Capstones, Theses and
Dissertations
2018
Belief perseverance: The staying power of
confession evidence

TABLE OF CONTENTS
Page
LIST OF FIGURES ……………………………………………………………………………………… v
LIST OF TABLES……………………………………………………………………………………….. vi
ACKNOWLEDGMENTS …………………………………………………………………………….. vii
ABSTRACT……………………………………………………………………………………… viii
CHAPTER 1. INTRODUCTION…………………………………………………………………… 1
Error and Bias………………………………………………………………………………………… 2
Belief Perseverance…………………………………………………………………………………. 3
The Power of Confession Evidence…………………………………………………………… 5
Ambiguity ………………………………………………………………………………………… 7
Commitment …………………………………………………………………………………….. 7
Research Overview and Hypotheses………………………………………………………….. 8
CHAPTER 2. METHOD ………………………………………………………………………………. 10
Power Analysis ………………………………………………………………………………………. 10
Participants…………………………………………………………………………………………….. 10
Design …………………………………………………………………………………………………… 11
Crime Report………………………………………………………………………………………….. 11
Measures……………………………………………………………………………………………….. 12
Guilt Judgments………………………………………………………………………………… 12
Perceptions of Impartiality………………………………………………………………….. 12
Manipulation Check…………………………………………………………………………… 12
Attention Check ………………………………………………………………………………… 13
Suspicion Check………………………………………………………………………………… 13
Scrambled Anagrams…………………………………………………………………………. 14
Procedures……………………………………………………………………………………………… 14
CHAPTER 3. ANALYSES …………………………………………………………………………… 16
Preliminary Analyses………………………………………………………………………………. 16
Descriptive Statistics………………………………………………………………………….. 16
Commitment Manipulation Check……………………………………………………….. 16
Confession Timing Manipulation Check………………………………………………. 16
Attention Check ………………………………………………………………………………… 17
Suspicion Check………………………………………………………………………………… 17
Analytic Plan………………………………………………………………………………………….. 17
Model 1: Total Effect of Confession Timing on Phase 2 Guilt Judgments… 18
Model 2: Belief Perseverance Effect ……………………………………………………. 19
Path a: Confession Effect……………………………………………………………………. 19
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Path b: Judgment Stability ………………………………………………………………….. 20
Path a × b: Belief Perseverance …………………………………………………………… 20
Path c: Adding Confession Evidence and Procedural Effects………………….. 20
Moderation of Belief Perseverance by Commitment………………………………. 22
Main Analyses ……………………………………………………………………………………….. 22
Model 1: Total Effect of Confession Timing…………………………………………. 22
Model 2: Belief Perseverance Effect ……………………………………………………. 23
Path a: Confession Effect……………………………………………………………………. 24
Path b: Judgment Stability ………………………………………………………………….. 24
Path a × b: Belief Perseverance …………………………………………………………… 25
Path c: Adding Confession Evidence and Procedural Effects………………….. 25
Path a × b + c: Total Effect of Confession Evidence………………………………. 25
Moderation of Belief Perseverance by Commitment………………………………. 26
CHAPTER 4. DISCUSSION…………………………………………………………………………. 27
Belief Perseverance…………………………………………………………………………………. 27
Commitment ………………………………………………………………………………………….. 29
Accountability………………………………………………………………………………………… 29
Limitations…………………………………………………………………………………………….. 30
Conclusion …………………………………………………………………………………………….. 31
REFERENCES ……………………………………………………………………………………………. 33
APPENDIX A. PHASE 1 CRIME REPORT: CONFESSION EARLY………………. 45
APPENDIX B. PHASE 1 CRIME REPORT: CONFESSION LATE …………………. 47
APPENDIX C. PHASE 2 CRIME REPORT …………………………………………………… 48
APPENDIX D. GUILT JUDGMENTS…………………………………………………………… 52
APPENDIX E. PERCEPTIONS OF IMPARTIALITY …………………………………….. 53
APPENDIX F. MANIPULATION CHECK ……………………………………………………. 54
APPENDIX G. ATTENTION CHECK…………………………………………………………… 55
APPENDIX H. SUSPICION CHECK…………………………………………………………….. 56
APPENDIX I. SCRAMBLED ANAGRAMS………………………………………………….. 57
APPENDIX J. INSTITUTIONAL REVIEW BOARD APPROVAL FORM……….. 58
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LIST OF FIGURES
Page
Figure 1. Participant Verdicts by Condition and Phase ……………………………………… 37
Figure 2. Model 1: Examination of Total Effects……………………………………………… 38
Figure 3. Model 2: Mediated Model Examining Indirect Effects………………………… 39
vi
LIST OF TABLES
Page
Table 1. Experimental Design………………………………………………………………………. 40
Table 2. Descriptive Statistics………………………………………………………………………. 41
Table 3. Correlations…………………………………………………………………………………… 42
Table 4. Correlations by Commitment Condition……………………………………………. 43
Table 5. Model 2 Path Coefficients ………………………………………………………………. 44
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ACKNOWLEDGMENTS
I would like to thank some of the incredible mentors I have encountered leading up to this
thesis. To Dr. Leora Dahl for inspiring me to study forensic psychology rather than English. To
Dr. Linda Hatt and the late Dr. Claire Budgen for the opportunity to be a part of a research team
as an undergraduate. To Dr. Michael Woodworth for his mentorship of my honours thesis. To
Dr. Jan Cioe for his friendship and guidance on how to be a better student, a better teacher, and a
better person. To Dr. Marcus Credé and Dr. Gary Wells for their advice throughout the crafting
of this thesis. And finally to my co-advisors, Dr. Max Guyll and Dr. Stephanie Madon, for their
constant support and encouragement, without which this thesis would not have been possible.
viii
ABSTRACT
This research examined whether a criminal confession causes people to discount
subsequently encountered exculpatory evidence. Participants (N = 238) read a crime report
across two phases and judged a suspect’s guilt after each phase. In phase 1, the crime report
presented circumstantial evidence indicative of the suspect’s guilt. In phase 2, exculpatory
evidence indicative of the suspect’s innocence was added. The crime report manipulated whether
participants received confession evidence during phase 1 (confession–early) or phase 2
(confession–late). In addition, some participants publicly committed to their phase 1 guilt
judgments prior to receiving the crime report in phase 2 (high commitment), whereas others did
not (low commitment). Results provided some support for the hypothesis that a confession biases
the way that people use subsequently encountered exculpatory evidence to judge a suspect’s
guilt; under conditions of low commitment, participants more often rendered guilty verdicts in
the confession–early conditions than the confession–late conditions. The results are discussed in
terms of police investigator and juror decision-making.
