Running head: EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Effect of Repetition on False Memory for Same- and Cross-Race Faces
A thesis submitted to the Miami University
Honors Program in partial fulfillment of the
Requirements for University Honors with Distinction
by
Meghan Royer
Miami University
Oxford, OH
2011
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Abstract
The study will investigate the use of frequency estimation strategy on accurately identifying
same-race and cross-race faces. Previous research shows that people have difficulty when
recognizing cross-race faces compared to same-race faces. When encoding information such as
faces, people use multiple strategies: familiarity and recollection. Previous research has shown
that as presentation frequency increases, participants are able to switch from a familiarity-based
strategy to a recollection-based strategy. This change increases the accuracy of frequency
estimates for previously seen faces and for related, yet previously unseen, faces (false
memories). The current study looks at the dependant variable of false memory to study when
participants switch strategies from familiarity-based to recollection-based. True target faces
were seen during the study phase of the experiment, and participants were later tested on how
many times each face had been seen. The test phase also included faces that were never seen
before which featured half of the characteristics of the study phase to act as false targets.
However, an error on the part of the experimenter prevented analyses from being conclusive.
Overall, there were no significant differences in recognition or frequency estimation accuracy for
true or false targets as a function of race.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Approved by:
_________________________________, Advisor
Dr. Peter Wessels
_________________________________, Reader
Dr. Amanda Diekman
_________________________________, Reader
Alexandria Intorcio
Accepted by:
_________________________________, Director of University Honors Program
Dr. Carolyn A. Haynes
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Acknowledgements
I would like to thank my advisor, Dr. Peter Wessels, for his support throughout my
project. He allowed me to use his lab space, computers, and resources to complete the project.
Without his help, my thesis work would not have been possible. I would also like to thank Dr.
Robin Thomas for allowing me use of her computers and software, which also made my project
possible. Furthermore, I am grateful to the Office for the Advancement of Research and
Scholarship at Miami University for funding my project through an Undergraduate Summer
Scholars grant.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Introduction
The ability to identify another person’s face and use that information to guide our
behavior is a critical component of social interaction. However, there are many factors in
memory that influence how well we remember another’s face. For example, how many times the
face has been seen before can play a role in memory. The person’s race can also influence how
well a face is remembered. When this information is not encoded thoroughly, misidentification
can occur which can result in the formation of false memory. False memories can be extremely
detrimental in the case of eyewitness testimony since the wrong person could be identified and
even incarcerated for a crime he did not commit. People use different memory strategies
depending on how many times a face has been seen, and one of these strategies, recollection, is
less likely to lead to false memory errors than the other, familiarity. The present study
specifically looks at the dependent variable of false memory to study when participants switch
strategies from familiarity-based to recollection-based and how this differs as a function of race.
How race affects memory for faces is described by the Cross-Race Effect. The CrossRace Effect (CRE) describes the phenomenon of how people have difficulty recognizing faces of
a different race (members of their out-group) compared to same-race (in-group) faces (Malpass
& Kravitz, 1969). Overall, people are more accurate at identifying same-race faces. The CRE
has many implications for how faces are processed in memory. Specifically, Meissner and
Brigham (2001) have shown that white participants are more likely to show a same-race bias by
more correctly identifying same-race faces and incorrectly identifying cross-race faces. This
happens when people incorrectly believe they have seen the face before (Meissner & Brigham,
2001). While the exact cause of the CRE is still being explored, early accounts of the CRE
argued that this memory deficit for cross-race faces is driven by a lack of expertise for
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
processing cross-race faces. In other words, people may be more experienced at processing faces
of their in-group and less skilled at processing features of out-group faces (Meissner & Brigham,
2001). However, the CRE may instead be due to a different categorization process for out-group
faces than for in-group faces. Specifically, in-group faces may benefit from processing that is
driven by a motivation to notice distinguishing features, whereas out-group faces tend to be
characterized by general features of the race (Hugenberg, Miller, and Claypool, 2007;
Hugenberg, Young, Bernstein, and Sacco, 2010).
