information and
the anterior cingulate, which is responsible for a conflict resolution. Interestingly, these
brain areas, which according to the two-factor model are involved in attention, have been
implicated in Prepotent Response Inhibition (Band & Boxtel, 1999; Macleod &
Macdonald, 2000; Oldrati et al., 2016). This demonstrates that brain-imaging studies
might lead to various interpretations in which the same brain region might contribute to a
variety of different cognitive processes.
As mentioned above, the two-factor model states that attention is important for
good performance on the inhibition tasks and this hypothesis is supported by some
empirical evidence (Verbruggen, Stevens, & Chambers, 2014; Wang, Tian, Wang, &
Benson, 2013). These studies have shown that increased focused attention results in the
improved inhibition performance while attention dislocation leads to poor performance.
However, other researchers have found that in some cases a decrease in attention
enhances performance on inhibition tasks (Kahneman & Henik, 1981; Scalzo, O’Connor,
Orr, Murphy, & Hester, 2016). For example, Kahneman and Henik (1981) have shown
that performance on the Stroop task improved when attention was not allocated to this
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23
process but was instead devoted to the interfering shapes. These discrepant findings
demonstrate that the attention mechanism might vary depending on the paradigm and
methodology. In some situations, attention is critical for good inhibition performance
while in other situations the lack of attention contributes to enhanced performance on
these same tasks. Nevertheless, all of these findings support the idea that inhibition and
attention may be closely related and it is important to consider the role of attention in any
inhibition paradigm.
Impulsivity
Another question that remains unanswered is whether inhibition is situational
action or is it a distinguishing part of one’s behavior, also known as a trait. One of the
traits that might be closely related to the failure to inhibit prepotent responses is
impulsivity (Logan, Schachar, & Tannock, 1997). There are various definitions of
impulsivity, for example, according to Reynolds, Ortengren, Richards, and Wit (2006)
impulsivity can be defined as being impatient, acting without thinking, not caring about
consequences, and lacking self-control. By looking at this definition, it is important to
realize that impulsivity is a multidimensional construct, which means that it consists of
several factors. For instance, the model proposed by Whiteside and Lynam (2001) states
that impulsivity consists of four factors: urgency, sensation seeking, lack of
premeditation, and lack of perseverance. Another model of impulsivity that was
presented by Patton, Stanford, and Barratt (1995) includes such factors as Motor
Impulsiveness, Non-Planning Impulsiveness, and Attentional Impulsiveness.
Many of the studies that investigated the association between Prepotent Response
Inhibition and impulsivity used the Barratt Impulsiveness Scale (Aichert et al., 2012;
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
24
Enticott, Ogloff, & Bradshaw, 2006; Logan et al., 1997). These studies looked at the
relationship between Impulsivity and such Prepotent Response Inhibition tasks as the
Antisaccade, the Stop Signal, and the Stroop tasks (Table 2). For example, Logan and
colleagues tested the association between the Stop Signal task and impulsivity and found
that subjects who were more impulsive had the longer stop-signal reaction times, which
indicates poorer inhibition skills (Logan et al., 1997). In contrast, Taylor (2016) looked at
the relationship between antisaccade performance and impulsivity scores and found no
significant relationship between impulsivity and antisaccade errors or impulsivity and
antisaccade reaction time. Similarly, Enticott and colleagues (2006) looked at the
correlation among several measurements of inhibition, including the Stroop task and Stop
Signal task; their results demonstrated that Stroop performance correlated significantly
with impulsivity, however they didn't find any significant relationship between
impulsivity and the Stop Signal task (Enticott et al., 2006). Aichert et al. study examined
the relationship among the Barratt Impulsiveness Scale (BIS) scores and the Antisaccade,
Stroop, Stop-signal, and Go/no-go tasks. The authors detected a significant correlation
between BIS impulsivity scores and errors on the Antisaccade task, which conflicts with
Taylor’s findings described above. In addition, Aichert and colleagues (2012) were
unable to find significant correlations between the Stroop performance and impulsivity or
between the Stop Signal task and impulsivity, which contradicts findings by Logan et al.
and Enticott et al.
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25
Such inconsistencies might occur because of several reasons. One of them is
differences in methodologies across all the studies. Many of these studies used different
versions of inhibition tasks as well as impulsivity scales. An additional reason might be
that failure to inhibit responses does not reflect that a person is impulsive. It might not be
a part of a person’s character but just a part of a situational state. One of the goals of my
study is to contribute to understanding of how impulsivity and Prepotent Response
Inhibition are related and how each of the inhibition tasks is correlated with impulsivity.
Caffeine effect
Although it is important to investigate the nature of the inhibition construct, it is
also important to learn which factors can affect inhibition performance. Multiple studies
have tested how inhibition performance is altered through pharmacological manipulations
with such substances as nicotine (Wignall & Wit, 2011), cannabis (Mokrysz, Freeman,
Korkki, Griffiths, & Curran, 2016), and methamphetamine (Monterosso, Aron, Cordova,
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
26
Xu, & London, 2005). One of the aims of my study is to assess how caffeine affects
performance on the inhibition tasks. In North America, about 90% of adults consume
caffeine on a daily basis (Heckman, Weil, & De Mejia, 2010). Coffee, tea, chocolate,
soda - they all contain caffeine in various amounts. Caffeine is a natural alkaloid derived
from beans, leaves, and fruits (Heckman et al., 2010). At the molecular level, caffeine
acts as an adenosine receptor antagonist because of its similarity to adenosine (Heckman
et al., 2010). There are two adenosine receptor types to which caffeine binds - A1 and
A2a. The A1 receptors are mostly found in the hippocampus, cerebral cortex, cerebellar
cortex and thalamic nuclei, while the A2a receptors are located in the brain areas with
high dopamine concentration (Heckman et al., 2010). When caffeine binds to those
receptors it prevents adenosine from binding which in turn halts the sleep effect induced
by adenosine.
The binding of caffeine to these receptors leads to alterations in human cognitive
and behavioral functions. Various studies have demonstrated that caffeine has an impact
on such functions as information processing (Tieges, 2004), task switching (Tieges et al.,
2006), and attention (Haskell, Kennedy, Milne, Wesnes, & Scholey, 2008; Hewlett &
Smith, 2006). The question that is most important for the purposes of this study is what
effect does caffeine have on Prepotent Response Inhibition? There are some conflicting
results throughout the literature. For example, Tieges and colleagues (2009) looked at the
effect of caffeine on the Stop Signal task and the Eriksen Flanker task and found no
significant impact of caffeine on inhibition. Since this study had a very small sample size,
the lack of caffeine effect might be interpreted as Type II error. In contrast, Addicott and
Laurienti (2009) discovered a significant effect of caffeine on the performance on the
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27
Eriksen Flanker task. Similarly, a different study found a significant impact of caffeine
on Stroop test performance (Kenemans, Wieleman, Zeegers, & Verbaten, 1999).
Although the effect of caffeine has been assessed in the context of the Stop Signal task
and the Stroop task, the effect of caffeine has not been tested yet by using the
Antisaccade paradigm.
The present study looked at the effect of caffeinated energy drinks on Prepotent
Response Inhibition. One of the reasons why pure caffeine was not selected as an
independent variable is because of ecological validity. Most people rarely take caffeine in
its pure form (Mitchell, Knight, Hockenberry, Teplansky, & Hartman, 2014). Therefore, I
decided to test how caffeine in energy drinks would affect inhibition. One of the concerns
of the study was that an energy drink contains many other active components such as
amino acids, herbal extracts, and vitamins, which might cause some changes in behavior
and not the caffeine itself. Childs (2014) reviewed whether various components in energy
drinks interact with caffeine to affect cognitive performance and found that the
components didn’t have a significant effect, however, more research should be done to
support this claim (Childs, 2014). In order to ensure that caffeine is the only variable that
would affect differences in the behavior of participants, the control group received a
decaffeinated energy drink which had similar content except it lacked caffeine.
