This thesis has been approved by
The Honors Tutorial College and the Department of Communication Sciences and
Disorders
__________________________
Dr. Brooke Hallowell
Professor, Communication Sciences and
Disorders
Thesis Advisor
__________________________
Dr. Chao-Yang Lee
Honors Tutorial College, Director of Studies
Communication Sciences and Disorders
__________________________
Jeremy Webster
Dean, Honors Tutorial College
2
Using Eye Tracking to Examine the Relationship between Working Memory and
Auditory Comprehension in Persons with Aphasia
_______________________________________________
A Thesis
Presented to
The Honors Tutorial College
Ohio University
_______________________________________________
In Partial Fulfillment
of the Requirements for Graduation
from the Honors tutorial College
with the degree of
Bachelor of Science in Hearing, Speech, and Language Sciences
_______________________________________________
by
Penny Sullivan
June 2010
3
Table of Contents
Acknowledgements .............................................................................................5
Introduction .........................................................................................................6
Working Memory............................................................................................7
Past Research ....................................................................................................14
Working Memory..........................................................................................14
Silent Reading Comprehension and Working Memory ................................16
Eye-tracking and Aphasia Research .............................................................28
Purpose..............................................................................................................32
Research Questions and Hypotheses ................................................................33
Methods.............................................................................................................34
Participants ....................................................................................................34
Materials .......................................................................................................35
Verbal Working Memory Eye-Tracking Procedures ....................................37
PALPA Auditory Comprehension Procedure ...............................................44
Results ...............................................................................................................45
Correlations for the aphasia group ................................................................45
Correlations for the control group.................................................................48
Hypotheses correlations ................................................................................48
Other Correlations .........................................................................................49
4
Discussion .........................................................................................................49
References .........................................................................................................55
Appendix A: Normative Data for PALPA Subtests .........................................59
Appendix B: Comprehension tasks scores for participants with Aphasia ........60
5
Acknowledgements
This work was supported by the Honors Tutorial College Dean’s Discretionary
Fund and a grant from the National Institutes of Health. Gratitude is extended to Dr.
Brooke Hallowell, Dr. Maria Ivanova, Dr. Sabine Heuer, Dr. Vanessa Shaw, Dr.
Chao-Yang Lee, the Neurolinguistics Laboratory Team, the Stroke Comeback Center,
and the Honors Tutorial College. None of this could have been accomplished without
everyone’s help and support that I am very grateful to have throughout this entire
project.
6
Introduction
The aim of this paper is to examine eye-tracking-measures of working memory
and their relationship with auditory comprehension scores in persons with aphasia.
The definition of aphasia “is an acquired communication disorder caused by brain
damage, characterized by an impairment of language modalities: speaking, listening,
reading and writing; it is not the result of a sensory or motor deficit, a general
intellectual deficit, confusion or psychiatric disorder” (Hallowell & Chapey, 2008, p.
3). Aphasia is caused by damage to language areas of the brain. Common causes of
damage include stroke, tumors, degenerative diseases, and traumatic brain injury.
Within the diagnosis of aphasia there are subtypes based on the site of lesion
and the subsequent patient symptoms. The subtypes of aphasia can be placed into
three different categories, fluent, non-fluent, and other. In fluent aphasias the main
symptom is difficulty with language comprehension and in non-fluent aphasias the key
difficulty is with language production. The three main types of fluent aphasia are
Wernicke’s aphasia, conduction aphasia, and transcortical sensory aphasia. The
prominent symptoms of Wernicke’s aphasia are impaired auditory and reading
comprehension, but persons with Wernicke’s aphasia have fluent expressive language
abilities. The person’s expressive language is grammatically correct; however, there
can be instances of using nonsense words without awareness that the speech is
meaningless. Conduction aphasia’s trademark symptom is trouble repeating words or
sentences. One way in which conduction aphasia differs from Wernicke’s aphasia is
that persons’ with conduction aphasia have relatively better auditory comprehension.
7
Persons with transcortical sensory aphasia have fluent and articulate speech but
produce paraphasias.
The main types of non-fluent aphasias are Broca’s aphasia and transcortical
motor aphasia. Typical symptoms associated with Broca’s aphasia are difficulty
articulating words and restricted vocabulary; however, these individuals have
relatively good auditory and reading comprehension. Classic transcortical motor
aphasia features are syntactic errors, difficulty imitating, and difficulty initiating
speech and formulating responses in conversation. Finally, global aphasia is unique in
that it is a combination of fluent and non-fluent aphasias. Global aphasia is
categorized by impaired expressive and receptive language abilities. Symptoms
include a small vocabulary, few utterances, and a limited understanding of language.
Other forms of aphasia are anomic aphasia and primary progressive aphasia. Anomic
aphasia is characterized specifically by word retrieval difficulties. Individuals with
primary progressive aphasia have language skills that worsen over time. This type of
aphasia can be caused by degenerative diseases that affect the brain. Another
consequence of primary progressive aphasia is cognitive decline. While the language
skills are affected right away and continue to worsen, cognitive decline may occur
later in disease progression.
Working Memory
According to Cowan et al. (2005) working memory entails holding a small
amount of information in memory while involved in another cognitive task. There are
multiple theories of working memory that addresses how and what type of information
8
is stored. The original working memory model was presented by Baddeley and Hitch
(1974). It consisted of a central executive system with two subsystems known as slave
systems. The central executive system is the controller of the working memory, and its
primary job is processing information and storage of information coming into the
system. It is the central executive that delegates importance of information coming in
and what should be attended to first. Additionally, when new information comes into
the system, the central executive decides how to divide additional resources to process
the incoming information. The two slave systems are the visual sketchpad, which
takes in visuospatial information, and the phonological loop. The phonological loop is
important to research of working memory in aphasia because it is where verbal
information is said to be rehearsed. In the phonological loop verbal information is
encoded and rehearsed to form a memory trace. However, if the memory trace is not
rehearsed it is forgotten, and the verbal information is then lost after about two
seconds. The phonological loop is also theorized to be involved in silent reading, in
addition to processing auditory information (Wright & Shisler, 2005).
An additional theory that was based on the original Baddeley and Hitch (1974)
theory was developed by Daneman and Carpenter (1980). These authors developed the
working memory span for testing working memory. This type of testing has been
expansively used in studies examining working memory. The concept was based on
the theory that working memory is a limited resource that must be split between
processing and storage. This theory was developed by having participants read
sentences out loud and remember the final word of each sentence. As the task
9
progressed the sentences increased in length and set size (Wright & Shisler, 2005).
This type of testing is still widely used in studies to examine working memory and has
been modified to incorporate other type of modalities. For example, the concept of this
type of assessment task was used in the eye-tracking verbal working memory tasks on
which this current study is based.
Another theory of working memory was proposed by Hasher and Zack (1988).
They claim that working memory has a limited capacity because there is competition
between irrelevant and relevant information. The irrelevant information is taking up
what is known as restricted space and leaves fewer resources for processing and
storage of relevant information. Studies that continued from this theory primarily
examined working memory in older adults, and results indicated that older adults
performed worse on working memory tasks than younger adults. The researchers
attributed this not to the reduction of working memory but rather reduced ability to
weed out irrelevant information. Subsequent work from these studies continued to
focus on older individuals and their ability to ignore irrelevant information (Wright &
Shisler, 2005). This theory pertains to the current study because most persons with
aphasia are older adults. Knowing the abilities and general effects of age on working
memory is critical when determining how to test working memory in individuals with
aphasia.
In another theory of working memory, Caplan and Waters (1999) discuss that
previous theories do not take into account the specific knowledge needed for language
processing. They claim there is a distinct resource in working memory for language
10
processing, and there are two separate sub-processes within this distinct system. The
first process is unconscious comprehension of the first meaning of an utterance, and
the second process is a conscious act controlled by the person. An example of when
the second process is necessary in understanding a passive sentence, for example, the
cat was chased by the dog. The second process would be used to comprehend that the
verb to chase goes with the agent/subject (the dog) and not the object (the cat) (Wright
& Shisler, 2005). Working memory theories that specify how language processing
occurs are important to examine while developing working memory tasks, especially
when tasks entail sentence comprehension.
Due to the number of theories regarding working memory, deciding which
tasks to use in experiments is a complex decision, even when designing studies
involving unimpaired individuals. Furthermore, it can be an even bigger challenge to
determine what type of working memory task will achieve the most valid index of
working memory for an individual with aphasia.