When storing information in memory like faces, people may use multiple encoding
strategies. According to Brown (1995), the default, low-effort strategy relies on vague feelings
of familiarity. Familiarity does not require many resources and tends to produce overestimation
of frequency. A more effortful strategy, in which individual episodes are retrieved and counted,
relies on recollection and can be used when people are motivated. Recollection is only used
when participants view information as important or relevant. According to Greene (1989), when
people begin using recollection, this signifies the onset of study-phase retrieval. Study-phase
retrieval occurs when the repetition of a stimulus reminds the participant of specific earlier
presentations. Study-phase retrieval works better when presentations of the stimulus are spaced
because that allows the participant to create episodic information for each presentation.
Therefore, each stimulus presentation can be distinguished in memory (Greene, 1989).
Strategy use depends on the number of presentations of a stimulus. Studies of word
recognition have shown that as the presentation frequency (i.e., repetition) of a word increases,
participants seem to switch from a familiarity-based strategy to a recollection-based strategy
(Hall & Kozloff, 1970). This change in processing strategy leads to higher accuracy when people
are asked to estimate how many times repeated information has been seen. Brown (1995)
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
showed that participants’ frequency estimates for studied words became more accurate when
participants based their estimates on retrieved and counted episodes instead of familiarity-based
guesses. Switching to a recollection strategy instead of a familiarity strategy also leads
participants to suppress false memories for related, but unstudied, words (Hall & Kozloff, 1970).
When this switch in memory strategy happens depends on the number of repetitions of the
stimulus. Hall and Kozloff (1970; 1973) have shown that a false target, an item that has not been
presented before but has been elicited by the earlier presentation of a related item, is more likely
to elicit a false memory at low presentation frequencies when participants are relying on
familiarity. This occurs mostly between one and three repetitions. After three repetitions,
however, participants implicitly switch their strategy to recollection, making them better at
recognizing false targets (Hall & Kozloff, 1970). The more times the stimulus is presented, the
more once can recall specific episodes of that stimulus.
While most research has studied the effect of word repetition on frequency estimation
strategy, previous research has also shown the same relationship when the repeated stimuli are
faces. A previous study has indicated that the accuracy of frequency estimates is better for ingroup faces than for out-group faces regardless of race (Royer, Young, Wessels, & Hugenberg,
2010). The same improved accuracy of frequency estimates was seen both when White faces
constituted the in-group and Black faces were the out-group, and when White faces only were
artificially put into in-groups and out-groups. Like with words, the accuracy of frequency
estimates for any face is dependent on how many times the face has been presented. The more
times the face has been presented, the more likely the participant is to make an accurate
frequency estimate and the better able he or she is to notice that false stimuli have not previously
been presented. This creates a large disparity in feelings of recollection for participants, and they
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
become better able to attribute false targets as never seen before (Hall & Kozloff, 1970).
Participants use that disparity to suppress false memories.
Taking into account these previous findings, the present study looks to extend the body of
research to answer how in-group and out-group faces are processed differently in the brain.
Specifically, I will measure the dependant variable of false memory to study when participants
switch strategies from familiarity-based to recollection-based. This will also show whether
switching to a recollection strategy suppresses more false memories for faces than using a
familiarity strategy. I hypothesize that while recognition of studied faces will increase with the
number of presentations, the false recognition of false targets will at first increase, but then
decrease (Hall & Kozloff, 1970). That switch in false face processing will be a strong indicator
of when the participants have switched from a familiarity-dominated strategy to one that includes
recollection. Due to the CRE, this switch should happen earlier for in-group faces than outgroup faces. Also, out-group faces should be more likely to elicit false memories than in-group
faces.
Method
Participants and Design. Forty five undergraduates who were at least 18 years old who had
normal or corrected to normal vision at Miami University participated for partial course credit.
These participants were volunteers from the Introduction to Psychology participant pool. Four
participants were excluded from analysis because they failed to follow instructions. Participants
viewed 84 White and 84 Black faces at varying presentation frequencies during the study phase.
The design was 2 (Target Race: White, Black) x 6 (Level of Repetition: 0, 1, 3, 5, 7, 9). All of
the White faces were viewed in sequence followed by all of the Black faces, and this order was
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
counterbalanced between-subjects. During the test phase, participants estimated how many
times each face was presented during the study phase.
Materials. Stimuli were drawn from a pool of 168 face pairs. Each pair consists of a true target
face to act as an eliciting stimulus to be seen during the study phase and a face that was used to
create a false stimulus and was never seen during any part of the experiment (see Appendix A).