The goal of my study was to determine how caffeine affects the following
inhibition measures: the Antisaccade task, the Stroop task, the Stop Signal task, and the
Eriksen Flanker task. Additionally, the effect of caffeine was tested on the Rapid Visual
Information Processing Attention task, since it has been established by many studies that
caffeine positively affects the performance on this task (Einöther & Giesbrecht, 2012).
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28
By using caffeine as my independent variable, I sought to establish whether performance
on the Prepotent Response Inhibition tasks could be altered through pharmacological
manipulations.
Present Study
The current study had three main aims. The first goal was to determine whether
there is a correlation among the three Prepotent Response Inhibition tasks. My
expectation was to detect the strongest correlation between the Antisaccade task, the
Stroop task, and the Stop Signal task and to find that performance on the Prepotent
Response Inhibition tasks correlates less well with the Eriksen Flanker task. The
rationale behind this expectation was that according to Friedman and Miyake (2004), the
Antisaccade task, the Stroop task, and the Stop Signal task belong to the same inhibition
category while the Eriksen Flanker task belongs to a related, but nevertheless different
inhibition category (Resistance to Distractor Interference). In addition, I assessed the
correlation between the Stroop task and the Flanker task in order to learn to which
inhibition category the Stroop task should belong. Lastly, I hypothesized that there would
be a significant correlation between performance on the inhibition tasks and the attention
task since attention seems to be an underlying component for all of these tasks.
The second goal was to determine whether there is a correlation between the
personality trait of impulsivity and performance on the inhibition tasks. My expectation
was to observe a significant relationship between impulsivity and poor performance on
the inhibition tasks because impulsive individuals are expected to be more likely to
exhibit difficulties in inhibiting prepotent responses.
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29
The final goal was to investigate whether caffeinated energy drinks have an effect
on Prepotent Response Inhibition and attention. I hypothesized that caffeine should
enhance performance on the inhibition tasks because there are several studies that have
shown a positive impact of stimulants, such as caffeine and nicotine, on inhibition
(Addicott & Laurienti, 2009; Bowling & Donnelly, 2010; Kenemans et al., 1999; Provost
& Woodward, 1991). Additionally, I hypothesized that caffeine should enhance
performance on the attention task because it has been previously established that caffeine
enhances attention (Einöther& Giesbrecht, 2012). Also, I sought to test whether the
effects of caffeine are dose-dependent by using the three dosages - 200 mg, 103 mg, and
6 mg. I hypothesized that if there would be an effect of caffeine, then higher caffeine
dosage should have a stronger impact on the performance of inhibition and attention
tasks.
Method
Participants
Sixty-six Lake Forest College students (45 females and 20 males) 18-25 years of
age participated in this study. The racial composition of my sample was the following:
54.5% White, 6.1 % African American, 13.6 % Asian/Pacific Islander, 19.7 %
Hispanic/Latino, and 6% Other. Only people who had no contraindication to energy
drinks were allowed to participate in this study. Prior to participating all participants
signed a written consent form. Students who were recruited from psychology classes
were compensated with extra-credit. The study was approved by the Human Subjects
Review Committee of Lake Forest College. All of the forms, which include the Informed
Consent and the Debriefing Sheet, might be found in the Appendix.
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30
Measures
Prosaccade and Antisaccade tasks
These tasks were adapted and modified from the Friedman and Miyake (2004)
study. During the task, participants saw a fixation point on the middle of the screen and
then a cue, a black square, appeared either to the left or to right of the fixation point (the
visual angle in this study was approximately 1.2 °). After 175 ms the cue disappeared
and a target stimulus appeared at the opposite location for 150 ms. The target stimulus
contained a box with an arrow inside. After, the target was masked with gray crosshatching until the participant pressed an arrow key to indicate in which direction the
arrow was pointing. There were five blocks of 20 trials, where the first two blocks were
the Prosaccade task (cue and target appeared at the same location) and the remaining 3
blocks were the Antisaccade task. Thus, the Prosaccade task contained 40 trials and the
Antisaccade task contained 60 trials. The dependent measures included prosaccade
reaction time (RT), antisaccade RT, prosaccade error percentage, and antisaccade error
percentage.
Stroop Task
This task was adapted and modified from the Friedman and Miyake (2004) paper.
The task consisted of three blocks and each block contained 60 trials. All trials were
presented on a computer monitor in front of the participant. During the first block for
each trial, a string of asterisks was presented in which the asterisks were printed in one of
six colors: blue, green, orange, purple, red, and yellow. The length of each asterisk string
matched the length of the color word describing the asterisk string. For example, the
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31
asterisk string for the word “blue” looked like ****. The second block contained 60 trials
with a neutral word printed in one of the six colors. The neutral words were the
following: lot, ship, cross, advice, intent, and debate. According to Friedman and Miyake
(2004), these words were selected to be the same length, number of syllables, and
frequency as the color words. For example, the word “red” corresponds to the word ‘lot’
while “green” corresponds to “cross” The third block contained a color word printed in a
different ink color and participants were asked to respond to the color of the ink rather
than the name of the color word. For example, when participants saw the word red
printed in blue they had to respond to the blue ink color and not printed word red. During
this task, participants saw the stimulus (either words or asterisk strings) that appeared in
the middle of the screen. Participants had to name the color of the stimulus and in order
to proceed to the next trial they had to press the right arrow key. The dependent measures
for the Stroop task included the response time of the trials in which the word and the
color were incongruent (Stroop Incongruent RT) and the response time of the trials which
consisted of neutral words (Stroop Neutral RT).
Stop Signal Task
The Stop Signal task was adapted and modified from the Friedman and Miyake
(2004) paper. The Stop Signal task consisted of five blocks of trials. The first two blocks
contained 48 trials used in order to create a prepotent categorization response. During this
phase, participants were asked to categorize a word presented on the screen as a sport or
not. Then, in the next three blocks of 50 trials each, participants were asked to inhibit the
sport/non-sport response when they saw a stop sign which occurred on approximately
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32
30% of the trials. On all trials, participants had to look at the fixation point for 500 ms
and then the stimulus appeared in the place of the fixation point. They were given up to
1,500 ms to categorize the target word by pressing either the left (sport) or right (nonsport) arrow key. In the stop signal trials, the stop sign appeared on the screen 100 ms
after the word was presented. The dependent measures for the Stop Signal task included
the reaction time during the “go” trials (Go RT) and the reaction time during the “stop”
trials (Stop RT).
Eriksen Flanker task
The Eriksen Flanker task was adapted and modified from the Friedman and
Miyake (2004) paper. In this task participants were instructed to respond to a particular
target letter at the center of the monitor and ignore any other letters around the target
letter. Participants had to press the right arrow key when the target letter was H or K, and
left arrow key when the target letter was C or S. There were four conditions: 1)
Interfering letters were the same as the target (HHHHHHH); 2) Interfering letters were
compatible with the target in that they required the same arrow key responses
(KKKHKKK); 3) Interfering letters were incompatible with the target in that they
required the different arrow key responses (SSSHSSS); 4) No interfering letters (only H
was presented). There was a total of 160 trials with 40 trials for each of the four
conditions. There was a break of 20 seconds between each of the four conditions. During
each trial, there was a fixation point on the white screen and then a target letter appeared
after 500 ms. Participants were given up to 1500ms to respond to the stimulus. The main
dependent measures included reaction time in the no-interfering condition, reaction time
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33
in the incompatible condition, percent error in the no-interfering condition, and percent
error in incompatible condition.
Rapid Visual Information Processing Attention task
The procedural steps were adapted and modified from the Smit and Rogers (2000)
paper. During this task a sequence of numbers ranging from 1 to 9 appeared in random
order in the middle of the computer screen. Participants were asked to press a space bar
when they detected a sequence of three odd numbers (e.g. 1-3-5, 3-5-7, 5-7-9). Each
number was presented for 600 ms. During each minute 8 target sequences were presented
and there was a break of 20 seconds after each minute. The task lasted for 5 minutes
therefore participants had to detect 40 target sequences during the task. The dependent
measures for this task were the percentage of correct responses and the mean reaction
time for correct responses.