Additionally, working memory tasks entail methodological problems when
used with persons with aphasia. Due to the language deficits common in this
population it can be difficult to assess their true working memory capabilities, since
many of these tests are highly language-based. For example, a specific test may
require a person to use spoken language or listen to an array of directions in order to
assess part of his or her working memory. However, if a person with aphasia has
deficits in either comprehension or production of language that test may not show the
person’s true working memory abilities.
11
There are many assumptions that must be made when interpreting responses as
being indicative of true comprehension. First, there is the assumption that respondents
are able to comprehend verbal directions given for a task. With many types of aphasia
the ability to understand verbal directions is impaired, and this impairment can lead to
individuals scoring poorly on working memory tasks. However their low score is due
to poor auditory comprehension, not necessarily working memory abilities. Second,
there is often an assumption that expressive language is intact. Some persons with
aphasia are unable to form utterances or to form them correctly in either repetition or
spontaneous speech. When a task requires the participant to say a word that has been
presented previously to determine if the word was held in memory, the person with
aphasia may remember the word, but may be unable to form the word due to
expressive language impairments. Third, there is an assumption that the respondent is
able to perform motor skills. This is a concern for persons with aphasia because
sometimes physical impairments are also symptoms of the brain injury that caused the
aphasia. For example, if a task requires a participant to perform a motor action, such
as pointing, the neurological impairments may prevent the person from pointing, and
will again lead to an inaccurate measurement of working memory.
Additionally, there are methodological problems for working memory tasks for
persons with aphasia. First, working memory tasks have a common lack of control for
length or complexity of words. This lack of control is a problem because as words
become longer or more complex certain persons with aphasia will have greater
difficulty recalling or comprehending words of greater length and complexity. In
12
addition, working memory evaluations rely on off-line tasks. Off-line tasks entail
recording of responses after the storage and processing components of the working
memory tasks are over. For instance, the processing component may entail reading a
set of sentences, and the storage component may entail remembering the last word of
the each sentence read. The index of working memory abilities measured would occur
after the sentences were read. This index does not directly measure what is going on
while the person is reading the sentences and remembering the final words. Eyetracking entails constant monitoring of where the person is looking during the
processing, storage, and recall. Constant monitoring can lead to a better understanding
of what is going on during the processing and storage components, and not just the
final recall task.
An additional problem with some working memory assessments is the use of
metalinguistic tasks. The term metalinguistic refers to using language to think about
language, which in and of itself is not necessarily a natural, everyday process and use
of language. An example of a metalinguistic task in working memory assessments is
asking participants yes/no questions about whether previously presented sentences
are linguistically plausible. This type of processing is not used in everyday situations.
A person with a language impairment may find this task significantly more difficult.
Overall, problems with working memory tests and tasks are not just confined to
assumptions made about what persons with aphasia are capable of doing but include
methodological flaws as well.
13
Much remains unknown about the nature of working memory and specific
impacts of working memory deficits on language comprehension in people with and
without aphasia. There is a general consensus that working memory deficits are
associated with deficits in auditory comprehension. However, much remains unknown
about the degree to which working memory plays a role in comprehension and the
specific aspects of working memory involved.
The purpose of this investigation is to examine this relationship between
working memory as indexed by an eye-tracking method and auditory comprehension.
An eye-tracking method for testing persons with aphasia may help overcome the
assumptions about abilities and problems with testing methods described earlier. The
verbal working memory eye-tracking method includes an auditory comprehension task
as the processing component, and a working memory task as the storage component.
The entire verbal working memory eye-tracking task will be described in detail in the
methods section. We will investigate the relationship between verbal working memory
eye-tracking scores and sentence and single word comprehension scores from the
Psycholinguistic Assessments of Language Processing in Aphasia (PALPA) (Kay,
Lesser, & Coltheart, 1992). In addition, we will investigate the relationship between
the aphasia quotient from the Western Aphasia Battery (WAB) (Kertesz, 2007) and
the verbal working memory eye-tracking scores.
14
Past Research
Working Memory
Caplan and Walters conducted a series of experiments that examined working
memory and reading comprehension of sentences. One study in the series looked
specifically at syntactic processing in aphasia. First, participants went through
multiple screenings to ensure that they would be able to complete all the experimental
tasks because some people with severe aphasia may not have been able to complete
them based on their language skills. The first screening task participants completed
was the repetition task. Participants repeated 20 nouns and 20 nonsense words after
the researcher presented them orally. A correct response consisted of producing the
same phonemes and stress pattern, without dysarthric or apraxic characteristics.
Apraxic characteristics consist of the inability to sequence and coordinate the motor
functions needed to produce speech. Dysarthic characteristics are troubling
coordinating the speech mechanisms due to paralysis or weakness of the muscles
controlling the speech mechanism. If the participant achieved 75% or better accuracy,
he or she progressed to the next phase. The second screening was a sentence
comprehension task. The task was in the form of sentence picture matching, and the
participants needed to use their pragmatic knowledge to understand the sentences. In
total there were 15 active sentences and 5 passive sentences. Each sentence was
accompanied by two pictures, one target image that matched the auditory stimulus and
one foil image, and the participant had to choose the correct picture. The participants
who achieved 80% or better accuracy progressed to the next phase of the study. The
15
last participant selection task consisted of participants who performed between 6590% on the second screening. These individuals were given a more syntactically
complex word-picture matching task. Some examples of the syntactically complex
sentences types were passive, object relative, and cleft object sentences. Again,
participants who scored between 65-90% progressed to the experiment phase. Ten
participants met the criteria for the study, two males and eight females. Their average
age was 66.6 years old (Caplan & Walter, 1999).
The first task in the experimental procedure was the digit span task.
Participants remembered a sequence of numbers that were between 1 and 9. The digit
span for each participant was the level at which participants correctly recalled the
sequence six out of ten times. The task was discontinued when the participant was able
to recall the sequence three or fewer times out of ten. Once the digit span was found
for each participant, the working memory task was given (Caplan & Walter, 1999).
The working memory task consisted of the same picture sentence matching
task that was used in the screening. In addition to sentence picture matching,
participants were required to remember a digit sequence including one less digit than
their previously determined digit span. First, participants were read a digit sequence
that they were required to repeat aloud continuously. When the participant repeated
the sequence correctly the researcher showed the two pictures (one target and one foil)
and read the auditory stimulus. The participants were required to point to the picture
that matched the verbal stimulus and repeat the sequence of digits after picking a
16
picture one last time. The accuracy of the last sequence of digits stated and the picture
chosen were both recorded as measures of working memory (Caplan & Walter, 1999).
Results from this study showed that there was no reduction in syntactic
processing ability while participants completed the digit span task. These results were
compared with previous findings about participants without cognitive impairments and
also participants who had Alzheimer’s disease. Due to the fact that syntactic
processing resources remained stable, the researchers suggested that their findings
provide evidence that syntactic working memory is distinct from other aspects of
working memory (Caplan & Walter, 1996). This is an important finding for evaluating
the relationship between working memory and auditory sentence comprehension
because it is important to examine what working memory tasks are actually indexing,
and how this relates to language processing.
Silent Reading Comprehension and Working Memory
Research conducted prior to auditory sentence comprehension and working
memory started with the relationship between silent reading comprehension and
working memory. Caspari, Parkinson, LaPointe, and Katz (1998) investigated working
memory in persons with aphasia and how it related to reading comprehension. The
two aims of the study were to find differences in the working memory capacity of
persons with aphasia and examine if a relationship exists between reading or listening
span working memory tasks and silent reading comprehension. The study consisted of
23 participants with aphasia due to a cerebrovascular accident to the left hemisphere.
17
The age ranges of participants were 35-85 and these participants were at least six
months post- stroke.
The Western Aphasia Battery (WAB) was utilized to assess language
performance (Kertesz, 2007). The subtests given were spontaneous speech, auditory
comprehension, repetition, and naming. These four subtest scores combined were used
to determine the aphasia quotient, the number researchers wanted to use in the
correlation analysis. The aphasia quotient was also used to classify participants as
either mild or severe. Fluency was determined for each participant by the score from
the spontaneous speech subtest. Six participants were classified as non-fluent and were
excluded from the study due to lack of usable speech.
Silent reading was assessed using the Reading Comprehension Battery for
Aphasia (RCBA) (LaPointe & Horner, 1979). The RCBA consists of silent reading
comprehension at the word, sentence, and paragraph level. Researchers based their
study on a previous study by Daneman and Carpenter (1980); however, they needed to
modify the task for persons with aphasia (Caspari et al., 1998).