These are images of neutral-expression male faces found in the Tampa Bay Mugshot Index, a
public domain website. The faces were adapted to a generic face model using FaceGen Modeller
3.4 software. Images are in grayscale with a gray background, 3x3 inches in size, and only
display the face and neck. From the faces pairs, 168 false target faces (84 Black; 84 White) were
created by blending the cue face and the target face using FaceGen.
Procedure. After providing informed consent, participants were seated in individual cubicles.
They were instructed that they would be participating in a face recognition experiment consisting
of study and test phases. Instructions and stimuli were presented via computer (see Appendix
B). Before the study phase, every participant viewed the same instructions to try to remember
each face that was shown. Fourteen faces were used as buffers during the study phase of the
experiment (seven to reduce primacy and seven to reduce recency effects). The buffer faces
were the same for all participants, were always presented in the same position, and never
appeared during the test phase. The 168 face pairs were randomly assigned to six conditions
during which the cue face appeared at varying frequencies (1, 3, 5, 7, 9, or 0 times). Each face
pair had an equal chance of serving every condition. Another condition (the 2 condition) was
created in which both the cue and target from a face pair was presented during the study phase in
order to add face validity to the experiment. There were a total of 324 trials during the study
phase. Every trial began with a fixation cross for 250ms. Every participant viewed 12 faces (6
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Black; 6 White) one at a time for 3000ms at each level of repetition (1, 2, 3, 5, 7, or 9 times).
Presentations were separated by a minimum of 9 trials and a maximum of 15.
Finally, all participants completed the test phase. Participants were instructed to use the
keyboard to enter a number 0 through 9 indicating how many times they had seen each face
during the study phase (see Appendix B). They were told that they should respond as accurately
and quickly as possible. The 84 total faces observed during the test phase were chosen randomly
and due to an error, included unequal numbers of faces that had been seen before and faces that
were new. As a result, participants were tested on 39 faces viewed during the learning phase (20
Black; 19 White) and 45 false target faces that have not been seen before (22 Black; 23 White).
The faces appeared in the same order for each participant. Each face was presented one at a time
until the participant responded, after which the next face was presented.
Results
Recognition Accuracy Analysis. Recognition scores were analyzed in order to study if
recognition of studied faces increased with the number of presentations and if false recognition
of false targets decreased with increasing numbers of presentations as hypothesized. In order to
calculate recognition scores, all of the faces were sorted according to stimulus class. Each
stimulus class should have been represented by six faces (3 White; 3 Black) during the test
phase. However, due to a coding error, each level was represented unequally (see Appendix C).
One condition, the White Veridical Recognition at 5 levels of repetition (WVR5) had 0 faces
represented, so for the sake of statistical analysis, the recognition data were artificially created
for this condition by averaging the data for the WVR3 and WVR7 conditions. As a result of this
error, the recognition scores are disproportionate and statistical analysis is not meaningful.
However, a 2(Target Race: White, Black) x 5 (Level of Repetition: 1, 3, 5, 7, 9) repeated
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
measures ANOVA was still conducted to see if there was a significant interaction. All 0
frequency estimates were re-coded as “new” since they were never seen before the test phase.
All non-zero frequency estimates were considered “old” as the participant indicated that he or
she had seen that face at least once before. Corrected recognition rates were calculated by
subtracting the error rates from control stimuli (faces that were not studied but presented during
the test phase). Due to the coding error, this created some negative recognition scores, which
should not have been possible. These numbers skew the results and make any significant
findings meaningless.
A 2(Target Race: White, Black) x 5 (Level of Repetition: 1, 3, 5, 7, 9) repeated measures
ANOVA was conducted for studied faces and false targets that have already been corrected for
error. For studied faces, there was no significant Target Race x Level of Repetition interaction,
Proportion of correct
"old" responses (%)
F(2, 40) = 1.64, p = .185. See figure 1 for a summary of results.
0.3
0.25
0.2
0.15
0.1
0.05
0
White Targets
Black Targets
1
3
5
7
9
Presentation Frequency
Figure 1. Recognition accuracy for true targets.