1
CHAPTER 1. INTRODUCTION
It is well-established that a confession, even a false one, is a highly incriminating form of
evidence (Kassin, 2008; Leo & Drizin, 2010). Confession evidence is more powerful than
eyewitness and character testimony (Kassin & Neumann, 1997), and can even attenuate the
formidable power of DNA evidence under some conditions (Appleby & Kassin, 2016). Jurors
will sometimes convict defendants on the basis of confession evidence alone, and they do not
appropriately discount confessions that they believed were obtained under duress or that were
ruled inadmissible (Kassin et al., 2010; Kassin & Sukel, 1997; Smalarz, Madon, Yang, Guyll, &
Buck, 2016). Not surprisingly, jury conviction rates for false confessors are very high, ranging
from 73% – 81% (Drizin & Leo, 2004; Ofshe & Leo, 1997).
The power of confession evidence stems, in large part, from the widespread belief that
suspects, motivated by self-interest, would not confess to crimes that they did not commit unless
subjected to physical abuse or torture (Kassin & Wrightsman, 1981). However, psychological
research findings and proven false confession cases reveal this belief to be a misconception.
Innocent suspects do sometimes confess to crimes that they did not commit. In fact, false
confessions are a leading cause of wrongful convictions in the United States, contributing to the
convictions of nearly 28% of defendants who were later exonerated by DNA evidence (“DNA
Exonerations Nationwide,” 2016).
Although the widespread belief that false confessions only arise under egregious
circumstances is not true, it hints at the way that error and bias may contribute to the power of
confession evidence. That is, once people learn that a suspect has confessed, they may develop
such a strong belief in the suspect’s guilt that they fail to appropriately adjust their guilt
judgments in response to subsequently encountered evidence that points to the suspect’s
2
innocence. In psychological terms, a confession may elicit belief perseverance – a cognitive bias
in which people cling to their original beliefs even when the basis for the belief has been
discredited (Nestler, 2010). The idea that belief perseverance may contribute to the power of
confession evidence has been hypothesized by legal scholars (Findley & Scott, 2006), but has not
been empirically demonstrated.
Error and Bias
Social psychology has long emphasized the role that error and bias play in perception.
This emphasis dates back at least as far as the 1940s and 1950s when New Look in Perception
researchers proposed that people’s motivations, needs, goals, and expectations colored their
perceptions of reality (Bruner, 1992; Erdelyi, 1974). Bruner and Goodman (1947) provide a
classic illustration of this theoretical perspective. They presented 10-year-old children with coins
of varying values. In general, the children tended to overestimate the size of the coins, and this
tendency increased as the value of the coins increased. For example, children overestimated the
size of a penny by approximately 15%, whereas they overestimated the size of a quarter by more
than 35%. These results showed that the children’s perceptions of the coins were influenced by
their internal psychological states.
As a result of findings such as these, social and behavioral scientists turned their attention
to the way that biases may distort judgment and decision-making. Kahneman and Tversky
(1973), for instance, introduced numerous cognitive biases and heuristics, and in doing so called
into question the prevailing view that people rely on formal statistical rules to make social
inferences. For example, they argued that rather than using base rates to make judgments, people
instead have a tendency to make judgments on the basis of similarity, that people infer the
frequency of events according to the ease with which examples come to mind, and that people
3
are not sufficiently sensitive to the impact of sample size on probability judgments. The idea that
people rely on heuristics when making judgments sparked considerable interest in cognitive
biases and the way in which these biases may distort perception.
Belief Perseverance
Of particular importance to the current research is the cognitive bias of belief
perseverance. As previously noted, belief perseverance is the tendency for people to cling to their
initial beliefs even after the foundation supporting those beliefs has been discredited (Nestler,
2010). Numerous studies in the basic psychological literature have demonstrated this effect, with
most relying on what is commonly referred to as the debriefing paradigm.
The debriefing paradigm involves two groups of participants who receive conflicting
information about a topic. Participants in both groups subsequently learn that the information
they received is false, after which they make judgments relevant to the discredited information.
Although logically, participants should not use the discredited information to make their
judgments, the literature consistently shows that they do. For example, following a
discrimination task, participants who received positive feedback rated themselves as having
greater discrimination abilities than participants who received negative feedback despite that all
participants had earlier been informed that the feedback was false (Ross, Lepper, & Hubbard,
1975). Similarly, participants who were initially informed of a positive relationship between risktaking and being a successful firefighter continued to rate risky behavior as diagnostic of
firefighting success despite having already been debriefed to the false nature of the relationship
(Anderson, Lepper, & Ross, 1980).
A key strength of the debriefing paradigm is that it permits a decisive test of the belief
perseverance effect. That is, because the information on which participants based their initial
4
beliefs was completely discredited, any subsequent between-group difference in judgments that
is in the direction of the discredited information shows that participants inappropriately used the
discredited information. However, it is important not to equate the paradigm with the effect.
Even though the debriefing paradigm involves the complete discrediting of information, the
concept of belief perseverance does not. Failure to revise a belief when the information on which
it was based has been partially discredited is also irrational and also constitutes belief
perseverance. In addition, restricting the concept of belief perseverance only to situations
involving the complete discrediting of information raises conceptual problems. Most notably, it
would mean that beliefs that persevered in the context of less than completely discredited
information could not, by definition, indicate belief perseverance. This would be the case even if
the degree of discrediting was as high as 99%, and even though the underlying psychological
process responsible for the effect is indistinguishable from the process that operates when the
degree of discrediting is complete.