In the original task, participants read a number of sentences and had to
remember the last word of each sentence. Participants were instructed to recall all the
words from memory and were not given a word bank. In addition, participants were
not allowed to say the last word of the last sentence in the set first. The first
modification of this task was that the recalled word was not the last word of the
sentence but rather a separate word from the sentence. This modification was included
because separating the word from the sentence gave researchers more control on
18
length and complexity of sentences. In addition, this modification gave investigators
the freedom to choose the target word without requiring the word to make sense in the
context of the sentence. The second modification was specifically implemented for the
participants with aphasia. In the original design the sentence length was between 1316 words, and researchers shortened the sentence length to 5-6 words. Researchers
revised the sentence length because it is difficult for persons with aphasia to
understand long and grammatically complex sentences. In addition to shortening
sentences, the sentences used were simple, declarative sentences. A third modification
was the selection of the target words. Researchers chose high frequency words—
those commonly used in everyday life— and words that were easy to visualize. The
final modification was a change in response modality from free recall to recognition of
the words to be remembered. This recognition was done using picture representations
of the words to be remembered with foil images around it. The foil images were
selected randomly from a list of words that were similar to the word in frequency and
ability to be visualized (Caspari et al., 1998).
Participants took part in two working memory tasks, a listening version and a
reading version. There were 22 participants in the listening task and 14 in the reading
task. The listening span task required participants to listen to sentences and remember
the final word after the sentence was completed. Participants were presented the
sentence and the word to be remembered on a white index card, which was read to the
participant by the examiner. Immediately following the reading of the card, a new card
was placed on top of the original. The new card indicated the word to be remembered
19
from the previous card. Once the participant indicated which picture was the word to
be remembered a trial was complete. Once the first trial was complete, the researcher
repeated the task four more times for a total of five trials per level. If the participant
correctly identified three of the five words to be remembered, he or she advanced to
the next level. Level two procedures were identical to level one; however, instead of
completing the recognition task after every sentence, participants completed it after
every two sentences, thus increasing the words to be remembered to two words. There
were a total of six levels. At the last level participants were instructed to recognize six
words. Once the recognition task was complete; participants were asked questions
about the sentences that were read aloud. The sentences were either yes/no questions
or were predetermined comprehension questions about the sentences. The reading
span task followed the same procedures as the listening span task, except that
participants read the cards themselves. Participants were required to read the sentence
out loud to prevent them from just focusing on the final word to be remembered
(Caspari et al., 1998).
Scoring for both the listening span and the reading span tasks was determined
by the level the participant reached, known as the level score. If a participant was able
to correctly complete the recognition task in three of the five trials that level was
considered successful. Partial credit was given to participants who were able to
correctly complete two of the five recognition trials. Also the number of correct words
was recorded for each participant (Caspari et al., 1998).
20
Researchers determined the average score of the correct content questions for
each participant. The average score on the content questions was 87% accuracy,
indicating the sentences were processed by the participants. Pearson correlations were
used to determine if any relationships emerged amongst the variables. There was a
significant relationship among listening span scores, RCBA scores, and the WAB
aphasia quotient. In addition there were significant relationships among the reading
span task, RCBA scores, and the WAB aphasia quotient. Researchers also ran a
correlation analysis on each subtest of the RCBA and listening span task, and found
significant relationships among all the subtests except one, the word/auditory subtest
(Caspari et al., 1998).
The researchers interpreted the correlations to indicate that working memory
capacities and silent reading comprehension are related in persons with aphasia. In
addition, they concluded that oral language does have a relationship with working
memory as well, based on the correlations with the WAB for both the listening span
and the reading span tasks. Also based on the correlations between the listening span
task and the morphosyntax subtest of the RCBA the authors concluded that persons
with aphasia with reduced working memory abilities had impaired performance on
more complex sentence types (Caspari et al., 1998).
Auditory Sentence Comprehension and Working Memory
Friedmann and Gvian (2003) compared working memory and auditory
sentence comprehension in persons with aphasia whose native tongue was Hebrew to
a control group of native Hebrew speakers who did not have any neurological
21
impairments. They evaluated participants’ working memory abilities through five
different tasks. The first task was a digit span task in which participants were orally
presented a random series of numbers from 1-9 ranging in sets from two to nine digits
increasing in difficulty with each progressive level. The first level of eight started with
two digits and each level increased by 1 digit. Each participant’s digit span was
defined as the level at which he or she was able to recite the series correctly in three of
seven trials. The second and third tasks were the word span task and the non-word
span task, respectively, and both tasks had the same protocol. The stimulus was
presented orally and consisted of six levels ranging from two to seven words
depending on the level. The word and non-word spans were determined when the
participant correctly recalled the list of words three out of five times. The fourth
working memory task was the listening span task, which was adapted from English to
Hebrew for this study. Participants were orally presented lists of sentences, ranging
from two to six sentences per level. Incorporated target sentences were controlled for
length, number of syllables, word frequency, and the amount of correct or incorrect
sentences per level. The task required participants to determine if the sentences were
true or false and to remember the final word of each sentence. The listening span task
differed from the word and non-word span tasks, in that it utilized a recognition task
instead of the free recall task. Participants were shown pictures and recognized the
words at the end of sentences that they heard. However, the criterion to advance to the
next level was the same, requiring participants to correctly recognize the final words
in three out of five sets of sentences.
22
The next working memory task was the recognition task. The words from the
listening span tasks were used; however, there were no sentences presented before the
words. Participants were expected to recognize the words from a list with foils. The
final task was the n-back task. In this task participants had to judge whether the item
they heard was the same as or different than the previously presented item. There were
a total of 99 items and three different lists. The three lists were digits, short animal
names, and long animal names. Each list was presented twice, first one second apart
and then three seconds apart (Friedmann & Gvian, 2003).
The results of the control group yielded an average digit span of 7.25. Maximal
scores for the listening span task (score of 6) were achieved, and the 2-back task
results were at ceiling values. Performance on the word span tasks had phonological
similarity effects. Participants performed significantly better for phonologically
dissimilar words compared to phonologically similar words. In addition, participants
performed significantly better on shorter words than longer words. Finally,
participants remembered words significantly better than non-words (Friedmann &
Gvian, 2003).
The group of participants with aphasia was split into two groups based on
aphasia type, conduction or agrammatic. The conduction aphasia group had limited
recall and recognition in the digit, word, and non-word tasks. Performance was mixed
on the listening span task. Some participants performed at ceiling levels and others
had a limited performance. The group with agrammatic aphasia had difficulty
performing the recall portions of the digit, word, and non-word span tasks, but not the
23
recognition aspects of the other tasks. Ceiling effects were found in this group on the
listening span task and they also performed well on the n-back tasks (Friedmann &
Gvian, 2003).
After completion of the working memory tasks the participants completed two
experiments incorporating auditory sentence comprehension. The first experiment
investigated the relationship between the gap-antecedent distance and working
memory. Gap-antecedent distance refers to the number of words between the subject
and the verb. The format was sentence picture matching with two pictures, one target
image and one foil image. There was a training trial before the task began to confirm
that participants were able to identify the pictures that matched the main subjects of
the sentences. This portion consisted of 160 relative clauses that were semantically
reversible. Semantically reversible sentences are sentences in which both the subject
and the object of the sentence could realistically perform the action word (verb). The
sentence, “The dog chased the cat.” is one such example. This sentence would still
make sense if the cat chased the dog. An example of a semantically irreversible
sentence is, “The man chewed the gum.” In this instance the gum cannot chew the
man, and roles could not be reversed for the sentence to make sense. Through the
clauses, the gap-antecedent distance was varied between 2, 5, 7, and 9 word distances.
The gap increase was manipulated by the use of prepositional phrases and placement
of adjectives before nouns (Friedmann & Gvian, 2003).
The control group performed well on all types of sentences. The gapantecedent distance had no effect on how well the control participants understood the
24
sentences. The group with agrammatic aphasia performed better on subject relative
sentences compared to the object relative sentences. The group with conduction
aphasia performed well on all sentences types with no differences between different
sentence types. Even though the group with conduction aphasia had difficulty with
object relative sentences, neither group was affected by the gap-antecedent distance.
Researchers speculated that these results were based on the fact that the distance was
based on phonological units, not semantic units, which add meaningful information to
the main point of the sentence. These conclusions led to the final experiment
(Friedmann & Gvian, 2003).
In the last experiment the authors examined the gap-antecedent distance;
however, this time the sentences included an ambiguous word. Due to the position of
the ambiguous word, the gap-antecedent distance required participants to remember
information from the first part of the sentence to decode the ambiguous word, thus
forcing them to reactivate previous knowledge from the sentence. Half of the
sentences had a gap of two to three words, and half of the sentences had a gap of seven
to nine words. There were a total of 100 sentences that were presented orally.