For false faces, there was a significant Target Race x Level of Repetition interaction, F(2, 40) =
5.19, p = .002. There was also a main effect of level, F(2, 40) =5.31, p = .002. Despite the
significant results for an interaction of race and level for false faces, the coding error influenced
the data heavily and skewed the results. See figure 2 for a depiction of these results.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Proportion of correct
"old" responses (%)
0.1
0
-0.1
1
3
5
7
9
Black Targets
-0.2
-0.3
White Targets
Presentation Frequency
Figure 2. Recognition accuracy for false faces.
Frequency Estimate Accuracy Analysis. Frequency estimates were analyzed in order to study
how many repetitions of a face are necessary before people switch from a familiarity-based
strategy to a recollection-based strategy. It was hypothesized that the switch in processing would
be signified by a non-monotonic pattern in the data, where people at first overestimate the
number of times they have seen a face, but then underestimate presentation frequency as the
number of repetitions increase. I hypothesized this switch would happen earlier for in-group
faces than for out-group faces. For false faces, I predicted that out-group false faces would have
less accurate frequency estimation scores than in-group false faces. To evaluate the accuracy of
frequency estimates, the average estimate for each participant for each stimulus class was used.
A 2(Target Race: White, Black) x 5 (Level of Repetition: 1, 3, 5, 7, 9) repeated measures
ANOVA was conducted to look for a significant interaction between target race and level of
repetition for frequency estimates. For true target faces, there was a significant Target Race x
Level of Repetition interaction, F(2, 40) = 25.4, p = .000. There were also main effects for level,
F(2, 40) = 18.75, p = .000 and race, F(2, 40) = 11.02, p = .002. These results are depicted in
figure 3.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Frequency Estimates
9
8
7
6
5
4
3
2
1
0
Optimum
White
Targets
Black
Targets
1
3
5
7
9
Presentation Frequency
Figure 3. Frequency estimate accuracy for true targets.
There was no significant Target Race x Level of Repetition interaction for false faces, F(2, 40) =
1.76, p = .158. For false faces, there was a main effect of race F(2, 40) = 7.92, p = .008. These
Frequency Estimates
results are depicted in figure 4.
8
6
White
Targets
Black
Targets
4
2
0
1
3
5
7
9
Cue Face Presentation Frequency
Figure 4. Frequency estimate accuracy for false targets.
A t-test was also conducted to study if there was a significant difference of race at each level of
repetition. There was a significant finding was that at one level of repetition for true targets,
estimates for white faces were significantly different than estimates for black faces, t(40)=-4.97,
p = .000. At one level of repetition for false targets there was a also a significant effect for race
t(40)=-2.34, p=.024.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Discussion
This study sought to extend previous research on study-phase retrieval and the CrossRace Effect. Participants viewed in-group and out-group faces to study how they are processed
differently in the brain and when participants switch from a familiarity strategy to a recollection
strategy. The study was also meant to show how these memory strategies affect the processing
of false faces. I predicted that recognition of studied faces would significantly increase with the
number of presentations, and false recognition of false targets would decrease with the number
of presentations. I also hypothesized that the switch in memory strategy would happen earlier
for in-group than for out-group faces. Out-group faces were expected to be more likely to elicit
false memories than in-group faces.
My findings do not support my hypotheses. There was no significant difference in
recognition for in-group versus out-group faces for true targets. Statistically there was a
significant difference in recognition for in-group versus out-group for false targets, but this
relationship only existed due to an error on the part of the experimenter. There was a significant
difference in frequency estimate accuracy for true targets, but again this relationship was likely
only visible due to the coding error. There was no significant difference in frequency estimate
accuracy for false targets. There was no observable switch in memory strategy for in-group or
out-group faces. Furthermore, out-group faces were not significantly more likely to elicit a false
memory than in-group faces.
This study had several different factors that acted as limitations and affected the results.
These limitations include the fact that there were an unequal number of faces in each stimulus
class and there was only one counterbalancing condition. Due to time constraints, there were
only two conditions programmed. The first condition showed participants only white faces 1
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
through 84 of the 168 created and then black faces 1 through 84 of the 168 black faces created.
The second condition showed only black faces 1 through 84 followed by white faces 1 through
84. To add validity to the experiment, there should have been additional conditions that used
faces 85-168 for white and black faces. Furthermore, when running pilot subjects, the data
output was never checked to make sure the faces used during the test phase correctly showed
three faces for each stimulus class for each race. If this step had been taken, statistical analysis
would have been more likely to reveal actual significant effects, if any were present. Also, more
participants should have been used to increase the likelihood of finding significant results.