Impulsivity Scale
The impulsivity scale used in this study was the Barratt Impulsiveness Scale (BIS
11) found in the paper by Patton et al. (1995). The Barratt Impulsiveness Scale has 30
statements, which assess three types of Impulsivity- Attentional, Motor, and
Nonplanning. This is the Likert type scale that includes some reverse-keyed items. In
order to compute the total impulsivity score I added up all of the ratings for each item. To
establish the reliability and internal consistency of the Impulsivity scores I used
Cronbach’s Alpha. The Cronbach’s Alpha value was 0.840, which indicates that this
measure is reliable. In addition to examining the relationship between inhibition
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34
performance and total impulsivity score I also decided to look at the relationship between
inhibition and the Motor function of impulsivity. I decided to examine the Motor function
because all of my tasks involved a motor response. A copy of the BIS 11 can be found in
the Appendix.
Demographic/Caffeine Consumption Questionnaires
A demographic questionnaire was used to determine the diversity of the studied
sample. The caffeine consumption questionnaire was used in order to determine habitual
caffeine usage of participants and to test whether participants in the three experimental
groups were significantly different from each other in terms of their caffeine
consumption. A caffeine consumption scale adapted and modified from the Landrum
(1992) paper assessed caffeine related habits of the participants. I did not find any
significant differences between groups in terms of their caffeine consumption (F (2, 63)
=0.473, p=.625). Copies of these questionnaires can be found in the Appendix.
Equipment
The equipment I used in this study included two computers where one was used to
present tasks to participants and the second computer was used to track and observe eye
movements. Next to the first computer, an ISCAN infrared corneal reflection eye tracker
system was located which was employed to track participants’ eye movements. A video
camera was used to record participants while they performed the Antisaccade and the
Stroop tasks. In order to program the tasks the software Psychology Software Tools, Inc.
[E-Prime 2.0] was employed and the SPSS software was used for the data analysis.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
35
Procedure
Prior to the study, participants were randomly assigned to one of three groups.
One of the groups was a control group in which participants consumed a decaffeinated
energy drink. The other two groups were the experimental conditions in which
participants consumed energy drinks with the caffeine contents of 200 mg and 103mg,
respectively. During the experiment day, after completing the informed consent, the
participants were asked to consume the assigned drink. After participants consumed their
drink, they had a rest period of 45 minutes, during which participants completed the
Demographic/Caffeine Consumption Questionnaire and the Barratt Impulsiveness Scale
(BIS 11). After participants completed the surveys, they worked on their homework.
After 45 minutes elapsed, the battery of inhibition tasks and one attention task were
presented to the participants in a random order. Inhibition tasks included the Antisaccade
task, the Stop Signal task, the Stroop test, and the Flanker Eriksen task. The sustained
attention task used in this study was the Rapid Visual Information Processing (RVIP)
task. Participants were video recorded while they were taking the Antisaccade and the
Stroop tasks. After completion of all of the tasks, the participants were debriefed and
thanked for participation.
Results
Table 3 shows the means and standard deviations for the Prepotent Response
Inhibition (PRI) measures as well as for the Flanker task, the Rapid Visual Information
Processing (RVIP) task and the Impulsivity Scale. The table demonstrates that there was
a difference between the inhibitory conditions and the non-inhibitory conditions for all of
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
36
the PRI tasks and for the Flanker task. While for the Antisaccade task, the Stroop task,
and the Flanker task the inhibitory conditions exhibited longer reaction times and greater
percent errors, for the Stop Signal task the non-inhibitory condition demonstrated faster
reaction times compared to the inhibitory condition. In order to test whether differences
between inhibitory condition vs no-inhibitory condition for the PRI tasks and the Flanker
task were significant paired sample t-tests were employed. Table 4 shows that there were
statistically significant differences between the Prosaccade RT and the Antisaccade RT
(p<0.05), the Prosaccade percent error and the Antisaccade percent error (p<0.05), the
Stroop neutral RT and the Stroop incongruent RT (p<0.05), and the Flanker incompatible
RT and the Flanker no-interfering RT (p<0.05). There was no statistically significant
difference between the Flanker incompatible percent error and no-interfering percent
error (p=0.486). Although there was a statistically significant difference between the Stop
Signal Go condition and Stop condition, this difference was opposite what I anticipated
which means that the Stop Signal task did not work as expected. Therefore, I will not use
the Stop Signal task results for my further analysis.
In order to determine whether the distribution for each of the 15 variables was
normal I employed Q-Q plots and the Kolmogorov-Smirnov Test. The following seven
distributions did not deviate significantly from normality: Impulsivity scores,
Antisaccade RT, Flanker incompatible RT, Flanker no-interfering RT, RVIP percentage
correct, RVIP RT, and the Stroop incongruent RT. The remaining eight variables were
not normally distributed. In order to normalize the skewed distributions, I transformed the
variables by using a log transformation. However, analyses on the log transformed data
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
37
did not lead to any differences in results compared to the non-transformed data; therefore,
I decided to report only results based on the original data.
Correlations
Table 5 shows the correlations among the Prepotent Response Inhibition, Eriksen
Flanker, Attention and Impulsivity variables. While looking at the associations within
Prepotent Response Inhibition I found no significant correlations among the PRI tasks. In
other words, the Antisaccade variables and the Stroop variables did not correlate. In
contrast, after examining correlations between different inhibition types, I found
significant correlations between the PRI tasks and the Eriksen Flanker task. For example,
the Antisaccade RT positively correlated with the Flanker incompatible RT (r=0.579,
p<0.05) and the Stroop incongruent RT correlated with the Flanker incompatible percent
error (r=0.275, p<0.05).
Whilst looking at the relationship between the attention and inhibition tasks I
found a significant correlation between the Antisaccade task and the RVIP task and the
Flanker task and the RVIP task. For example, the Antisaccade RT positively correlated
with the RVIP RT (r=0.308, p<0.05) and negatively correlated with the RVIP percent
correct (r=-0.452, p<0.05), while the Flanker incompatible RT positively correlated with
RVIP RT (r=0.283, p<0.022). There were no significant correlations between the Stroop
task and the RVIP task.
No tests were significantly correlated with the total Impulsivity score. However,
the Motor function of the Impulsivity Scale was significantly correlated with the Stroop
incongruent RT (r=-0.243, p<0.05).
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38
The Effect of Caffeinated Energy Drinks
In order to test whether caffeine affected performance on the administered tasks I
employed One-Way ANOVAs (Table 6). There was no significant effect of caffeine on
any of the Prepotent Response Inhibition tasks nor the Flanker task. However, caffeine
had a significant effect on the RVIP RT (F (2, 63) = 3.30, p<0.05, η 2=0.095). After
running the Tukey HSD test, I determined that there was a statistically significant
difference between the maximum caffeine group and the decaffeinated group. The test
demonstrated that participants in the maximum caffeine group had significantly lower RT
compared to the decaffeinated group (Figure 1).
Discussion
The current study examined the correlations among the Prepotent Response
Inhibition tasks and their associations with the Eriksen Flanker task, an attention task,
and a self-reported measure of trait impulsivity. In addition, I tested the effect of caffeine
on performance on inhibition and attention tasks. There are several key findings in my
study. Although I hypothesized that the Prepotent Response Inhibition tasks should be
highly correlated, I found no significant correlations between two of them, namely the
Stroop task and the Antisaccade task. The third PRI task did not work as expected and
was dropped as a consequence. In contrast, there were significant correlations between
the Eriksen Flanker task and both, the Antisaccade task and the Stroop task, which was
the opposite of what I expected; since according to Friedman and Miyake, the Eriksen
Flanker task belongs to the Resistance to Distractor Interference category and should not
be highly correlated with measures of the Prepotent Response Inhibition category.