Participants were instructed to judge if the sentence was plausible and to paraphrase
the sentence to the best of their abilities (Friedmann & Gvian, 2003).
Again, the control participant performed very well on both types of sentences.
The group with conduction aphasia performed poorly on the sentences in which the
gap-antecedent distance was larger. An interesting finding was that when the same
ambiguous word was used in the shorter gap-antecedent distance, participants were
25
more likely to understand the sentence. This difference in comprehension of sentence
types was statistically significant. The participants with agrammatic aphasia
performed at chance level for both short and long gap-antecedent distance, and there
was no significant difference between performance on the short and long gapantecedent distance (Friedmann & Gvian, 2003).
The results from experiment 1 do not support the theories that working
memory is one single entity; instead it has distinct parts for language processing. This
theory is based on the findings that even with deficits of working memory, persons
with aphasia were still able to comprehend relative clauses, even with large gapantecedent distance. Results from the second experiment supported the idea that
working memory limitations can lead to comprehension difficulties, especially with a
large gap-antecedent distance. Researchers attributed poorer comprehension to the
inability of some participants with aphasia to reactivate the main information heard in
the first part of the sentence when the sentences contained an ambiguous word
(Friedmann & Gvian, 2003).
More recently Wright, Downey, Gravier, Love, and Shapiro (2007) examined
working memory capacities for processing specific types of linguistic information and
the relationship between participants’ working memory scores and auditory
comprehension scores. They used n-back tasks in three areas: phonology, semantics,
and syntax. They found n-back tasks were suitable for calculating working memory
abilities. N-back tasks require participants to examine a set of stimuli and after a
predetermined number of trials they are expected to recognize what they have seen
26
before. For example, during the 1-back task they used four blocks; the first block
consisted of 10 items and two targets, the second block had 12 items and three targets,
the third block had 32 items and 10 targets, and the fourth block had 33 items and 10
targets. These tests require different cognitive processes including storing information
in working memory and continuously adding to it as the task continues. In addition,
participants were given the Subject-relative, Object relative, Active, Passive Test of
Syntactic Complexity (SOAP) (Love & Oster, 2002) to evaluate auditory
comprehension for syntactic structures. This test has been validated to measure
different comprehension abilities in persons who have brain trauma and it also can
identify different subgroups of aphasia. The subgroups that the SOAP identifies are
based on auditory comprehension scores. Researchers determined classification of
aphasia severity, mild or severe, based on auditory comprehension scores. They found
that the results of the syntax n-back task had a significant relationship with SOAP
non-canonical sentences, or sentences that do not follow the subject-verb-object
format (Love & Oster, 2002). Building upon to past research, the authors concluded
that linguistic-specific working memory deficits affect comprehension of the SOAP’s
non-canonical sentences (Love & Oster, 2002). No other information was given about
working memory performance with the other types of sentences from the SOAP
(Wright et al., 2007).
Sung et al. (2009) looked specifically at how working memory and sentence
comprehension are related in persons with aphasia. The first step of their research was
to separate the group of 20 persons with aphasia into high and low working memory
27
groups. The instrument for measuring working memory was a listening version of the
sentence span task. During this task, participants had to simultaneously process and
maintain linguistic information. As the task progressed the number of sentences in
which information was maintained increased. The task had 42 sentences grouped
according to the number of sentences that the participant was required to maintain
(two to five). In the working memory task, participants read each sentence and decided
if it was true or false and then also asked to remember the last word in each sentence.
To measure sentence comprehension the authors used the Computerized
Revised Token Test (CRTT) (Sung et al., 2009), which was an adaptation of the
original Revised Token Test (RTT) (McNeil & Prescott, 1978). In the original RTT
there are 10 subtests with 10 commands per subtest. The initial commands are initially
simple for example “Touch the red circle,” and then increase in syntactic complexity
as the subtests progress. In the CRTT, instead of touching actual objects, the objects
appeared on a touch screen with the same foils found in the original RTT. Participants
completed four different versions of the CRTT, three in which the commands were
presented graphically on the computer screen and one condition in which commands
were presented orally. Results indicated a significant relationship between working
memory and the CRTT auditory condition. Furthermore, working memory scores
significantly predicted the comprehension scores. The working memory scores were
also the biggest contributor to CRTT auditory comprehension scores. Even after
controlling for language severity, the relationship between working memory and the
CRTT auditory component remained significant (Sung, McNeil, Pratt, Walsh, Hula,
28
Szuminsky, et al., 2009). In another study of working memory and auditory
comprehension, Grossman and Moore (2005) studied persons with progressive nonfluent aphasia and semantic dementia. They found that deficits in grammatical
comprehension were partly related to deficits in working memory in persons with
aphasia.
Through past studies researchers have concluded that deficits in working
memory contribute to deficits in word and sentence comprehension. Prior to Ivanova
and Hallowell (2011), there were no published studies entailing the use of eye-tracking
measures of working memory. In the current investigation, we examined the
relationship between the scores obtained from a new eye-tracking working memory
method based on Ivanova and Hallowell (2011) and the relationship between scores on
word and sentence compression tests from the PALPA for people with and without
aphasia. We also examined whether there are significant relationships between the
eye-tracking verbal working memory scores and the WAB, replicating the analysis
from Ivanova and Hallowell (2011). Finally, an additional analysis will be performed
to examine the relationship between the verbal working memory eye-tracking scores
and the Multiple Choice Test of Auditory Comprehension for aphasia (MCTAC)
(Hallowell, 2011) scores. The MCTAC procedure is explained in the methods section.
Eye-tracking and Aphasia Research
Hallowell, Wertz, and Kruse (2002) developed and validated an eye-tracking
version of the Revised Token Test (RTT) (McNeil & Prescott, 1978) based on
performance of participants without neurological impairments. They administered
29
three tests, the traditional Revised Token Test (RTT), a multiple-choice pointing
version presented on a printed test manual, and a computer presented eye-tracking
version. The multiple-choice version and eye-tracking versions were set up in a
multiple-choice format. A verbal stimulus was presented to the participant along with
a set of four pictures, one target and three foil images. They measured comprehension
in the eye-tracking version by recording the proportion of the total viewing time that
participants fixated on the target image. They found that scores from the pointing
version correlated significantly with the original RTT. In addition, in the eye-tracking
version, participants looked significantly longer at the target image than the foil
images across trials and subtests.
Ivanova and Hallowell (2011) developed and validated an eye-tracking method
for measuring working memory in persons with and without aphasia. The procedure
included a traditional listening span task, a modified version of the listening span task,
a counting span task, and an eye-tracking verbal working memory task. In the
traditional listening span task participants were asked to listen to a sentence and judge
whether it was semantically plausible. Then they were asked to remember separate
words from the sentences to be recalled later in the order presented. In the modified
listening span task, the participants listened to sentences and had to remember words
to be recognized later. The task varied in difficulty because sentences varied in length
and complexity. A novel aspect of this task were the processing components.
Participants were shown four pictures, a target that matched the verbal stimulus, and
three nontarget foils. They were instructed to point to the picture that matched a pre-
30
recorded sentence. In the counting span task, participants were shown pictures with
different geometrical shapes and counted the number of specific geometrical shapes.
Participants were asked to remember the final tally of geometrical shapes for later
recall. In the eye-tracking working memory task participants were instructed simply to
look at the displays.
The comprehension task consisted of pre-recorded verbal stimuli and four
pictures in a visual array, with one target matching the verbal stimulus and three
nontarget foil images. There were a total of 25 trials in the modified listening span
task. The recall component of the working memory task was presented before each
verbal stimulus. The recall component consisted of a geometric shape that would
appear on the screen and participants were instructed to remember the shape for one
trial of the eye-tracking working memory task. For example, the participant would
first see the display of four pictures in each quadrant and hear the verbal stimulus
matching the one target image. The next display was one shape the participant needed
to remember. The third display was a second auditory comprehension task, presented
in the same format as the first screen, but containing new pictures and a new verbal
stimulus. The fourth display had one shape that also needed to be remembered.
Immediately following the fourth display of the one shape to be remembered, a fifth
display would appear with the two shapes in one corner shown in previous displays
that the participant was to remember in one quadrant and three pairs of nontarget foil
images in the other three quadrants. A set of five displays in order constituted one
trial of the eye-tracking working memory task. For example, the set size was two
31
because the task required the participant to remember two shapes. As the task
progressed the set sizes increased by one display and on shape to be remembered. For
example, in a set size of three the task was presented in the same manner with an
additional auditory comprehension task and shape to remember. The set sizes
increased up to six (Ivanova & Hallowell, 2011).