In fact, psychological theory never conceptualized belief perseverance as restricted to
situations involving the complete discrediting of information. For example, in the opening
paragraphs of Ross et al.’s (1975) seminal article on the belief perseverance effect, the authors
provided examples that specifically involved the partial discrediting of information: a teacher
attributes a student’s disengagement to lack of motivation, but later learns that the student is
undernourished and sleep deprived; a woman infers romantic interest from a man who gives her
flowers, but later learns that the man’s father is a florist. In both of these examples, the new
information partially discredited the foundation upon which the original beliefs were based by
way of offering alternative explanations. The logical response would be for the teacher and the
5
woman to revise their beliefs in a manner commensurate with the degree of discrediting. A
failure to do so would indicate belief perseverance.
Although Ross et al. (1975) recognized that belief perseverance can occur in the context
of partially discredited information, their experiments used the debriefing paradigm as a way to
avoid the complexities created by partially discredited information. However, subsequent to the
publication of their article, a number of studies have examined belief perseverance in the context
of partially discredited information. These studies, which investigated the belief perseverance
effect with a wide-range of topics (e.g., capital punishment, judgments of a suspect’s guilt,
attitudes toward Richard Nixon) underscore the point that belief perseverance occurs under a
broader set of conditions than the debriefing paradigm permits (Carretta & Moreland, 1982;
Marksteiner, Ask, Reinhard, & Granhag 2011; Lord, Ross, & Lepper, 1979).
The Power of Confession Evidence
People’s tendency to show belief perseverance may help to explain the power of
confession evidence. Once a suspect has confessed, people tend to develop an initial expectation
or presumption of guilt (Kassin & Neumann, 1997). Moreover, because of the widespread belief
that innocent suspects would not confess to crimes that they did not commit, it stands to reason
that people would likely hold this initial presumption of guilt quite strongly (Kassin &
Wrightsman, 1981). This is not to say that people necessarily presume innocence in the absence
of a confession, but rather that a confession increases the certainty or strength with which people
presume guilt. Further, even though it is not irrational for a confession to have this effect (a
confession should produce a stronger presumption of guilt than if no confession was present) it
can still have negative consequences for suspects’ outcomes.
6
For example, a confession that is obtained early in a police investigation may cause
detectives to discount subsequently discovered exculpatory evidence more than they would have
had the confession been obtained at the same time or after the exculpatory evidence. High
profile, proven false confession cases illustrate this hypothesized effect. The police and
prosecutor in Jeffrey Deskovic’s case continued to believe in the validity of his confession even
after learning that DNA recovered from the victim excluded him (Leo & Drizin, 2010).
Similarly, the police and prosecutor in the case of the Central Park Five continued to believe in
the validity of the confessions made by the five teenagers accused of the brutal attack and rape of
a jogger in New York City’s Central Park even after discovering that their confessions were
riddled with inconsistencies, did not correspond to witness statements, and that DNA recovered
from the victim did not implicate them (Weiss, Watson, & Cynwyd, 2013).
Although proven false confession cases such as these provide anecdotal evidence that a
confession can lead people to cling to the belief that a suspect is guilty despite the subsequent
discovery of exculpatory evidence, only one study has empirically tested this effect (More,
Madon, Guyll, & Atkinson, 2015). Participants in the study read a crime report across two
phases, rating the suspect’s guilt at each phase. In phase 1, the crime report described
circumstantial evidence that pointed toward the suspect’s guilt. In phase 2, exculpatory evidence
that pointed toward the suspect’s innocence was added. All participants also received confession
evidence, but half of the participants receive it during phase 1, whereas the other half received it
during phase 2. Therefore, all participants ultimately received identical evidence, with the only
variation being when the confession evidence was presented.
The authors hypothesized that participants who received confession evidence before the
exculpatory evidence would be more likely than participants who received it alongside the
7
exculpatory evidence to presume that the suspect was guilty. However, the findings did not
support this hypothesis. Instead, the findings indicated that the timing of the confession evidence
did not influence participants’ judgments of the suspect’s guilt at phase 2. Consideration of the
study’s methods suggests two factors that may have contributed to this non-significant effect.
Ambiguity
One aspect of the study that may have contributed to the non-significant effect was the
nature of the exculpatory evidence. Because More et al. (2015) relied on clearly unambiguous
exculpatory evidence, participants may have had no reason to doubt the suspect’s innocence. A
large literature in psychology indicates that ambiguity increases people’s susceptibility to
cognitive biases (Tversky & Kahneman, 1974). In fact, this is a central thesis of the literature on
error and bias – i.e., that people use heuristics when making probabilistic judgments. Therefore,
it is possible that participants in More et al.’s study might have been more likely to discount the
exculpatory evidence in favor of their initial guilt judgments had it been ambiguous rather than
clearly unambiguous. According to this reasoning, the hypothesized belief perseverance effect
may be more likely when a confession is discredited by ambiguous, rather than clearly
unambiguous, exculpatory evidence.
Commitment
A second aspect of More et al.’s (2015) procedures that may have contributed to the nonsignificant belief perseverance effect is that participants were not particularly motivated to
maintain their initial guilt judgments. This possibility is consistent with a core theme that runs
throughout the psychological literature; namely, that motivational factors influence people’s
beliefs and behaviors. For example, Cialdini (1984) outlined six key principles of social
influence, one of which was the principle of commitment and consistency. According to this
8
principle, a central motive that influences people’s behavior is the need to behave consistently
with their previously established beliefs (Cialdini, 1999). If people commit to a belief or
behavior, then they are more likely to maintain that belief or behavior at a later point in time
(Cialdini, 1984), an effect that has received strong empirical support (Baca-Motes, Brown,
Gneezy, Keenan, & Nelson, 2013; Dickerson, Thibodeau, Aronson, & Miller, 1992).