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39
While investigating the relationship between inhibition and attention I found that
the Eriksen Flanker and the Antisaccade tasks significantly correlated with the attention
task and Stroop did not. In addition, there were no significant correlations between
impulsivity scores and inhibition tasks. However, when the Motor dimension of
impulsivity score was tested I detected a positive significant correlation between the
Motor Impulsivity and the Stroop task. Lastly, I failed to find a significant effect of
caffeine on the inhibition tasks but there was an impact on attention. My study found that
caffeine enhances attention, which supports some of the previous findings (Einöther &
Giesbrecht, 2012). There are several interpretations of my study, which I will discuss
next.
My study did not support the model proposed by Friedman and Miyake since
there were no significant correlations among tasks that belong to the Prepotent Response
Inhibition category. The failure to detect significant correlations might be explained by
two major reasons: 1) Type II error or 2) Friedman and Miyake’s model is fallacious and
tasks, which are suggested to belong to the same inhibition category, are not associated
with one another.
Type II error might be a reasonable cause why I could not find significant
correlations between the Prepotent Response Inhibition tasks for several reasons. My
study had a low power because there was a relatively small number of participants.
Furthermore, my experimental design could have contributed to the inability to find
hypothesized results. In particular, the version of the Stop Signal task I employed did not
work the way it was intended to work. In theory, the Stop blocks of this task should have
led to inhibition in participants, therefore, the participants should have exhibited longer
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
40
reaction times compared to the Go blocks, but the opposite of what I expected occurred.
That is the reaction times for the Stop blocks were significantly faster compared to the
Go blocks. I adapted this version of the task from the Friedman and Miyake’s paper
where they used an auditory stop signal but because of software issues, I had to use a
visual stop signal. This procedural change could have resulted in the failure to produce
the desired manipulation. This assumption might be supported by Schoot and colleagues
(2005), who demonstrated that the auditory and visual stop signals lead to differences in
Stop Signal performance. This might indicate that changes in the experimental design
was one of the possible explanations of why my version of the Stop Signal task did not
work.
In addition, I employed a version of the Antisaccade task that involved a motor
response of pressing buttons on the keyboard and many participants found this version of
the Antisaccade task very challenging. Interestingly, although many participants found it
challenging the error percent for my Antisaccade version was 20 %, which is a common
percent error for the Antissacade task. I decided to use this version of the task for two
major reasons: 1) it challenged participants and made them stay focused in order to
respond by a key press; 2) it allowed me to obtain reaction times and percent errors more
accurately and objectively because the computer software registered these measurements.
However, there are a few problems associated with such an experimental design. The
Antisaccade task is not a robust task which means that performance depends on how this
task is administered, for example, on how stimuli are presented, etc. (Fischer & Weber,
1997). This suggests that my version of the task may not have correlated with the Stroop
task because it was a variation of the Antisaccade task. Thus, if I used a simpler version
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
41
of the Antisaccade task, which did not involve key pressing, it could have led to different
results. However, one of the dangers of using a simple version of the Antisaccade task is
that it might lead to the floor effect since participants might find it very easy to do.
If we assume that my results reflect the true state of affairs, and not just a Type II
error or poor implementation of the inhibitory tasks, then there are some major
implications of this study. The absence of a correlation between the Stroop task and the
Antisaccade task might indicate that Prepotent Response Inhibition is not a unitary
construct. Although the Prepotent Response Inhibition tasks are conceptually similar and
have the common goal of inhibiting automatic responses, my study suggests that some
specific task characteristics might contribute to the absence of anticipated correlations.
These tasks involve different components; for example, the Antisaccade task involves
perceiving visuospatial information and responding by pressing an appropriate key, while
the Stroop task requires verbally naming the color of the words and the Stop Signal tasks
involves categorization of words. Such differences between tasks could have resulted in
different working memory loads and attention levels, which then influenced the overall
performance of subjects on the tasks.
Interestingly, the Eriksen Flanker task, which was not supposed to correlate with
the Prepotent Response Inhibition tasks, was significantly associated with both the
Antisaccade task and the Stroop task. This might indicate that some inhibition
mechanisms of the Eriksen Flanker task overlap with the inhibition mechanisms of the
Antisaccade task and similarly, there might be some common inhibition pathways for the
Eriksen Flanker and the Stroop tasks. Thus, such findings challenge the model proposed
by Friedman and Miyake (2004).
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42
My study also looked at attention and its association with the Prepotent Response
Inhibition tasks. I found a significant correlation between the Antisaccade task and the
attention task, however there was no significant correlations between the Stroop task and
the attention task. As I mentioned before inhibition is a multidimensional construct - it
consists of various components such as perception, attention, working memory, etc.
Therefore, some of the inhibition tasks might require different amounts of one component
over another; in this case, more attention might be required for the Antisaccade but not
that much for the Stroop task. However, there is an alternative explanation for this
finding. The attention task, which I used in my study, is thought to represent sustained
attention (Neale, Johnston, Hughes, & Scholey, 2015). It is important to take into account
that there are different types of attention (e.g. selective, divided, and executive) which
means that the Antisaccade task might rely on the sustained attention while the Stroop
tasks might rely on the selective or divided attention. This suggests that inhibition and
attention are both multidimensional tasks and therefore the pattern of correlations among
these tasks is likely to be complicated. Future studies are required to test this assumption.
My study did not find any significant correlations among impulsivity and
Prepotent Response Inhibition tasks, which suggests that inhibition is situational action
and not a part of one’s character. However, the Motor dimension of impulsivity
negatively correlated with the Stroop task, which means that people who have a higher
motor impulsivity score take less time to perform the Stroop task. The fact that the
Motor dimension correlates only with the Stroop task and not with the Antisaccade
emphasizes that these two do not share common inhibition mechanisms and might belong
to two different inhibition categories. My results are consistent with the previous findings
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
43
that did not detect significant relationships between Prepotent Inhibition tasks and
impulsivity (Aichert et al., 2012; Taylor, 2016). However, it is important to realize that
similarly to inhibition and attention, impulsivity is a multidimensional construct. This
means that some specific dimensions of impulsivity might be related to some specific
dimensions of inhibition, which might result in a complex pattern of correlations.
Lastly, as I stated above, my study did not find any significant impact of the
caffeinated energy drinks on the Prepotent Response Inhibition tasks or the Eriksen
Flanker task; however, caffeine had an effect on attention. Such a finding might have
several major implications. First, the lack of the caffeine effect on inhibition performance
contradicts other studies which have demonstrated that stimulant drugs improved
performance on inhibition tasks (Addicott & Laurienti, 2009; Bowling & Donnelly, 2010;
Kenemans et al., 1999; Provost & Woodward, 1991). However, other studies that tested
the caffeine effect have demonstrated mixed results, which means that the impact of
caffeine on inhibition is still not well established. One of the reasons why my study did
not detect the influence of caffeine on inhibition might be that participants could have
had high baseline performance on the inhibition tasks, which means that the caffeine
manipulation would not result in significant improvements due to a ceiling effect. In
order to check this assumption I compared the average performance on the inhibition
tasks to the maximum and minimum scores in my study. For example, in the Antisaccade
task the mean reaction time was 394 ms while the fastest RT in my study was 257 ms,
which demonstrates that participants can improve their performance on this task.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
44
Still, it would be interesting to test participants prior to the caffeine administration,
determine their baseline performance, and then see whether people with high baseline
performance improve their performance even more after the caffeine administration.
The fact that caffeine enhanced attention performance but had no effect on
inhibition might suggest that attention and inhibition are not closely related to one
another and might be regulated by different neuronal pathways. If attention was part of
inhibition, the change in attention should also result in some changes in inhibition
performance; however, this was not observed. One of the possible reasons why such
interaction was not detected might be because my crude measures could not pick apart
subtle overlaps and differences among the tasks. An alternative explanation might be that
attention plays a minor role in Antisaccade task and that is why alterations in attention in
the caffeine condition did not influence performance on the inhibition task. Additionally,
as I mentioned before Type II error might be the reason why I did not find a significant
effect of caffeine on inhibition performance.