As participants looked at the displays, the researchers measured the working
memory abilities in the participants, with and without aphasia, by examining the
proportion of total fixation duration on the target image. First, researchers defined
fixation time as a stable eye position for at least 100 milliseconds with an accepted
range of four pixels horizontal and six pixels vertical. Once fixation time was defined,
researchers used the proportion of fixation duration on the target image to determine if
the participants understood the verbal stimulus in the processing task and if they
recalled all the shapes from the storage tasks. Proportion of fixation time is defined as
the total fixation duration on the target image divided by the total fixation duration on
the entire screen. The proportion is examined to determine how much of the total
fixation times are spent on the target image. Based on previous findings, if
participants’ total fixation duration times exceed chance levels it is concluded that the
participant comprehended the verbal stimulus or recalled all the shapes from the
storage task (Hallowell et. al., 2002).
Ivanova and Hallowell (2011) found a significant correlation between
traditional listening span and modified listening span scores. This validated the
method for indexing working memory. Scores from the counting task correlated
32
significantly with the modified listening span task scores. These scores also showed
significant correlation with the verbal working memory eye-tracking scores. This
indicates that the eye-tracking was a reliable measure of verbal working memory.
Finally, a correlation analysis was performed on the auditory comprehension
scores from the WAB (Kertesz, 2007) and the eye tracking working memory scores
for the participants with aphasia. There was no significant correlation between the
scores. A possible reason for this is the WAB does not include detailed auditory
comprehension tasks.
Purpose
The purpose of the current study was to build upon a previous finding by
Ivanova and Hallowell (2011) that there was no correlation between verbal working
memory scores and auditory comprehension scores from the WAB (Kertesz, 2007).
We built upon this finding by using alternative indices for measuring auditory
comprehension of spoken words and sentences. The indices used were subtest 47 and
subtest 55 of the Psycholinguistic Assessments of Language Processing in Aphasia
(PALPA) which assess single word and sentence comprehension, respectively (Kay &
Terry, 2004). The PALPA is a comprehensive test used widely in aphasia research
studies across a wide range of aphasia types. It has a number of subtests designed to
test specific aspects of language processing in a persons with aphasia (Kay, Lesser, &
Coltheart, 1992). This feature is suitable for this study since the goal is to examine
how word and sentence comprehension scores relate to working memory scores, as
indexed via the novel method of eye-tracking. We also used an additional auditory
33
comprehension index, the MCTAC (Hallowell, 2011), for an additional idex of
participants’ working memory abilities. We will examine whether a correlation exists
between verbal working memory eye-tracking task results and the scores from the
word and sentence comprehension subtests.
Research Questions and Hypotheses
We will first replicate the results from Ivanova and Hallowell (2011) by
examining the relationship between the WAB aphasia quotient and the WAB auditory
comprehension subtest scores and the scores from a revised verbal working memory
eye-tracking task.
Hypothesis 1: As found by Ivanova and Hallowell (2010) we expect there will
be no significant correlation between eye-tracking verbal working memory scores
indexed by proportion of fixation duration on target and the scores of the WAB
aphasia quotient and the WAB auditory comprehension scores.
Hypothesis 2: We expect that there will not be a significant relationship
between eye-tracking verbal working memory scores, as measured by the proportion
of fixation duration on the target, and the scores from subtest 55 of the PALPA, which
measures auditory sentence comprehension. Even though subtest 55 of the PALPA is a
more detailed auditory comprehension test at the sentence level than the WAB
auditory comprehension, we believe this relationship will not be significant. The
previous finding supports the claim that there is not a relationship between verbal
working memory scores and auditory comprehension.
34
Hypothesis 3: We expect there will be no significant relationship between eyetracking verbal working memory scores as indexed by the proportion of fixation
duration on target and the scores from subtest 47 of the PALPA, which measures
spoken word comprehension. This task was included because of the chance that some
participants with aphasia would be unable to complete the subtest 55 due to the
severity of their aphasia. It is beneficial to our study to have at least one test other than
the WAB to test auditory comprehension, in case such an event occurred.
Hypothesis 4: We expect there will be no significant relationship between eyetracking verbal working memory scores as indexed by the proportion of fixation
duration on target and the scores from the MCTAC. We believe there will not be a
relationship based on preivous findings.
Methods
Participants
All participants in the study were native speakers of English between the ages
of 21-89 years old and had normal-to-corrected vision and hearing. There were 28
participants with aphasia and 40 participants without aphasia. The mean ages of the
aphasia group and control group were 58.8 years (range: 24-88 years; standard
deviation: 14.9) and 54.4 years (range: 24-85 years; standard deviation: 20.2)
respectively. The groups did not differ significantly by age (t(66)=-0.996, p=0.32) or
education (t(66)=-0.166, p=0.87).The control participants had no history of speech,
language, or neurological impairments. The aphasia group members had a diagnosis of
aphasia confirmed by a speech language pathologist who was not involved in the
35
study. Only those with aphasia as a result of a stroke were included and they were
required to be at least two-months post-onset.
The vision and hearing screenings were administered prior to the study. This
entailed a detailed vision screening to ensure adequate eye health in order to complete
the eye-tracking calibration. The vision screening consisted of checking the
participant’s field of vision for visual cuts, near vision, ocular movement, pupil
reaction, and color vision. The hearing screening tested participants at 500, 1000, and
2000 Hz at 30 dB SPL. This decibel level was used because 30 dB SPL is lower than
typical conversation level and would be a conservative estimate of the level needed to
hear the verbal stimuli.
Materials
Prior to the eye-tracking experiment, control participants completed a
cognitive screening using the Mini Mental State Examination (MMSE) (Folstein,
Folstein, & McHugh, 1975). The MMSE is a relatively short screening tool for
cognitive impairments. This is important to include because having cognitive and/or
neurological impairments are exclusion criterion for control participants. The language
skills of the participants with aphasia were assessed using the WAB (Kertesz, 2007).
The sections of the WAB utilized were commands, yes/no questions, word
recognition, auditory comprehension, and aphasia quotient. The WAB was used
because this was the original index used to assess auditory comprehension in the study
conducted by Ivanova & Hallowell (2011).
36
After reviewing multiple test batteries for persons with aphasia that assess
spoken language, it was decided the PALPA was the best choice. The PALPA is a
comprehensive test for assessing people with aphasia. It has many subtests that allow
one to test highly specific aspects of the abilities of a person with aphasia (Kay,
Lesser., & Coltheart, 1992). This feature suits our study as we want to examine how
word and sentence comprehension scores relate to working memory scores, as indexed
via an eye-tracking method. Subtest 47 of the PALPA was developed to assess
auditory comprehension of spoken words and Subtest 55 of the PALPA indexes
auditory sentence comprehension (Kay, Lesser, & Coltheart, 1992). Subtest 55 has 14
different sentence types, with at least two sentence trials within each sentence type.
The large number of sentence types allows for a wide range in sentence difficulty
(Kay, Lesser, & Coltheart, 1992). This enables researchers to detect the participant’s
comprehension level in both easy and challenging sentence types.
The PALPA has been used in a large number of research studies. In 2004, Kay
and Terry did a ten-year review of research studies that utilized the PALPA since the
test was released. They found that 218 articles cited the use of the PALPA over the
first ten years of its publication and this number has increased steadily over the ten
years since it was published (Kay & Terry, 2004). In addition, the increase was
comparable to two other aphasia test batteries: the Birmingham Object Recognition
Battery (Riddoch & Patterson, 1992) and the Pyramids and Palm Trees Test (Howard
and Humphreys, 1993). Kay & Terry (2004) also found the PALPA was used to
assess participants with a range of aphasia types, based on the site of lesion. The fact
37
that this test can be used for a wide range of aphasia types is beneficial for this study
because we are not identifying what specific type of lesion or aphasia each participant
has. One interesting aspect of the study was the data regarding the exact number of
times each one of the 60 subtests was used. Subtest 47, word picture matching, was
cited 89 times, more than any other subtest. Subtest 55, sentence picture matching,
was cited 10 times, which represented the median of the list (Kay & Terry, 2004).
Overall, the PALPA subtests are a great match to what we are investigating, and they
have been proven to be reliable tools in previous research.