The principle of commitment and consistency may also be relevant to understanding how
belief perseverance operates in the context of criminal investigations. Due to internal and
external pressures to capture perpetrators and solve crimes, police investigators may be
motivated to maintain their beliefs in a suspect’s guilt after obtaining a confession. Put
differently, after police investigators have obtained a confession from a suspect, they may be
disinclined to revise their judgments about the suspect’s guilt even if they later discover
exculpatory evidence. Therefore, the hypothesized belief perseverance effect may partly depend
on people’s motivation to maintain their initial beliefs, with stronger effects occurring under
conditions of high commitment.
Research Overview and Hypotheses
This research tested two hypotheses. First, it tested the hypothesis that people who
encounter confession evidence before encountering exculpatory evidence are more vulnerable to
belief perseverance than people who encounter confession and exculpatory evidence
simultaneously. Second, it tested whether this predicted effect is moderated by people’s
commitment to their initial beliefs about a suspect’s guilt, with stronger effects occurring among
people who are highly committed. The research tested these hypotheses in the context of an
experiment that manipulated whether participants encountered confession evidence before or at
9
the same time as exculpatory evidence, and whether or not they publicly committed to an initial
judgment of a suspect’s guilt prior to receiving exculpatory evidence.
10
CHAPTER 2. METHOD
Power Analysis
The statistical software G*Power was employed to estimate the appropriate sample size
necessary to detect main effects of confession timing and commitment, plus an interaction effect
involving these variables (Faul, Erdfelder, Lang, & Buchner, 2007). The analysis was conducted
using the conventional power value of 1-b = 0.80 at an alpha level of α = .05 (Cohen, 1992). The
only known previous study examining confession evidence and belief perseverance had nonsignificant results with a moderate effect size, Cohen’s f = .21 (More et al., 2015). Moreover,
studies such as Dickerson et al. (1992) have found a moderate effect of commitment on behavior,
Cohen’s f = .27. With these studies in mind, a moderate effect size, Cohen’s f = .25, was used to
estimate the sample size (Cohen, 1988). Using this estimate, the power analysis indicated that a
sample size of 179 would be required to achieve the desired level of power. The sample size of
the current research exceeded this minimum.
Participants
Participants (N = 250) were Iowa State University students who participated in exchange
for partial fulfillment of a course requirement. Eight participants were excluded for failing two
key attention check questions, and four experimental sessions were terminated due to a computer
malfunction. Therefore, there were 238 participants in the final sample, including 84 men and
154 women between the ages of 18 and 50 with a mean age of 19.46 years. There were 199
European Americans, 10 Asian Americans, 9 Latin Americans, 8 African Americans, 1 Native
American, and 11 participants who identified as multi-ethnic. All participants were native
English speakers. This study was approved by the Institutional Review Board at Iowa State
University (Appendix J).
11
Design
Participants were randomly assigned to a 2 (phase: phase 1 vs. phase 2) × 2 (confession
timing: early vs. late) × 2 (commitment: high vs. low) mixed-model experimental design, with
repeated measures on the factor of phase (see Table 1). Confession timing manipulated whether
participants received confession evidence before (phase 1) or at the same time as (phase 2)
exculpatory evidence. Participants in the confession–early conditions received the confession
evidence before the exculpatory evidence (phase 1), whereas participants in the confession–late
conditions received the confession and exculpatory evidence simultaneously (phase 2).
Commitment manipulated the degree to which participants were motivated to maintain their
phase 1 judgment of a suspect’s guilt. Participants in the high commitment conditions publicly
revealed their phase 1 guilt judgments to the experimenter and signed a form confirming their
judgment immediately after phase 1 and prior to beginning phase 2. Participants in the low
commitment conditions neither publicly revealed nor confirmed their phase 1 guilt judgments
prior to beginning phase 2.
Crime Report
A fictional crime report (see Appendices A, B, and C) described an assault and theft in
which a male assailant struck a woman on the head from behind and stole her purse as she was
entering a car in a parking lot. The victim was unable to describe the perpetrator, and footage
from a surveillance video was too grainy to be useful. Based on the circumstantial evidence,
Kyle James became the prime suspect. During an interrogation, James confessed to the crime,
but later recanted his confession, claiming that he had been at a local restaurant when the crime
occurred. His alibi was supported by a credit card transaction and a questionable eyewitness
identification.
12
Measures
Guilt Judgments
Participants judged the suspect’s guilt by responding to three questions: (1) “Based on the
information presented in the criminal report, if you had to choose, would you say that Kyle
James is more likely to be guilty or innocent?”, with response options 1 (guilty) and 2 (innocent),
(2) “How confident are you in your decision?”, with endpoints 1 (not at all confident) and 10
(very confident), and, (3) “How likely do you think it is that James is guilty?”, with endpoints 1
(very unlikely) and 10 (very likely). Participants responded to these questions twice, once during
phase 1 and then again during phase 2 (see Appendix D). These variables are subsequently
referred to as verdict, confidence, and likelihood of guilt.
Perceptions of Impartiality
Two questions assessed the degree to which participants perceived themselves as having
provided an impartial judgment of the defendant’s guilt: (1) “To what extent was your Assessment
based on the evidence provided within the crime report?”, with endpoints 1 (not at all evidencebased) and 10 (completely evidence-based); and (2) “How impartial was your Assessment of the
case?”, with endpoints 1 (not at all fair and impartial) and 10 (very fair and impartial).
Participants’ responses to these questions were averaged to create one score per participant with
higher scores corresponding to greater levels of perceived impartiality. Participants answered
these questions during phase 2 (see Appendix E).
Manipulation Check
Participants answered five manipulation check questions (see Appendix F). One question
used a multiple-choice format to assess whether participants correctly recalled the confession.