There are several changes, which I would implement in order to improve my
study. First, I would change the administration of the Stop Signal task and I would use an
auditory stop signal. Additionally, I would use the pure form of caffeine to ensure that
extraneous ingredients in energy drinks will not interfere with the caffeine effect.
One of the possible future studies might include studying the relationship among
Resistance to Proactive Interference and other inhibition categories. Since according to
Friedman and Miyake, Resistance to Proactive Interference is weakly related to both,
Prepotent Response Inhibition and Resistance to Distractor Interference, I would expect
to find low correlations between Resistance to Proactive Interference and two other
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
45
inhibition categories. Another possible future study would be to investigate correlations
among different version of the Antisaccade task, Stroop tasks, and Stop Signal task to
determine how robust the tasks and correlations are.
To conclude, I examined the associations among the Prepotent Response
Inhibition tasks and did not find significant correlations. However, I found significant
associations between the Prepotent Response Inhibition tasks and the Resistance to
Distractor Interference task, which does not support the model proposed by Friedman and
Miyake. Also, my study didn’t detect the hypothesized relationship between impulsivity
and inhibition performance. Lastly, my study failed to find the effect of caffeine on
inhibition performance. More studies with a large number of participants and more
standardized procedures are required to test the validity of the model proposed by
Friedman and Miyake and to reveal the underlying components of inhibition.
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46
References
Abegg, M., Sharma, N., & Barton, J. J. (2012). Antisaccades generate two types of
saccadic inhibition. Biological Psychology, 89(1), 191-194.
doi:10.1016/j.biopsycho.2011.10.007
Addicott, M. A., & Laurienti, P. J. (2009). A comparison of the effects of caffeine
following abstinence and normal caffeine use. Psychopharmacology, 207(3), 423431. doi:10.1007/s00213-009-1668-3
Aichert, D. S., Wöstmann, N. M., Costa, A., Macare, C., Wenig, J. R., Möller, H., . . .
Ettinger, U. (2012). Associations between trait impulsivity and prepotent response
inhibition. Journal of Clinical and Experimental Neuropsychology, 34(10), 10161032. doi:10.1080/13803395.2012.706261
Aron, A. R., Robbins, T. W., & Poldrack, R. A. (2004). Inhibition and the right inferior
frontal cortex. Trends in Cognitive Sciences, 8(4), 170-177.
doi:10.1016/j.tics.2004.02.010
Band, G., & Boxtel, G. V. (1999). Inhibitory motor control in stop paradigms: review and
reinterpretation of neural mechanisms. Acta Psychologica, 101(2-3), 179-211.
doi:10.1016/s0001-6918(99)00005-0
Barton, J. J., Greenzang, C., Hefter, R., Edelman, J., & Manoach, D. S. (2005).
Switching, plasticity, and prediction in a saccadic task-switch
paradigm. Experimental Brain Research, 168(1-2), 76-87. doi:10.1007/s00221-0050091-1
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
47
Beech, A., Powell, T., McWilliam, J. and Claridge, G. (1989). Evidence of reduced
‘cognitive inhibition’ in schizophrenia. British Journal of Clinical Psychology, 28(2),
109–116. doi:10.1111/j.2044-8260.1989.tb00821.x
Benedek, M., Franz, F., Heene, M., & Neubauer, A. C. (2012). Differential effects of
cognitive inhibition and intelligence on creativity. Personality and Individual
Differences, 53(4), 480-485. doi:10.1016/j.paid.2012.04.014
Boucher, L., Palmeri, T. J., Logan, G. D., & Schall, J. D. (2007). Inhibitory control in
mind and brain: An interactive race model of countermanding saccades.
Psychological Review, 114, 376–397. doi:10.1037/0033-295X .114.2.376
Bowling, A. C., & Donnelly, J. F. (2010). Effect of nicotine on saccadic eye movement
latencies in non-smokers. Human Psychopharmacology: Clinical and Experimental,
25(5), 410-418. doi:10.1002/hup.1134
Carvalho, N., Noiret, N., Vandel, P., Monnin, J., Chopard, G., & Laurent, E. (2014).
Saccadic eye movements in depressed elderly patients. PLoS ONE, 9(8).
doi:10.1371/journal.pone.0105355
Chevrier, A. D., Noseworthy, M. D., & Schachar, R. (2007). Dissociation of response
inhibition and performance monitoring in the stop signal task using event-related
fMRI. Human Brain Mapping, 28(12), 1347-1358. doi:10.1002/hbm.20355
Childs, E. (2014). Influence of energy drink ingredients on mood and cognitive
performance. Nutrition Reviews, 72, 48-59. doi:10.1111/nure.12148
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
48
Clair-Thompson, H. L., & Gathercole, S. E. (2006). Executive functions and
achievements in school: Shifting, updating, inhibition, and working memory. The
Quarterly Journal of Experimental Psychology, 59(4), 745-759.
doi:10.1080/17470210500162854
Cohen, J. D., Dunbar, K., & Mcclelland, J. L. (1990). On the control of automatic
processes: A parallel distributed processing account of the Stroop effect.
Psychological Review, 97(3), 332-361. doi:10.1037/0033-295x.97.3.332
Cohen-Gilbert, J. E., & Thomas, K. M. (2013). Inhibitory control during emotional
distraction across adolescence and early adulthood. Child Development, 84(6), 19541966. doi:10.1111/cdev.12085
Crawford, T. J., Parker, E., Solis-Trapala, I., & Mayes, J. (2010). Is the relationship of
prosaccade reaction times and antisaccade errors mediated by working memory?
Experimental Brain Research, 208(3), 385-397. doi:10.1007/s00221-010-2488-8
Curtis, C. E., & D'esposito, M. (2003). Persistent activity in the prefrontal cortex during
working memory. Trends in Cognitive Sciences, 7(9), 415-423. doi:10.1016/s13646613(03)00197-9
Davidson, D. J., Zacks, R. T., & Williams, C. C. (2003). Stroop Interference, Practice,
and Aging. Neuropsychology, Development, and Cognition. Section B, Aging,
Neuropsychology and Cognition, 10(2), 85–98
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
49
Duann, J.-R., Ide, J. S., Luo, X., & Li, C. R. (2009). Functional connectivity delineates
distinct roles of the inferior frontal cortex and pre-supplementary motor area in stop
signal inhibition. The Journal of Neuroscience : The Official Journal of the Society
for Neuroscience, 29(32), 10171–10179
Dunbar, K., & Macleod, C. M. (1984). A horse race of a different color: Stroop
interference patterns with transformed words. Journal of Experimental Psychology:
Human Perception and Performance, 10(5), 622-639. doi:10.1037//00961523.10.5.622
Eagle, D. M., Baunez, C., Hutcheson, D. M., Lehmann, O., Shah, A. P., & Robbins, T.
W. (2007). Stop-signal reaction-time task performance: role of prefrontal cortex and
subthalamic nucleus. Cerebral Cortex, 18(1), 178-188. doi:10.1093/cercor/bhm044
Einöther, S. J., & Giesbrecht, T. (2012). Caffeine as an attention enhancer: reviewing
existing assumptions. Psychopharmacology, 225(2), 251-274. doi:10.1007/s00213012-2917-4
Engle, R. W., & Kane, M. J. (2003). Executive Attention, Working Memory Capacity,
and a Two-Factor Theory of Cognitive Control. Psychology of Learning and
Motivation, 145-199. doi:10.1016/s0079-7421(03)44005-x
Enticott, P. G., Ogloff, J. R., & Bradshaw, J. L. (2006). Associations between laboratory
measures of executive inhibitory control and self-reported impulsivity. Personality
and Individual Differences, 41(2), 285-294. doi:10.1016/j.paid.2006.01.011
Everling, S., & Fischer, B. (1998). The antisaccade: A review of basic research and
clinical studies. Neuropsychologia, 36, 885–899.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
50
Fischer, B., & Weber, H. (1997). Effects of stimulus conditions on the performance of
antisaccades in man. Experimental Brain Research, 116(2), 191-200.
doi:10.1007/pl00005749
Friedman, N. P., & Miyake, A. (2004). The Relations Among Inhibition and Interference
Control Functions: A Latent-Variable Analysis. Journal of Experimental Psychology:
General, 133(1), 101-135. doi:10.1037/0096-3445.133.1.101
Fukushima, J., Fukushima, K., Chiba, T., Tanaka, S., Yamashita, I., & Kato, M. (1988).