The final language comprehension task used was the pointing version of the
MCTAC (Hallowell, 2011). The MCTAC was originally based on the verbal stimuli in
the Revised Token Test that was described earlier (McNeil & Prescott, 1978). The
MCTAC contains eight subtests with five trials per subtest. The format of this task is
word/sentence picture matching. An example of the first subtest auditory stimulus is
“Red Square”, and the participant looks at the display which has 4 pictures: 1
matching the auditory stimulus (red square) and three foil images. As the subtests
progress the auditory stimulus becomes more challenging. Difficulty is accomplished
via the use of two shapes together (red square and blue circle), small and large shapes
(big black circle), directions (the red square is in front of the blue square), use of left
and right (the white circle is to the left of green square), and combining the directions
and the small and large shapes (the little blue square is to left of the big black circle).
Verbal Working Memory Eye-Tracking Procedures
38
The verbal working memory eye-tracking task was modeled after the previous
study by Ivanova and Hallowell (2011). The eye-tracking system used was the Eye
Gaze Edge. The system consisted of a 17- inch computer monitor used to show the
displays. At the base of the screen was a camera that takes 60 pictures per second to
determine eye movements. The camera takes pictures of where the eye is fixating, by
use of an infrared light that is in the center of the camera lens. The infrared light
emitting diode (ILED) shines into the eye and causes two points of reflection. The first
point of reflection is on the cornea and the other is on the pupil. The eye-tracking
system calculates where the person is looking based on the position of the center of the
pupil and the reflection of the cornea. Refer to Figure 1 for a pictorial representation
of the Eye Gaze Edge system (LC Technologies, Inc., 2009)
39
An important aspect of the Eye Gaze Edge system is the calibration process.
First, researchers adjusted the camera so the light was reflected from the pupil. There
is a box at the top right of the display showing the picture of the eye while it is being
calibrated. When the center of the pupil turns white in the box, the camera is in the
correct position. Next, the participant completed the 15-second calibration process in
which he or she used his or her eyes to follow a dot moving around the screen to each
of nine key points (LC Technologies Inc., 2009). Once the participant correctly
followed the dots, the researchers were able to start the verbal working memory task.
A chin rest was utilized to assist in keeping participants’ heads steady during the
calibration process. Keeping participants’ heads steady was important because even a
slight movement of the head can cause the eye tracking system to lose calibration
accuracy.
Two examiners conducted the eye-tracking experiment. One examiner
operated the computer files to bring up the verbal working memory tasks and provided
instructions to the participants. The other examiner tracked where the participant was
looking on a separate monitor that faced away from the participant and noted whether
the person’s eye movements remained calibrated and if they correctly completed the
training trials. Participants completed two training modules that preceded the
experimental task. The first training module incorporated color recall, and served as
the working memory task. The second training module involved the dual task of color
recall and auditory sentence comprehension.
40
In the first training module the examiner instructed the participant to look at
the color on the computer screen and remember it. Following the first display a new
display appeared with a different color, and the examiner instructed the participant to
remember the color. The next display was the color recall test display, which had four
sets of two colors in the four corners of the screen (one target pair and three foil pairs
of colors) The participant was instructed to look at the corner with the two colors he or
she had just seen. Refer to Figure 2 for the pictorial representation of the color recall
task. Participants who successfully recalled two consecutive color recall test displays
advanced to the dual verbal working memory training task. If the participant could not
correctly complete the color recall training module, he or she did not participate
further in the study.
41
42
The dual task consisted of auditory sentence comprehension and color recall.
Participants were instructed to listen to words, look at pictures and remember colors.
In the auditory comprehension portion of the dual task, a verbal stimulus was
simultaneously presented with four images that appeared in the four corners of the
screen, one target image that matched the verbal stimulus and three foil images. The
next screen displayed a color, and the examiner instructed the participant to remember
the color. The sequence of auditory comprehension and color recall repeated again
followed by a color recall test display (see Figure 3). There were a total of seven
training trials. Training trials one through five comprised two-color recall displays.
Trial six included a three-color recall display, and trial seven included a four-color
recall test display. Participants had to successfully remember two consecutive twocolor recall test displays before advancing beyond trial five which included more than
two colors to recall.
43
44
The procedures for the experimental task were identical to those in the dual
training task. The instructions given to the participant before the experiment began
were “Everything will be just like we practiced. Listen to the words and look at the
pictures. Remember the colors that you see. Then look at the corner with the colors
you just saw. Listening to the words and remembering the colors you see are equally
important. You do not need to point or say anything.” The first three trials in the
experimental task started with participants recalling two colors. At the completion of
every three trials, the number of colors to recall increased by one, up to six colors.
During the experimental trials the examiner watched the monitor of where the
participant was looking to ensure the participant was calibrated on the eye-tracker for
the duration of the experimental task. Once the verbal working memory eye-tracking
task was complete, the participants’ PALPA subsets were administered.
PALPA Auditory Comprehension Procedure
PALPA subtests 47 and 55 were used to assess single word and sentence
comprehension, respectively. The format of subtest 47 was word-picture matching.
The examiner verbally presented a word and instructed the participant to point to the
picture that best matched the spoken word among five choices that included a target
picture and four foil images. The format of subtest 55 was sentence-picture matching.
Subtest 55 included 14 different sentence types, with at least two sentences per type.
The test entailed a wide range in sentence difficulty and enabled the examiner to
detect the comprehension level of the participant and performance across the 14
sentence types. The examiner read a sentence out loud and the participant selected the
45
picture out of a field of three that best matched the spoken sentence. The examiner
marked which picture the participant chose and after the session was over calculated
the number of correct answers. See Appendix A for PALPA subtest normative data.
Results
Pearson’s correlations were calculated with the language assessment data.
Correlations were estimated for the aphasia group, which can be found in Table 1, and
the control group, which can be found in Table 2.
Correlations for the aphasia group
There was a significant correlation between performance on the MCTAC and
gender (r = -0.553, n = 27, p= 0.003), the aphasia quotient (r = 0.710, n = 27, p =
<0.001), performance on PALPA subtest 47 (r = 0.387, n = 26, p = 0.051),
performance on PALPA subtest 55 (r = 0.780, n = 25, p = <0.001), performance on
WAB commands (r = 0.660, n = 27, p = <0.001), the WAB comprehension total (r =
0.717, n = 27, p = <0.001), and performance on the WAB word recognition (r = 0.752,
n = 27, p = <0.001).
Performance on PALPA subtest 55 was significantly correlated with the
aphasia quotient (r = 0.765, n = 25, p = <0.001), gender (r = -0.515, n = 25, p =
0.008), performance on PALPA subtest 47 (r = 0.558, n = 25, p = 0.004), performance
on the WAB commands (r = 0.808, n = 25, p = <0.001), the WAB comprehension
total (r = 0.819, n = 25, p = <0.001), and performance on the WAB word recognition
(r = 0.679, n = 25, p = <0.001).
46
There was a significant correlation between performance on PALPA subtest 47
and the aphasia quotient (r = 0.466, n = 26, p = 0.017), performance on the WAB
commands (r = 0.521, n = 26, p = 0.006), the WAB comprehension total (r = 0.515, n
= 26, p = 0.007), and performance on the WAB word recognition (r = 0.437, n = 26, p
= 0.026).
Performance on the WAB commands were significantly correlated with age (r
= -0.391, n = 27, p = 0.044), the aphasia quotient (r = 0.547, n = 27, p = 0.003), the
WAB comprehension total (r = 0.977, n = 27, p = <0.001), performance on the WAB
word recognition (r = 0.571, n = 27, p = 0.002), and performance on the WAB yes/no
section (r = 0.490, n = 27, p = 0.009).
There was a significant correlation between WAB comprehension total score
and the aphasia quotient (r = 0.610, n = 27, p = 0.001), gender (r = -0.422, n = 27, p =
0.028), performance on the WAB word recognition (r = 0.691, n = 27, p = <0.001),
and performance on the WAB yes/no section (r = 0.581, n = 27, p = 0.001).
Performance on the WAB word recognition was significantly correlated with
the aphasia quotient (r = 0.688, n = 27, p = <0.001) and gender (r = -0.562, n = 27, p =
0.002).
47
Table 1
Correlations for participants with aphasia
Age
Aphasia
Gender
MCTAC
Quotient
PALPA
WAB
WAB
WAB
WAB
Word
Command
Comp
Word
Y/N
Total
Rec.
Yrs.
Of
Educ.