Responses were coded as 1 (correct) and 0 (incorrect). The four remaining manipulation check
13
questions assessed the strength of participants’ commitment to their guilt judgments: (1) “After
you read the crime report for the first time, how strong was your belief that the suspect was
guilty or innocent?”, with endpoints 1 (very weak belief) and 10 (very strong belief), (2) “After
you read the crime report for the first time, how strong would new evidence had to have been for
you to change your verdict from guilty to innocent or innocent to guilt?”, with endpoints 1 (not
very strong) and 10 (very strong), (3) “Thinking about your final verdict in this case, how
difficult would it be for someone to convince you to change your verdict from guilty to innocent
or from innocent to guilty?”, with endpoints 1 (not very difficult) and 10 (very difficult), and (4)
“Thinking about your final verdict in this case, how strong would new evidence have to be for
you to change your verdict from guilty to innocent or innocent to guilty?”, with endpoints 1 (not
very strong) and 10 (very strong). Participants’ responses to these four questions were averaged
to create one score per participant with higher scores indicating greater commitment to their guilt
judgments.
Attention Check
Eight questions assessed the extent to which participants attended to the crime report (see
Appendix G). These questions asked participants to recall the suspect’s name, whether the
suspect confessed to the crime, what the suspect’s alibi was, and the circumstantial evidence that
the police had against the suspect. Responses were coded as 1 (correct) and 0 (incorrect) and
summed to create one score per participant that ranged from 0 to 8, with higher scores indicating
a greater degree of attentiveness to the crime report.
Suspicion Check
Four questions assessed participants’ general level of suspicion, prior knowledge about
the experiment, and the degree to which they perceived the experimenter to be credible (see
14
Appendix H): (1) “Sometimes experiments study questions that are not obvious. Do you believe
that is the case in this experiment?”, with response options 1 (yes) and 2 (no), (2) “If yes, please
indicate what research question(s) might be under investigation in this experiment.” (openended), (3) “Please indicate what you knew about this experiment before participating.” (openended), and (4) “Please rate as honestly as possible how believable you found the experimenter
when he or she informed you that some of the materials had been left out. This question will
remain anonymous and the experimenter will never learn of your rating.”, with endpoints 1
(completely unbelievable) and 6 (completely believable). Responses were evaluated to identify
participants who identified the research hypotheses, had prior knowledge of the experimenter, or
were suspicious about the feigned experimental mistake.
Scrambled Anagrams
As a filler task, all participants attempted to solve up to 44 scrambled anagrams within
four minutes (see Appendix I). Pilot testing showed that college students can complete an
average of 20 anagrams in this timeframe, with a minimum and maximum of 9 and 32,
respectively. The filler task was included to provide a window of time that supported a feigned
claim by the experimenter that a portion of the crime report had accidentally been omitted from
the materials, thus necessitating that they receive the full crime report and respond to the
questions a second time. Because the scrambled anagram task is unrelated to the hypotheses
under investigation, it was not scored or used in any of the analyses.
Procedures
Participants were run individually. Upon arrival to the experimental session, the
participant signed a consent form and was told that the study was designed to examine how
people evaluate evidence in a criminal case. The experimenter then explained that the participant
15
would review evidence from a real, ongoing case after which the participant received a portion of
a crime report that included circumstantial evidence (phase 1). This portion of the crime report
also included confession evidence for participants in the confession–early conditions. After
reading this portion of the crime report, the participant made several guilt-relevant judgments
including a verdict (guilty vs. innocent), confidence rating, and likelihood of guilt judgment. The
commitment manipulation occurred immediately after.
In the high commitment conditions, the participant publicly stated his or her phase 1
verdict (guilty vs. innocent) and signed a form confirming it. Participants performed these tasks
believing that the signed form would be sent to the county prosecutor’s office to help with the
case. To support the veracity of this claim, the experimenter placed the participant’s signed form
in an envelope addressed to the county prosecutor’s office and left the room under the guise of
depositing it in the mail. In the low commitment conditions, the participant did not publicly state
his or her phase 1 verdict, nor sign any form to confirm it.
Following the commitment manipulation, the participant was left alone to work on the
filler task for four minutes. Afterward, the experimenter informed the participant that during the
filler task, she or he had discovered that a portion of the crime report had accidentally been
omitted, thus necessitating that the participant read the full crime report and answer the questions
a second time. After having done so, the participant responded to the manipulation checks,
attention checks, suspicion checks, and reported demographic information. After all measures
had been completed, the experimenter fully debriefed the participant.
16
CHAPTER 3. ANALYSES
Preliminary Analyses
Descriptive Statistics
Table 2 presents the means, standard errors, and confidence intervals for participants’
verdicts, confidence ratings, and likelihood of guilt judgments organized by experimental
condition. Table 3 presents the correlations between variables for the entire sample whereas
Table 4 presents the correlations separately for participants in the low commitment and high
commitment conditions. Figure 1 presents participants’ verdicts, which are shown by condition
and phase as they proceeded through the study.
Commitment Manipulation Check
An independent samples t-test assessed the effectiveness of the commitment
manipulation. Results indicated no significant difference in self-reported commitment levels
between participants in the low commitment and high commitment conditions, t (236) = 0.80, p
= .427, d = .10. Note that d values of .2, .5, and .8 correspond to small, medium, and large
effects, respectively (Cohen, 1988). These results suggest either that the commitment
manipulation was unsuccessful or that the self-report questionnaire failed to properly assess
participants’ commitment levels.
Confession Timing Manipulation Check
A frequency analysis indicated that 210 participants (88.2%) correctly identified whether
the confession was presented during phase 1 or phase 2, whereas 28 (11.8%) incorrectly reported
its timing. A series of independent samples t-tests that compared participants who correctly and
incorrectly answered the confession timing manipulation check question revealed no significant
differences in their phase 2 likelihood of guilt judgments, t (236) = -0.55, p = .586, d = .11, or
17
phase 2 verdicts, t (236) = 0.13, p = .901, d = .02. These results suggest that there were no
meaningful differences between participants who correctly identified the timing of the
confession evidence and those who did not. Accordingly, no participants were excluded on the
basis of their answer to the timing of the confession evidence.
Attention Check
A frequency analysis identified participants who had not adequately attended to the crime
report according to the following a priori decision criterion (a) incorrectly answered six or more
of the eight attention check questions, (b) incorrectly reported the suspect’s name or (c)
incorrectly reported that the suspect never confessed. Eight participants were identified.
Although all subsequently reported results omitted these participants’ data the analyses were
conducted both with and without these participant’s data included, and no meaningful
differences emerged.