Disturbances of voluntary control of saccadic eye movements in schizophrenic
patients. Biological Psychiatry, 23, 670–677.
Gorfein, D. S., & MacLeod, C. M. (2007). Inhibition in cognition. American
Psychological Association.
Hallett, P. E. (1978). Primary and secondary saccades to goals defined by instructions.
Vision Research, 18, 1279–1296.
Haskell, C.F., Kennedy D.O., Milne A.L., Wesnes K.A., Scholey A.B. (2008). The
effects of L-theanine, caffeine and their combination on cognition and mood. Biol
Psychol, 77, 113–122.
Heckman, M. A., Weil, J. and De Mejia, E. G. (2010). Caffeine (1, 3, 7trimethylxanthine) in foods: A comprehensive review on consumption, functionality,
safety, and regulatory matters. Journal of Food Science, 75, R77–R87.
doi:10.1111/j.1750-3841.2010.01561.x
Hewlett P., & Smith, A. (2006) Acute effects of caffeine in volunteers with different
patterns of regular consumption. Hum Psychopharmacol, 21, 167–180
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
51
Howard, S. J., Johnson, J., & Pascual-Leone, J. (2014). Clarifying inhibitory control:
Diversity and development of attentional inhibition. Cognitive Development, 31, 121. doi:10.1016/j.cogdev.2014.03.001
Hutton, S. B., & Ettinger, U. (2006). The antisaccade task as a research tool in
psychopathology: A critical review. Psychophysiology, 43(3), 302-313.
doi:10.1111/j.1469-8986.2006.00403.x
Jacob, G. A., Gutz, L., Bader, K., Lieb, K., Tüscher, O., & Stahl, C. (2010). Impulsivity
in borderline personality disorder: Impairment in self-report measures, but not
behavioral inhibition. Psychopathology, 43(3), 180-188. doi:10.1159/000304174
Johnston, K., Madden, A. K., Bramham, J., & Russell, A. J. (2010). Response inhibition
in adults with autism spectrum disorder compared to Attention Deficit/Hyperactivity
Disorder. Journal of Autism and Developmental Disorders, 41(7), 903-912.
doi:10.1007/s10803-010-1113-9
Kahneman, D., & Henik, A. (1981). Perceptual organization and attention. In M. Kubovy
& J.R. Pomerantz (Eds.), Perceptual organization (pp. 181-211). Hillsdale, NJ:
Erlbaum.
Kane, M. J., & Engle, R. W. (2000). Working-memory capacity, proactive interference,
and divided attention: Limits on long-term memory retrieval. Journal of Experimental
Psychology: Learning, Memory, and Cognition, 26, 336–358.
Kenemans J.L., Wieleman J.S., Zeegers M., & Verbaten M.N. (1999) Caffeine and
Stroop interference. Pharmacol Biochem Behav 63, 589–598.
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
52
Larsen, S., & Parlenvi, P. (1984). Patterns of inverted reading and subgroups in
dyslexia. Annals of Dyslexia, 34(1), 195-203. doi:10.1007/bf02663620
Livesey, D., Keen, J., Rouse, J., & White, F. (2006). The relationship between measures
of executive function, motor performance and externalising behaviour in 5- and 6year-old children. Human Movement Science, 25(1), 50-64.
doi:10.1016/j.humov.2005.10.008
Logan, G. D., & Cowan, W. B. (1984). On the ability to inhibit thought and action: A
theory of an act of control. Psychological Review, 91(3), 295-327. doi:10.1037//0033295x.91.3.295
Logan, G. D., Schachar, R. J., & Tannock, R. (1997). Impulsivity and inhibitory control.
Psychological Science, 8(1), 60-64. doi:10.1111/j.1467-9280.1997.tb00545.x
Long, D. L., & Prat, C. S. (2002). Working memory and Stroop interference: An
individual differences investigation. Memory & Cognition, 30(2), 294-301.
doi:10.3758/bf03195290
Macleod, C. M. (2015). The Stroop Effect. Encyclopedia of Color Science and
Technology, 1-6. doi:10.1007/978-3-642-27851-8_67-1
MacLeod, C. M. (1991). Half a century of research on the Stroop effect: An integrative
review. Psychological Bulletin, 109, 163–203.
Macleod, C. M., & Macdonald, P. A. (2000). Interdimensional interference in the Stroop
effect: uncovering the cognitive and neural anatomy of attention. Trends in Cognitive
Sciences, 4(10), 383-391. doi:10.1016/s1364-6613(00)01530-8
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
53
Massen, C. (2004). Parallel programming of exogenous and endogenous components in
the antisaccade task. The Quarterly Journal of Experimental Psychology Section A,
57(3), 475-498. doi:10.1080/02724980343000341
Matsuda, T., Matsuura, M., Ohkubo, T., Ohkubo, H., Matsushima, E., Inoue, K., Taira,
M. & Kojima, T. (2004). Functional MRI mapping of brain activation during visually
guided saccades and antisaccades: Cortical and subcortical networks. Psychiatry
Research, 131, 147–155.
Michel, F., & Anderson, M. (2009). Using the antisaccade task to investigate the
relationship between the development of inhibition and the development of
intelligence. Developmental Science, 12(2), 272-288. doi:10.1111/j.14677687.2008.00759.x
Mitchell, D. C., Knight, C. A., Hockenberry, J., Teplansky, R., & Hartman, T. J. (2014).
Beverage caffeine intakes in the U.S. Food and Chemical Toxicology, 63, 136-142.
doi:10.1016/j.fct.2013.10.042
Mitchell, J. P., Macrae, C. N., & Gilchrist, I. D. (2002). Working memory and the
suppression of reflexive saccades. Journal of Cognitive Neuroscience, 14, 95–103.
Mokler A, Fischer B (1999). The recognition and correction of involuntary prosaccades
in an antisaccade task. Experimental Brain Research, 125, 511–516.
Mokrysz, C., Freeman, T. P., Korkki, S., Griffiths, K., & Curran, H. V. (2016). Are
adolescents more vulnerable to the harmful effects of cannabis than adults? A
placebo-controlled study in human males. Translational Psychiatry, 6(11).
doi:10.1038/tp.2016.225
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
54
Monterosso, J. R., Aron, A. R., Cordova, X., Xu, J., & London, E. D. (2005). Deficits in
response inhibition associated with chronic methamphetamine abuse. Drug and
Alcohol Dependence, 79(2), 273-277. doi:10.1016/j.drugalcdep.2005.02.002
Munoz, D. P., & Everling, S. (2004). Look away: the anti-saccade task and the voluntary
control of eye movement. Nature Reviews Neuroscience, 5(3), 218-228.
doi:10.1038/nrn1345
Neale, C., Johnston, P., Hughes, M., & Scholey, A. (2015). Functional activation during
the rapid visual information processing task in a middle aged cohort: An fMRI
study. Plos One, 10(10). doi:10.1371/journal.pone.0138994
Nigg, J. T. (2000). On inhibition/disinhibition in developmental psychopathology: Views
from cognitive and personality psychology and a working inhibition taxonomy.
Psychological Bulletin, 126(2), 220-246. doi:10.1037//0033-2909.126.2.220
Nigg, J. T. (2001). Is ADHD a disinhibitory disorder? Psychological Bulletin, 127, 571–
598
Noël, X., Linden, M. V., Brevers, D., Campanella, S., Verbanck, P., Hanak, C., . . .