-.067
.178
-.278
-.247
-.242
-.391*
-.303
-.202
.282
.207
.740
.376
.160
.233
.234
.044
.125
.311
.155
.300
27
27
27
27
25
26
27
27
27
27
27
Aphasia
-.067
1
-.368
.710**
.765**
.466**
.547**
.610**
.688**
.231
-.259
Quotient
.70
.192
Age
1
PALPA
Sentence
.059
.000
.000
.017
.003
.001
.000
.247
27
27
27
27
25
26
27
27
27
27
27
.178
-.368
1
-.533
-.515
-.163
-.377
-.422*
-.562**
-.045
-.267
.376
.059
.003
.008
.426
.052
.028
.002
.825
.178
27
27
27
27
25
26
27
27
27
27
27
-.278
.710**
-.553**
1
.780**
.387
.660**
.717**
.752**
.262
-.068
.160
.000
.003
.000
.051
.000
.000
.000
.187
.734
27
27
27
27
25
26
27
27
27
27
27
PALPA
-.247
.765**
-.515**
.780**
1
.558**
.808**
.819**
.679**
.337
-.165
Sentence
.233
.000
.008
.000
.004
.000
.000
.000
.100
.431
25
25
25
25
25
25
25
25
25
25
25
PALPA
-.242
.466*
-.163
.387
.558**
1
.521**
.515**
.437*
.127
-.297
Word
.234
.017
.426
.051
.004
.006
.007
.026
.535
.140
26
26
26
26
25
26
26
26
26
26
26
WAB
-.391*
.547*
-.377
.660*
.808**
.521**
1
.977**
.571**
.490**
.046
Command
.044
.003
.052
.000
.000
.006
.000
.002
.009
.820
27
27
27
27
25
26
27
27
27
27
27
WAB
-.303
.610**
-.422**
.717**
.819**
.515**
.977**
1
.691*
.581**
.037
Comp
.125
.001
.028
.000
.000
.007
.000
.000
.001
.855
27
27
27
27
25
26
27
27
27
27
27
WAB
-.202
.688**
-.562*
.752**
.679**
.437*
.571**
.691**
1
.196
-.027
Word
.311
.000
.002
.000
.000
.026
.002
.000
.326
.894
27
27
27
27
25
26
27
27
27
27
27
WAB
.282
.231
-.045
.262
.337
.127
.490**
.581**
.196
1
.045
Y/N
.155
.247
.825
.187
.100
.535
.009
.001
.326
27
27
27
27
25
26
27
27
27
27
27
Yrs. Of
.207
-.259
-.267
-.068
-.165
-.297
.046
.037
-.027
.045
1
Educ.
.300
.192
.178
.734
.431
.140
.820
.855
.894
.822
27
27
27
27
25
26
27
27
27
27
Gender
MCTAC
Total
Rec.
**. Correlation is significant at the 0.01 level (2-tailed)
*. Correlation is significant at the 0.05 level (2-tailed)
.822
27
48
Correlations for the control group
There was a significant correlation between education and gender (r = -0.370,
n = 40, p = 0.019), and age (r = 0.420, n = 40, p = 0.007). There was significant
correlation between performance on the MCTAC and PALPA subtest 47 (r = 0.434, n
= 40, p = 0.005), and performance on PALPA subtest 55 (r = 0.351, n = 40, p =
0.026).
Table 2
Correlations for participants without aphasia
Variables Correlated
Education and Gender
Education and Age
MCTAC and PALPA subtest 47
MCTAC and PALPA subtest 55
r, n, and p values
r = -0.370, n = 40, p = 0.019
r = 0.420, n = 40, p = 0.007
r = 0.434, n = 40, p = 0.005
r = 0.351, n = 40, p = 0.026
Hypotheses correlations
Hypothesis 1: There was no correlation between the WAB comprehension total
and the proportion of fixation duration on the target for working memory eye-tracking
task (r = -0.233, n = 27, p = 0.242).
Hypothesis 2: There was no correlation between PALPA subtest 55, auditory
sentence comprehension, and the proportion of fixation duration on the target for the
working memory eye-tracking task (r = -0.334, n = 25, p = 0.103).
Hypothesis 3: There was no correlation between PALPA subtest 47, spoken
word comprehension, and the proportion of fixation duration for working memory
eye-tracking task (r = -0.123, n = 26, p = 0.551).
49
Hypothesis 4: There was no significant correlation between performance on
the verbal working memory eye-tracking task and performance on the MCTAC (r = 0.021, n = 27, p = 0.918)
Table 3
Correlations for the hypotheses for participants with aphasia
Variables Correlated
WAB comprehension total
and proportion of fixation
duration for working
memory task
PALPA subtest 55 and
proportion of fixation
duration for working
memory task
PALPA subtest 47 and
proportion of fixation
duration for working
memory task
MCTAC and proportion of
fixation duration for
working memory task
r values
n values
p values
r = -0.223
n = 27
p = 0.242
r = -0.334
n = 25
p = 0.103
r = -0.123
n = 26
p = 0.551
r = -0.021
n = 27
p = 0.918
Other Correlations
There was a significant correlation between performance on the verbal
working memory eye-tracking task and performance on the eye-tracking auditory
sentence comprehension (r = 0.499, n = 27, p = <0.001).
Discussion
The first hypothesis was consistent with the previous findings from Ivanova &
Hallowell (2011), who found that there was no correlation between the proportion of
50
fixation duration for the eye-tracking verbal working memory task and the WAB
comprehension total. This result is consistent with Hypothesis 1, which said that there
would not be a correlation.
The second hypothesis was confirmed due to the lack of a significant
correlation between the proportion of fixation duration for the eye-tracking verbal
working memory task and PALPA subtest 55. As stated previously, it was theorized
that by using a more detailed index of auditory sentence comprehension a correlation
might be found amongst the verbal working memory eye-tracking data and the scores
from PALPA subtest 55; however, this was not the case. These results support the
theory that verbal working memory is not predictive of auditory comprehension
performance.
The third hypothesis was confirmed due to the lack of significant correlation
between the proportion of fixation duration for the eye-tracking verbal working
memory and subtest 47 of the PALPA. This subtest was included because of the
chance that some participants with aphasia would not be able to complete PALPA
subtest 55 because investigators were unaware of the severity of aphasia for the
participants in the aphasia group before meeting them. However, after the completion
of the data collection many participants with aphasia performed well on both subtests
of the PALPA.
The fourth hypothesis was confirmed due to the lack of significant correlation
between the proportion of fixation duration of the eye-tracking verbal working
memory and the MCTAC. This finding is consistent with the previous findings that
51
there is not a relationship between auditory sentence comprehension and verbal
working memory eye-tracking scores.
One explanation for why previous research found a relationship between
working memory and auditory comprehension is that none of the previous studies
(Friedmann & Gvian, 2003; Grossman & Moore (2005); Sung et al., 2009; Wright et.
al., 2007) utilized eye-tracking methods. Since the eye-tracking working memory task
did not utilize spoken language as most working memory indices do, this could
contribute to the lack of significant correlation. In addition, because eye-tracking
reduces the cognitive load required to use spoken language or motor function, such as
pointing, the use of eye-tracking could also contribute to the lack of correlation and
potentially lead to a more valid index of working memory in persons with aphasia.
The lack of significant correlations is consistent with the previous research of
Ivanova and Hallowell (2011). Together, these studies support the idea that there is no
relationship between performance on the eye-tracking verbal working memory task
and spoken language comprehension performance. However, future research is needed
to determine how working memory and language comprehension are related.
Examining this relationship from a new direction could potentially lead to a better
understanding of this relationship. For example, a relationship was found between the
processing component of the verbal working memory task and the storage component
of the verbal working memory task, meaning performance on one task related to the
performance on the other task. Based on these data, a new approach would be to
investigate a relationship between eye-tracking auditory comprehension scores and
52
eye-tracking verbal working memory scores. This idea brings to surface the concept of
testing modalities when comparing tasks. It is possible that when comparing two
different testing modalities, eye-tracking and traditional comprehension tasks,
relationships would not emerge because of the differences between the types of tasks.
Furthermore, previous studies (Friedmann & Gvian, 2003; Grossman & Moore
(2005); Sung et al., 2009; Wright et. al., 2007) have shown this effect when using
similar working memory tasks and auditory comprehension tasks . Contributory
differences between eye-tracking tasks and traditional tasks are that eye-tracking only
requires movement of the eyes and no other motor functions. In addition, eye-tracking
requires less reliance on language, and could thus be a more valid index of abilities in
persons with neurological impairments.
Another direction for future research is to evaluate an eye-tracking non-verbal
working memory task. The Ohio University Neurolingistics Laboratory team is
currently working on such a task. This task has the same protocol as the verbal
working memory task, but uses no language during the processing trials. Using a nonverbal working memory task could potentially provide a more direct method of
assessing working memory in persons with aphasia because language is removed from
the task. These scores could be compared to spoken language comprehension scores
from both traditional test batteries and eye tracking auditory comprehension tasks, to
see if any relationships are present.