Suspicion Check
Assessment of participants’ responses to the suspicion check items indicated that none
were suspicious and none correctly identified the study hypotheses.
Analytic Plan
The main analyses address the hypotheses that confession timing influences phase 2 guilt
judgments by means of belief perseverance, and that commitment moderates the hypothesized
belief perseverance effect. These hypotheses are tested with respect to two measures of
participants’ guilt judgments: phase 2 likelihood of guilt judgments and verdicts (guilty vs.
innocent). As discussed in detail below, support for belief perseverance in these data requires
that two effects be significant – i.e., confession timing must have a significant total effect on
participants’ phase 2 guilt judgments and a significant indirect effect on participants’ phase 2
18
guilt judgments through participants’ phase 1 guilt judgments. These effects were tested with the
following, closely related sequential models.
Model 1: Total Effect of Confession Timing on Phase 2 Guilt Judgments
The first model (Figure 2) was designed to test whether confession timing had a
significant total effect on phase 2 guilt judgments, with a greater perceived likelihood of guilt
and a greater likelihood of guilty verdicts expected among participants in the confession–early
conditions. This effect reflects a necessary, but insufficient, condition to conclude that belief
perseverance had a meaningful impact on phase 2 guilt judgments. It is necessary because it is
only possible that belief perseverance had a meaningful impact if confession timing had an effect
on participants’ phase 2 guilt judgments. However, it is insufficient because the total effect of
confession timing captures not only the belief perseverance effect, but also additional effects
linked to the experimental procedures, as subsequently detailed. Hence, the second model is
needed to parse the total effect of confession timing and isolate that portion associated with
belief perseverance.
It is worth noting that, in general, a significant total effect is not necessary to find a
mediation effect. However, for the purposes of this research, a significant total effect of
confession timing is necessary as a lack of such an effect would suggest that guilt judgments do
not vary depending on when confession evidence is encountered. Therefore, a significant indirect
effect would be of little consequence if final guilt judgments are not impacted in a meaningful
way as evidenced by a significant total effect.
The first model would support the belief perseverance hypothesis if confession timing
evidenced either a significant main effect on phase 2 guilt judgments or a significant simple main
effect on phase 2 guilt judgments in the context of an interaction involving commitment, or both.
19
For the continuous guilt judgment of likelihood of guilt, a 2 × 2 (confession timing
× commitment) regression analysis was performed. For the dichotomous guilt judgment of
verdict, a 2 × 2 (confession timing × commitment) logistic regression was performed. For both
analyses, the experimental manipulations of confession timing (late vs. early) and commitment
(low vs. high) were effect-coded as -1 and +1, respectively. If confession timing demonstrates
either a significant main effect, or a significant simple main effect, then a second, more detailed
path model becomes necessary.
Model 2: Belief Perseverance Effect
The second model was designed to test whether a significant total effect of confession
timing on phase 2 guilt judgments revealed by the prior model corresponded to belief
perseverance (see Figure 3). This was accomplished by examining whether confession timing
evidenced a significant indirect effect on phase 2 guilt judgments through phase 1 guilt
judgments. The model tests this indirect effect with the Mplus statistical program (Mplus, 2018).
If the first model yields a simple main effect of confession timing on phase 2 guilt judgments in
the context of an interaction with commitment, then the second model tests the indirect effect
separately for each level of commitment. Therefore, the variable corresponding to the
experimental manipulation of commitment is held constant in each group, requiring removal of
the two terms involving commitment and their corresponding paths, d and e in Figure 3.
Regardless of these effects related to commitment, the paths a, b, and c are included, and their
meanings in the context of the path model merit detailed consideration.
Path a: Confession Effect
Participants made guilt judgments twice, first at phase 1 and then again at phase 2. As
shown in Table 1, because the commitment manipulation did not occur until after participants
20
made their phase 1 guilt judgments, the only difference between the confession timing conditions
at phase 1 was the presence or absence of the confession; at phase 1, the confession was present
for participants in the confession–early conditions and absent for participants in the confession–
late conditions. Therefore, path a in Figure 3 reflects the effect of confession evidence on
phase 1 guilt judgments above and beyond the effect of the circumstantial evidence presented at
phase 1.
Path b: Judgment Stability
Path b in Figure 3 represents the stability of guilt judgments from phase 1 to phase 2.
Path a × b: Belief Perseverance
By definition, the phenomenon of belief perseverance requires that people maintain their
initial beliefs in the face of subsequently encountered discrediting information. In the current
study, this means that differences in guilt judgments at phase 2 between participants in the
confession–early and confession–late conditions must be conveyed by differences in their
preceding guilt judgments at phase 1. In terms of the model shown in Figure 3, this corresponds
to a significant indirect effect of confession timing on phase 2 guilt judgments via phase 1 guilt
judgments (a × b). At this point it is worth restating that this effect only indicates belief
perseverance if confession timing also evidenced a significant total effect on phase 2 guilt
judgments in the corresponding 2 × 2 analysis previously described. In the absence of a total
effect, a significant indirect effect indicates that the information added in phase 2 (exculpatory
and circumstantial, as detailed in Table 1) counteracted any effect of the confession evidence on
phase 2 guilt judgments, as described next.
Path c: Adding Confession Evidence and Procedural Effects
To understand the direct effect of the confession timing manipulation on phase 2 guilt
21
judgments represented by path c it is necessary to understand the differences that exist between
the confession timing conditions at the time phase 2 guilt judgments were made. As detailed in
Table 1, at the time phase 2 guilt judgments are made, the two confession timing conditions were
identical with respect to the information they had received. However, the effect represented by
path c is unique of the indirect effect of the confession itself on phase 2 guilt judgments,
represented by path a × b. Thus, path c captures the effect of adding the confession in the
confession–late condition, thereby causing the total effect of confession timing on phase 2 guilt
judgments, path a × b + c, to reflect the fact that both conditions have precisely the same
information at phase 2.