Verbruggen, F. (2013). Separating intentional inhibition of prepotent responses and
resistance to proactive interference in alcohol-dependent individuals. Drug and
Alcohol Dependence, 128(3), 200-205. doi:10.1016/j.drugalcdep.2012.08.021
Oldrati, V., Patricelli, J., Colombo, B., & Antonietti, A. (2016). The role of dorsolateral
prefrontal cortex in inhibition mechanism: A study on cognitive reflection test and
similar tasks through neuromodulation. Neuropsychologia, 91, 499-508.
doi:10.1016/j.neuropsychologia.2016.09.010
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
55
Patton, J. H., Stanford, M. S., & Barratt, E. S. (1995). Factor structure of the barratt
impulsiveness scale. Journal of Clinical Psychology, 51(6), 768-774.
doi:10.1002/1097-4679(199511)51:63.0.co;2-1
Pawliczek, C. M., Derntl, B., Kellermann, T., Kohn, N., Gur, R. C., & Habel, U. (2013).
Inhibitory control and trait aggression: Neural and behavioral insights using the
emotional stop signal task. NeuroImage, 79, 264-274.
doi:10.1016/j.neuroimage.2013.04.104
Potenza, M. N., Leung, H., Blumberg, H. P., Peterson, B. S., Fulbright, R. K., Lacadie, C.
M., . . . Gore, J. C. (2003). An fMRI Stroop task study of ventromedial prefrontal
cortical function in pathological gamblers. American Journal of Psychiatry, 160(11),
1990-1994. doi:10.1176/appi.ajp.160.11.1990
Provost, S. C., & Woodward, R. (1991). Effects of nicotine gum on repeated
administration of the stroop test. Psychopharmacology, 104(4), 536-540.
doi:10.1007/bf02245662
Rafal, R., & Henik, A. (1994). The neurology of inhibition: Integrating controlled and
automatic processes. In D. Dagenbach & T. H. Carr (Eds.), Inhibitory processes in
attention, memory, and language (pp. 1-51). San Diego, CA: Academic Press.
Reynolds, B., Ortengren, A., Richards, J. B., & de Wit, H. (2006). Dimensions of
impulsive behavior: Personality and behavioral measures. Personality and Individual
Differences, 40, 305-315. doi:10.1016/j.paid.2005.03.024
Scalzo, F., O’Connor, D. A., Orr, C., Murphy, K., & Hester, R. (2016). Attention
diversion improves response inhibition of immediate reward, but only when it is
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
56
beneficial: An fMRI study. Frontiers in Human Neuroscience,10.
doi:10.3389/fnhum.2016.00429
Schaeffer, D. J., Chi, L., Krafft, C. E., Li, Q., Schwarz, N. F., & Mcdowell, J. E. (2014).
Individual differences in working memory moderate the relationship between
prosaccade latency and antisaccade error rate. Psychophysiology, 52(4), 605-608.
doi:10.1111/psyp.12380
Schoot, M. V., Licht, R., Horsley, T. M., & Sergeant, J. A. (2005). Effects of stop signal
modality, stop signal intensity and tracking method on inhibitory performance as
determined by use of the stop signal paradigm. Scandinavian Journal of Psychology,
46(4), 331-341. doi:10.1111/j.1467-9450.2005.00463.x
Shuster, J., & Toplak, M. E. (2009). Executive and motivational inhibition: Associations
with self-report measures related to inhibition. Consciousness and Cognition, 18(2),
471-480. doi:10.1016/j.concog.2009.01.004
Smit, H., & Rogers, P. (2000). Effects of low doses of caffeine on cognitive performance,
mood and thirst in low and higher caffeine consumers. Psychopharmacology, 152(2),
167-173. doi:10.1007/s002130000506
Stuss,D.T.,Toth,J.P.,Franchi,D.,Alexander,M.P.,Tipper,S.,&Craik, F. I. M. (1999).
Dissociation of attentional processes in patients with focal frontal and posterior
lesions. Neuropsychologia, 37, 1005–1027.
Taylor, A. J. (2016). Trait Impulsivity And Oculomotor Inhibition. Studia Psychologica,
58(2), 134-144. doi:10.21909/sp.2016.02.712
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
57
Tieges, Z. (2004). Caffeine strengthens action monitoring: evidence from the errorrelated negativity. Cognitive Brain Research, 21(1), 87–93.
doi:10.1016/j.cogbraines.2004.06.001
Tieges, Z., Snel, J., Kok, A., & Ridderinkhof, K. R. (2009). Caffeine does not modulate
inhibitory control. Brain and Cognition, 69(2), 316-327.
doi:10.1016/j.bandc.2008.08.001
Tieges, Z., Snel, J., Kok, A., Wijnen, J. G., Lorist, M. M., & Ridderinkhof, K. R. (2006).
Caffeine improves anticipatory processes in task switching. Biological Psychology,
73(2), 101-113. doi:10.1016/j.biopsycho.2005.12.005
Ting, W. K., Schweizer, T. A., Topolovec-Vranic, J., & Cusimano, M. D. (2016).
Antisaccadic eye movements are correlated with corpus callosum white matter mean
diffusivity, stroop performance, and symptom burden in mild traumatic brain injury
and Concussion, Frontiers in Neurology, 6, 271. doi:10.3389/fneur.2015.00271
Vendrell, P., Junque´, C., Pujol, J., Jurado, M. A., Molet, J., & Grafman, J. (1995). The
role of prefrontal regions in the Stroop task. Neuropsychologia, 33, 341–352.
Verbruggen, F., & Logan, G. D. (2008). Response inhibition in the stop-signal paradigm.
Trends in Cognitive Sciences, 12(11), 418-424. doi:10.1016/j.tics.2008.07.005
Verbruggen, F., & Logan, G. D. (2009). Models of response inhibition in the stop-signal
and stop-change paradigms. Neuroscience & Biobehavioral Reviews, 33(5), 647-661.
doi:10.1016/j.neubiorev.2008.08.014
Verbruggen, F., Stevens, T., & Chambers, C. D. (2014). Proactive and reactive stopping
when distracted: An attentional account. Journal of Experimental Psychology:
Human Perception and Performance, 40(4), 1295-1300. doi:10.1037/a0036542
INHIBITION OF PREPOTENT RESPONSES AND CAFFEINATED ENERGY DRINKS
58
Vreeke, L. J., & Muris, P. (2012). Relations between behavioral inhibition, big five
personality factors, and anxiety disorder symptoms in non-clinical and clinically
anxious children. Child Psychiatry & Human Development, 43(6), 884-894.
doi:10.1007/s10578-012-0302-5
Wang, J., Tian, J., Wang, R., & Benson, V. (2013). Increased attentional focus modulates
eye movements in a mixed antisaccade task for younger and older adults. PLoS ONE,
8(4). doi:10.1371/journal.pone.0061566
Whiteside, S. P., & Lynam, D. R. (2001). The five factor model and impulsivity: Using a
structural model of personality to understand impulsivity. Personality and Individual
Differences, 30, 669-689. doi:10.1016/S0191-8869(00)00064-7
Wignall, N. D., & Wit, H. D. (2011). Effects of nicotine on attention and inhibitory
control in healthy nonsmokers. Experimental and Clinical Psychopharmacology,
19(3), 183-191. doi:10.1037/a0023292
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Footnotes
1
During the Antisaccade task participants have to generate an eye movement in the
opposite direction of a stimulus. For example, if the stimulus appeared to the left a person
has to look to the right.
2
During the Stroop task participants are required to say the color of the word, not what
the word says. For example, when participants see the word red printed in blue they have
say blue.
3
During the Stop Signal task participants have to respond during the “go” trials and
inhibit their responding when they see a stop signal. For example, participants press a
button for all of the trials except for the trials when they hear an auditory signal.