Given these improvements, a future study may find significant results that could
contribute to the knowledge of memory strategies and their use in suppressing false memories for
in-group and out-group faces. This knowledge could be used to help individuals learn how to
better remember faces, resulting in fewer misidentifications. In the case of eyewitness
testimony, false memories can be very detrimental and result in an innocent person been
identified and found guilty of a crime he or she did not commit. Future experiments in this field
can shed light on the unreliability of eyewitness testimony.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
References
Brown, N. R. (1995). Estimation strategies and the judgment of event frequency. Journal of
Experimental Psychology: Learning, Memory, and Cognition, 21(6): 1539-1553.
Greene, R. L. (1989). Spacing effects in memory: Evidence for a two-process account. Journal
of Experimental Psychology: Learning, Memory, and Cognition, 15(3): 371-377.
Hall, J. W. & Kozloff, E. E. (1970). False recognitions as a function of number of presentations.
American Journal of Psychology, 83: 272-279.
Hall, J. W., & Kozloff, E. E. (1973). False recognitions of associates of converging versus
repeated words. American Journal of Psychology, 86(1), 133-139.
Hugenberg, K., Miller, J., & Claypool, H. M. (2007). Categorization and individuation in the
cross-race recognition deficit: Toward a solution to an insidious problem. Journal of
Experimental Social Psychology, 43(2): 334-340.
Hugenberg, K., Young, S. G., Bernstein, M. J., & Sacco, D. F. (2010). The categorizationindividuation model: An integrative account of the other-race recognition deficit.
Psychological Review, 177(4): 1168-1187.
Malpass, R. S. & Kravitz J. (1969). Recognition for faces of own and other race. Journal of
Personality and Social Psychology, 13(4): 330-334.
Meissner, C. A. & Brigham, J. C. (2001). Thirty years of investigating the own-race bias in
memory for faces: A meta-analytic review. Psychology, Public Policy, and Law, 7: 3–35.
Royer, M. N., Young, S. G., Wessels, P. W., & Hugenberg K. (2010). Effect of repetition on
frequency estimates for ingroup and outgroup faces. Unpublished: poster presented at
Midwestern Psychological Association in Chicago, IL.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Underwood, B. J. (1965). False recognition produced by implicit verbal responses. Journal of
Experimental Psychology, 70: 122-129.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Appendix A. Example of face pairs used to create false faces using FaceGen Modeller 3.4
Software.
True Target face
False Target
Face for Blending
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Appendix B. Experiment instructions as presented via computer.
Study Phase Instructions
Welcome to the Experiment.
In the “study phase” of the experiment, you will see a series of faces on the computer screen.
Try your best to remember each face. You will be tested on them later.
When you are ready to begin, press the spacebar.
Test Phase Instructions
You will now be shown a series of faces. Some of them you will have seen before and some of
them will be new.
After each face appears on the screen, please use the numbers on the top row of the keyboard (0
through 9) to indicated the number of times you viewed that face during the “study phase” of the
experiment.
You may take as much time as you need to estimate the number of times you have seen each
face, but please make your estimate as quickly as you can while being as accurate as possible.
The next image will appear after you enter your estimate.
Remember to enter a number (0 through 9) using the top row on the keyboard after each face
appears.
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EFFECT OF REPTITION ON FALSE MEMORY FOR SAME- AND CROSS-RACE FACES
Appendix C. Expected vs. actual number of faces that appeared in each condition during the test
phase.
Stimulus Class
Expected # of Faces
WVR0 (error)
3
WVR1
3
WVR3
3
WVR5
3
WVR7
3
WVR9
3
WFR0 (error)
3
WFR1
3
WFR3
3
WFR5
3
WFR7
3
WFR9
3
BVR0 (error)
3
BVR1
3
BVR3
3
BVR5
3
BVR7
3
BVR9
3
BFR0 (error)
3
BFR1
3
BFR3
3
BFR5
3
BFR7
3
BFR9
3
W vs. B: White vs. Black
VR vs. FR: Veridical Recognition vs. False Recognition
Actual # of Faces
5
6
5
0
3
2
1
3
1
6
3
4
3
5
3
5
3
2
3
4
3
2
3
4
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