Path c also captures three other condition differences associated with confession timing
that operate at phase 2 but not phase 1, none of which reflect belief perseverance. First, it
captures any primacy or recency effects associated with participants in the confession–early
conditions having received the confession earlier than participants in the confession–late
condition. Second, it captures any pairing effects caused by the fact that participants in the
confession–early conditions received the confession without the simultaneous presentation of
exculpatory evidence, whereas participants in the confession–late conditions received the
confession simultaneously with the exculpatory evidence. Third, it captures any effects of
information quantity that resulted from participants in the confession–early conditions having
received the confession in the context of less additional information (only the circumstantial 1
evidence, as detailed in Table 1) compared to participants in the confession–late conditions who
received the confession in the context of more additional information (both the circumstantial 2
and the exculpatory evidence, as detailed in Table 1). Thus, path c includes the potential
influence of several procedural effects possibly associated with the confession timing
22
manipulation, and thereby separates them from the belief perseverance effect represented by the
indirect effect, path a × b.
Moderation of Belief Perseverance by Commitment
The analytic plan described above also enables Assessment of commitment’s ability to
moderate belief perseverance. Results consistent with moderation would include a significant
interaction of commitment and confession timing on phase 2 guilt judgments in the 2 × 2 model,
coupled with significant belief perseverance effects in the follow up path model that differ across
levels of commitment.
Main Analyses
The main analyses tested two hypotheses pertaining to the effects of confession timing
and commitment on phase 2 guilt judgments. The first hypothesis was that the confession would
have a stronger effect on phase 2 guilt judgments among participants in the confession–early
than confession–late conditions. The second hypothesis was that the predicted effect of
confession timing would be stronger among participants in the high than low commitment
conditions. As noted above, these hypotheses were tested with respect to participants’
perceptions of the suspect’s likelihood of guilt and verdicts of guilty versus innocent.
Model 1: Total Effect of Confession Timing
Following the analytic plan described above, the first set of analyses tested whether
confession timing had a significant total effect on phase 2 guilt judgments. First, a 2 × 2
(confession timing × commitment) regression analysis was performed using the phase 2
continuous guilt judgment of likelihood of guilt as the dependent variable. Results indicated that
confession timing was not a significant predictor of phase 2 guilt judgments, b = .103, t (234) =
0.91, p = .365, d = .12. Conversely, commitment was a significant predictor of phase 2 guilt
23
judgments, b = -.330, t (234) = -2.90, p = .004, d = -.38. The negative beta weight of the
commitment predictor indicates that participants in the low commitment conditions were more
likely to have a stronger likelihood of guilt belief than participants in the high commitment
conditions. The interaction term for the two predictors was not significant, b = -.059, t (234) = –
0.52, p = .607, d = -.07.
Paralleling the regression analysis, a 2 × 2 (confession timing × commitment) logistic
regression analysis was performed using the phase 2 dichotomous guilt judgment of verdict as
the dependent variable. Results revealed that confession timing did not have a significant effect
on phase 2 verdicts, b = .144, Wald χ² (1) =1.02, p = .313, OR = 1.15. Note that odds ratios of
1.5, 2.5, and 4.3 correspond to small, medium, and large effects, respectively (Cohen, 1988).
Conversely, commitment, b = -.272, Wald χ² (1) = 3.65, p = .056, OR = 0.76, and the confession
timing by commitment interaction, b = -.275, Wald χ² (1) = 3.71, p = .054, OR = 0.76, had
marginally significant effects on phase 2 verdicts.
A follow-up analysis was conducted to examine the simple main effects of confession
timing. Pairwise comparisons indicated that confession timing had no significant effect on
verdicts in the high commitment conditions, t (120) = -0.70, p = .482, OR = 0.79. Confession
timing did have a significant effect on verdicts in the low commitment conditions, t (114) = 2.00,
p = .045, OR = 1.96, with participants in the confession–early condition more often finding the
suspect guilty than participants in the confession–late condition. Thus, belief perseverance could
not have occurred under conditions of high commitment, but may have occurred under
conditions of low commitment.
Model 2: Belief Perseverance Effect
As described in the analytic plan, the second model was designed to test whether
24
significant results associated with confession timing from the first model corresponded to belief
perseverance. This was accomplished by examining whether confession timing had a significant
indirect effect on phase 2 guilt judgments through phase 1 guilt judgments using the analytic
model depicted in Figure 3. The first model showed that belief perseverance was only a
possibility for the dichotomous verdict dependent variable, and only for the low commitment
condition. Therefore, the second model tested for indirect effects of confession timing on the
dichotomous guilt judgment of verdict, doing so separately for each level of commitment.
Specifically, the analysis was conducted using the model depicted in Figure 3 that included only
paths a, b, and c, and was performed using MPlus with commitment as the grouping variable.
Due to the nonsignificant findings in the high commitment conditions, only results from the low
commitment conditions are relevant to the belief perseverance hypothesis. Therefore, only the
results for participants in the low commitment conditions will be presented. However, for
completeness all high commitment results are presented in Table 5.
Path a: Confession Effect
For participants in the low commitment conditions, results revealed that confession
timing had a significant direct effect on phase 1 verdicts (path a), b = .48, SE = 0.14, p < .01, OR
= 1.62. As previously noted, path a in Figure 3 represents the effect of confession on phase 1
guilt judgments beyond the impact of the circumstantial evidence presented at phase 1.
Therefore, the results for path a indicate that the presence of confession evidence significantly
influenced verdicts.
Path b: Judgment Stability
For participants in the low commitment conditions, results showed that phase 1 verdicts
significantly predicted phase 2 verdicts (path b), b = .64, SE = 0.12, p < .01, OR = 1.90.
25
Recalling that path b in Figure 3 represents the stability of guilt judgments from phase 1 to phase
2, the results indicate that verdicts evidenced a degree of stability from phase 1 to phase 2.
Path a x b: Belief Perseverance
For participants in the low commitment conditions, results revealed that confession
timing had a significant indirect effect on phase 2 verdicts via phase 1 verdicts (path a × b), b =
.31, SE = 0.10, p < .01, OR = 1.36. Although there was a significant indirect effect of confession
timing, it is worth restating that this effect only represents belief perseverance because
confession timing also evidenced a significant total effect on phase 2 verdicts, as reported above
for Model 1 with respect to the simple main effect results of confession timing on phase 2
verdicts in the low commitment conditions.