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Table 4
Statistical Analysis of the Differences Between the Inhibitory Condition and the Non-Inhibitory
Condition for the Prepotent Response Inhibition Tasks and the Flanker Task
Note: This table shows that there were statistically significant differences between the Prosaccade RT
and the Antisaccade RT (p<0.05), the Prosaccade percent error and the Antisaccade percent error
(p<0.05), the Stroop neutral RT and the Stroop incongruent RT (p<0.05), the Stop Signal Go RT and
the Stop Signal Stop RT (p<0.05), and the Flanker incompatible RT and the Flanker no-interfering RT
(p<0.05). There was no statistically significant difference between the Flanker incompatible percent
error and no-interfering percent error (p=0.486).
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Table 6
The Summary Table of 15 One-Way ANOVAs on the Effect of Caffeine on Each Dependent Variable in
Three Experimental Groups
Dependent Variable
Note: The table shows the results of the One Way ANOVA tests, which were used to find the differences in
inhibition performance, attention performance, impulsivity level, and the caffeine consumption among the
decaffeinated, low caffeinated and the maximum caffeinated groups. There were no significant differences among
the caffeine groups with an exception of the RVIP RT.
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Figure 1. The figure shows the mean reaction times for the RVIP attention task among three caffeine
conditions: decaffeinated, low caffeine, and maximum caffeine. Post hoc tests indicated that the
maximum caffeine group exhibited smaller reaction times compared to the decaffeinated group, which
means that participants in the maximum caffeine group performed better at the attention task
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Appendix
Personality Trait Questionnaire
DIRECTIONS: Please circle the number that best represents the extent to which you agree with each of
the following statements. Please be assured that your responses will remain confidential.
1
Rarely/Never
2
Occasionally
3
Often
4
Almost Always/Always
1
I plan tasks carefully.
1
2
3
4
2
I do things without thinking.
1
2
3
4
3
4
I make-up my mind quickly.
I am happy-go-lucky.
1
1
2
2
3
3
4
4
5
I don’t “pay attention.”
1
2
3
4
6
7
8
I have “racing” thoughts.
I plan trips well ahead of time.
I am self controlled.
1
1
1
2
2
2
3
3
3
4
4
4
9
10
11
12
I concentrate easily.
I save regularly.
I “squirm” at plays or lectures.
I am a careful thinker.
1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
13 I plan for job security.
14 I say things without thinking.
15 I like to think about complex problems.
1
1
1
2
2
2
3
3
3
4
4
4
16 I change jobs.
17 I act “on impulse.”
18 I get easily bored when solving thought problems.
1
1
1
2
2
2
3
3
3
4
4
4
19 I act on the spur of the moment.
1
2
3
4
20 I am a steady thinker.
21 I change residences.
22 I buy things on impulse.
1
1
1
2
2
2
3
3
3
4
4
4
23 I can only think about one thing at a time.
1
2
3
4
24 I change hobbies.
25 I spend or charge more than I earn.
1
1
2
2
3
3
4
4
26 I often have extraneous thoughts when thinking.
27 I am more interested in the present than the future.
1
1
2
2
3
3
4
4
28 I am restless at the theater or lectures.
29 I like puzzles.
1
1
2
2
3
3
4
4
30 I am future oriented.
1
2
3
4
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Informed Consent Form
Title:
The effect of energy drinks on cognitive functions
Researcher’s Contact Information
Kristina Karapetyan
Phone: 2243550271
Email: [email protected]
Thesis Advisor Contact Information
Naomi Wentworth
Phone: 847-735-5256
Email: [email protected]
Purpose
The purpose of this study is to investigate the effect of energy drinks on the cognitive
performance of college students.
Description
This study should take approximately one hour and 30 minutes to complete, where 45 minutes
will be a resting or homework period. In this study you will be randomly assigned to one of the
experimental conditions. In some of the experimental conditions you might be asked to consume
57 ml of an energy drink (approximately 1 small shot) therefore if you are sensitive to energy
drinks or if energy drinks are contraindicated in your case you should refuse to participate
in this study. If you are willing to and able to participate in this study you will be asked to
consume an assigned drink and then take a rest period of 45 minutes. During this rest period you
will be asked to complete two questionnaires – A Demographic/ Caffeine Consumption
questionnaire and a 30-question Personality Trait Questionnaire which may take up to 10 minutes
to complete. Your responses on these questionnaires, and all other responses during the study,
will be kept confidential. When you are done with completing the two questionnaires you will
have time to work on your homework. After 45 minutes have elapsed you will begin taking the
battery of five short cognitive tasks which will take approximately 35 minutes to complete.
During one of the tasks your eye movements will be recorded by an ISCAN corneal reflection eye
tracker and a video camera. These recordings will be kept confidential on a password-protected
computer. You can ask questions about the study at any time and at the end of the study you will
be debriefed about the study in more detail.
Risks of Participation
The only risk of participation in this study is related to the possibility of getting in an
experimental group where a commercially available energy drink that contains caffeine will be
consumed. Some possible side effects of the energy drink might include: increased heart rate,
agitation, dizziness, gastrointestinal upset, or insomnia. If you are aware that an energy drink
might have some adverse effects on you, or if you are concerned that it might, you should
decline to participate in the study. If you have never had any troubles related to energy drink
consumption, the present study should not pose any danger to you other than those of normal,
daily life.
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Benefits of Participation
The main benefit you will receive is the research process experience and hopefully contributing to
the body of knowledge in psychology.
Cost and Compensation of Participation
There is no explicit cost of participation in this study except the time spent participating.
Voluntariness
Your participation in this study is completely voluntary and your time and cooperation in this
research project is much appreciated. You can withdraw at any time without giving any reason
and without any penalties.
Confidentiality
Your informed consent document, responses to questionnaires, results on the tasks, and other
provided data will remain confidential. Each participant will receive a random number which will
be used to label all data files for further analyses. Hard copies of your materials will be stored in a
locked data file in a laboratory with limited access. All data files will be stored in password
protected files. Only the random number identifiers will appear on data files.
Concerns about the study
If you have any concerns or complaints about the way you were treated or if you have suffered
any research-related harm (physical, psychological, or social), you can contact the chair of the
Lake Forest College Human Subjects Review Committee, Dr. Todd Beer, at
[email protected] or (847) 735-5253.
Statement of Consent
I have read the information about the study and I have asked any questions to clarify relevant
details about the study which are of interest to me and I have received answers for them. I give
my written consent to participate in this study.
________________________________________________
Printed Name of Participant
________________________________________________ Date___________
Signature of Participant
_________________________________________________Date___________
Signature of person obtaining this consent
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Debriefing Sheet:
Thank you for your participation in this study. Your time and cooperation are
much appreciated. The main goal of this study is to investigate whether caffeinated
energy drinks have an effect on college students’ ability to inhibit prepotent, reflexive, or
automatic motor responses. Some of the tasks you have completed today, such as the
Antisaccade task, Stroop task, and Stop Signal task are considered to be the measures of
inhibition of prepotent responses. The Eriksen Flanker task that you have taken is
intended to measure another component of inhibition- Resistance to Distractor
Interference. Another task you’ve completed was the Rapid Visual Information
Processing task which assesses attention. Another goal of the study was to investigate
whether there is a relationship between impulsivity and the failure to inhibit prepotent
responses. The Personality Trait Questionnaire you completed was actually intended to
measure the impulsivity trait and during the data analyses it will be correlated with the
scores from other tasks. I did not reveal the exact nature of the trait because I did not
want to introduce a bias into the study. I hope this minor deception does not cause you
any negative feelings. If it does, I want to apologize and I hope you will let me know
what I can do in order to compensate for any negative feelings caused by this deception.
If you would like me to remove your data from the study, I will comply with your wish.
If you have any concerns or complaints about your treatment in this study or if
you have suffered any research-related harm (physical, psychological, or social), you can
contact the chair of the Lake Forest College Human Subjects Review Committee, Dr.
Todd Beer, at [email protected] or (847) 735-5253.
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Please contact me if you want to get the results of the study and also let me know if you
have any questions. Please contact me, Kristina Karapetyan, at the following e-mail
address [email protected]