In the first set of experiments an interesting finding emerged: the correlation
between gender and the MCTAC, PALPA subtest 55, WAB comprehension total, and
53
WAB word recognition. The PALPA test manual does not mention differences in
gender or possible gender effects. In addition, a literature review yielded no data
about gender effects on comprehension deficits. Moreover, the WAB manual does not
include a gender analysis run or a gender effect. However, a literature review
produced an article about the standardization of the WAB in Korean. In this article the
authors ran a gender analysis and found that there was not a gender effect for the
Korean WAB (Kim & Na, 2004).
After completion of a literature review, the data were reviewed for outliers that
would cause the data to be skewed from the normative data. Scores that were two
standard deviations away from the mean were removed, and the analysis was run
again. There were a total of six scores removed. All scores that fell two standard
deviations below the mean were from female participants. However, even after the
removal of the outliers, the gender effect remained. When the data were examined
further, the averages for the male participants on the language comprehension tasks
were higher than the averages of the females. In addition, when looking specifically at
the aphasia quotient from the WAB, which classifies persons with aphasia as mild,
moderate and severe, there were more females in the severe category. Aphasia
quotients for each participant are in Appendix B. It is also important to note that there
were only 10 female participants and 18 male participants, which can lead to skewed
comparisons. However based on the performance of comprehension tasks and the
aphasia quotients, it is reasonable to conclude for the participants in this study that
54
overall the males had generally less severe forms of aphasia than the female
participants.
Overall, the results supported the previous findings from Ivanova and
Hallowell (2011). However, there is still a need for future research in how auditory
comprehension and working memory are related in persons with aphasia.
Understanding this relationship can improve the knowledge about aphasia treatments
and assessment, in addition to possibly redefining aphasia. Currently, aphasia is
typically defined as strictly a language problem; however, if non-linguistic cognitive
processes are also impaired then it may be important to include such deficits in the of
aphasia. Second, if non-linguistic cognitive deficits contribute to the language
comprehension difficulties in persons with aphasia, focusing on deficits in areas like
working memory could help to improve language comprehension in persons with
aphasia. Finally, it is important for future research to focus on assessing working
memory, in addition to auditory comprehension, in order to investigate methods that
truly evaluate a person’s working memory capacities, regardless of the presence of
neurological impairment.
55
References
Baddeley, A.D., & Hitch, G.J. (1974). Working Memory. In G.H. Bower (Ed.), The
psychology of learning and motivation: Advances in research and theory (pp.
647-667). New York: Academic Press.
Caspari, I., Parkinson, S.R., LaPointe, L. L., & Katz, (1998). Working memory and
aphasia. Brain and Cognition 37, 205-223.
Caplan, D., & Walters, G. S., (1996). Syntactic processing in sentence comprehension
under dual-task conditions in aphasic patients. Language and Cognitive
Processes, 11 (5), 525-551.
Caplan, D., & Walters, G. S., (1999). Verbal working memory capacity and language
comprehension. Behavioral BrainSciences, 22, 77-94.
Cowan, C., Elliot, E.M., Saults, J.S., Morey, C.C., Mattox, S., Hismjatullina, A., &
Conway, A.R., (2005). On the capacity of attention: Its estimation and its role
in working memory and cognitive aptitudes. Cognitive Psychology, 51(1), 42100.
Daneman, M., & Carpenter, P., (1980). Individual differences in working memory and
reading. Psychological Review, 82, 407-428.
Friedmann, N., & Gvion, A., (2003). Sentence comprehension and working memory
limitation in aphasia: A dissociation between semantic-syntactic and
phonological reactivation. Brain and Language, 86, 23-39.
56
Folstein, M.F., Folstein, S.E., & McHugh, P.R., (1975). "Mini-mental state". A
practical method for grading the cognitive state of patients for the clinician.
Journal of Psychiatric Research, 12, 189-198.
Grossman, M., & Moore, P. (2005). A Longitudinal study of sentence comprehension
difficulty in primary progressive aphasia. Neurol Neurosrug Psychiatry, 76,
644-649.
Hallowell, B. (2011). The Multiple-Choice Test of Auditory Comprehension in
English. Unpublished manuscript.
Hallowell, B., & Chapey, R. (2008). Introduction to language intervention strategies in
adult aphasia. Language Intervention Strategies in Adult Aphasia. Chapey, R.
(Ed.), 5th Edition. Baltimore: Williams & Wilkins, pp. 3-19.
Hallowell, B., Wertz, R., & Kruse, H., (2002). Using eye movement responses to
index auditory comprehension: An adaption of the Revised Token Test.
Aphasiology, 16, 587-594.
Hasher, L., & Zacks, R., (1988). Working Memory, comprehension, and again: A
review and view. The Psychology of Learning and Motivation, 22, 193-223.
Howard, D., & Patterson, K.E. (1992). The Pyramids and Palm Trees Test. Bury St.
Edmunds, UK: Thames Valley Test Company.
Ivanova, M.V. & Hallowell, B. (2011). Validity of an eye-tracking method to index
working memory in people with and without aphasia. Unpublished manuscript.
57
Kay, J., Lesser, R., & Coltheart, M. (1992). PALPA: Psycholinguistic Assessments of
Language Processing in Aphasia. Hove, UK: Lawrence Erlbaum Associates
Ltc.
Kay, J., & Terry, R.., (2004). Ten years on: Lessons learned from published studies
that cite the PALPA. Aphasiology, 18, 127-151.
Kertesz, A. (2007). Western Aphasia Battery-Revised. San Antonio, TX: Harcourt
Assessment.
Kim, H. & Na, D.L., (2004). Normative data on the Korean version of the Western
Aphasia Battery. Journal of Clinical and Experimental Neuropsychology,
26(8), 1011-1020.
LaPointe, L.L., & Horner, J. (1979). Reading comprehension battery for aphasia.
Austin, TX: Pro-Ed.
LC Technologies, Inc., (2009). How does the eye gaze edge work?. Retrieved from
http://www.eyegaze.com/content/how-does-eyegaze-edge-work
LC technologies, Inc. (2009). Instrument Specifications. Retrieved from
http://www.eyegaze.com/content/instrument-specifications
Love, T., & Oster, E., (2002). On the categorization of Aphasic types: The S.O.A.P., a
test of syntactic complexity. The Journal of Psycholinguistic Research, 31,
503-529.
McNeil, M. R., & Prescott, T.E. (1978). Revised Token Test. Austin, TX: Pro-Ed.
Riddoch, M. J., & Humphreys, G.W. (1993). BORB: The Birmingham Object
Recognition Battery. Hove, UK: Lawrence Erlbaum Associates Ltd.
58
Sung, J.E., McNeil, M.R., Pratt, S.R., Dickey, M.W., & Hula, W.D. (2009).Verbal
working memory and its relationship to sentence-level reading and listening
comprehension in persons with aphasia. Aphasiology, 23, 1040-1052.
Wright, H. H., Downey, R.A., Gravier, M., Love, T., & Shapiro, L.P. (2007).
Processing distinct linguistic information types in working memory in aphasia.
Aphasiology, 21, 802-813.
Wright, H. H., & Shisler, R.J., (2005). Working memory in aphasia: Theory,
measures, and clinical implications. American Journal of Speech-Language
Pathology 14, 107-118.
59
Appendix A: Normative Data for PALPA Subtests
Table 1
Normative Data for PALPA Subtest 47
Number of Words
Mean number
correct
40
39.29
(Kay & Terry, 2004)
Standard Deviation
Range
1.07
35-40
Mean number
correct
19.42
15.61
7.74
7.22
7
Standard Deviation
Table 2
Normative Data for PALPA Subtest 55
Type of Sentence
Number of
Sentences
Reversible
20
Non-Reversible
16
Gap as Subject
8
Gap not as subject
8
Converse Relations
8
(Kay & Terry, 2004)
0.86
0.80
0.71
0.70
0.94
60
Appendix B: Comprehension tasks scores for participants with Aphasia
Table 4
Aphasia Quotients for Participants
Sex
Female
Female
Female
Female
Female
Female
Female
Female
Female
Female
Female
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
WAB Aphasia
Quotient
47.5
61.1
62.5
70.9
72.6
75
77.4
81.1
89.4
90
91.8
61.1
62.5
70.6
76
76.3
77.5
78
79.4
85.3
89.2
91.8
92.2
94.8
95.2
96.2
99