Path c: Adding Confession Evidence and Procedural Effects
For participants in the low commitment conditions, results revealed that confession
timing had a non-significant direct effect on phase 2 verdicts (path c), b = -.06, SE = .13, p = ns,
OR = 0.94. However, as previously noted in the analytic plan, path c captures several condition
differences associated with confession timing that operate at phase 2 but not phase 1, none of
which reflect belief perseverance.
Path a x b + c: Total Effect of Confession Evidence
For participants in the low commitment conditions, results showed that confession timing
had a significant total effect on phase 2 verdicts (path a × b + c), b = .25, SE = 0.13, p < .05, OR
= 1.28. This result replicates the simple main effect of confession timing in the low commitment
conditions from Model 1. Moreover, the presence of the aforementioned significant indirect
effect and a significant total effect indicates support for a belief perseverance effect for
participants in the low commitment conditions. Specifically, this indicates that participants who
26
received confession evidence early at phase 1 had a greater likelihood of providing a guilty
verdict at phase 2 with a significant portion of this effect resulting from the perseverance of
participants’ phase 1 verdicts.
Moderation of Belief Perseverance by Commitment
As noted above, the analytic plan allowed for the Assessment of commitment’s ability to
moderate belief perseverance. Results were consistent with a moderation effect. A marginally
significant interaction between confession timing and commitment on phase 2 verdicts was
found in the first model. Moreover, in the follow-up path model, the results supported a belief
perseverance effect for participants in the low commitment conditions. Taken together these
results suggest that belief perseverance was greater when commitment to an initial verdict was
low.
27
CHAPTER 4. DISCUSSION
Drawing on research relevant to the cognitive bias of belief perseverance, this research
tested whether a confession causes people to discount subsequently encountered exculpatory
evidence, and whether this effect is stronger when people are highly committed to maintaining
their initial beliefs about a suspect’s guilt. Results provided some support for the presence of a
belief perseverance effect. However, belief perseverance only occurred under low commitment
conditions and not under high commitment conditions, as had been originally hypothesized. In
addition, a main effect of commitment emerged such that participants who were committed to
their initial beliefs about a suspect’s guilt were more likely than those who were less committed
to adjust their initial verdicts in response to exculpatory evidence, a pattern that runs counter to
the hypothesized moderating effect of commitment.
Belief Perseverance
Although the timing of confession evidence did not have an overall effect on verdicts, it
did evidence a simple main effect on verdicts among participants in the low commitment
conditions. Specifically, participants in the low commitment conditions who received confession
evidence before receiving exculpatory evidence were more likely to find the suspect guilty than
participants who received confession and exculpatory evidence at the same time. It is worth
noting that this pattern was only present with verdict judgments and not with likelihood of guilt
judgments. However, this discrepancy may be due to the fact that the commitment manipulation
was implemented in an attempt to make participants feel committed to their verdicts. Participants
were encouraged, in the high commitment conditions, to become committed to their initial
verdicts by having participants verbally state and sign a form affirming them. By contrast, no
such attempt was ever made to make any participants adhere to their original likelihood of guilt
28
judgments. Therefore, the commitment manipulation may have been experienced as most
relevant with respect to verdicts, and rather less so with respect to likelihood of guilt judgments.
The lack of a main effect for the timing of the confession evidence in these data may
suggest that the intensity of the manipulation was insufficient. For the purposes of this study,
participants received the first portion of the crime report and then completed a four-minute filler
task before receiving the full crime report. Considering that investigators often have weeks or
even months to ruminate about a given case before possibly receiving exculpatory evidence, this
may not have been an adequate amount of time for strong beliefs to develop. The lack of a strong
initial belief may have discouraged participants from discounting the subsequently encountered
exculpatory evidence.
An alternative explanation that may explain why the timing of the confession did not
have a significant main effect on guilt judgments is that the procedures used in this study did not
closely mimic the processes of police investigators. In fact, they were more similar to the
processes of jurors. Participants in this study were presented with incriminating evidence
followed by exculpatory evidence and then asked to make a guilt judgment. This presentation of
evidence mirrors that which jurors experience in trials. In court proceedings the prosecution first
offers incriminating evidence for the jurors to consider before the defense has the opportunity to
provide exculpatory evidence. Moreover, participants in this study did not seek out information
or spend weeks investigating and building a strong belief. Further, participants, like jurors, may
be motivated to be accurate whereas police investigators may be motivated to avoid being
perceived as fallible. Therefore, the results of this study may have failed at assessing how police
investigators make judgments, but succeeded at examining the decision making processes of
jurors.
29
Commitment
Although only an interaction with confession timing had been predicted, commitment
also had a significant main effect on guilt judgments. Participants in the high commitment
conditions gave lower guilt judgments than participants in the low commitment conditions. Thus,
commitment had a clear effect, which indicates that the lack of support for what had been
hypothesized was not due to a failed manipulation. Additionally, suspicion checks indicated low
levels of suspicion and no participants correctly identified the study hypotheses, which indicates
that the results were not due to psychological reactance.
Accountability
Based on anecdotal evidence from proven false confession cases and the empirical
literature on commitment, it was hypothesized that the predicted belief perseverance effect
would be moderated by people’s commitment to their initial beliefs about a suspect’s guilt, with
stronger effects occurring among people who are highly committed. However, the results showed
the opposite effect. This raises the possibility that perhaps the experimental manipulation did not
manipulate commitment after all, but instead accountability – an expectation of having to justify
or explain one’s feelings, beliefs, or behaviors to others (Lerner & Tetlock, 1999). Participants in
the high commitment conditions were asked to verbally state and sign a document affirming their
guilt judgments that they believed were being sent to the county prosecutor in an attempt to
impress upon them that their decisions were meaningful. Therefore, participants may have been
more analytical in their assessments as research has found that holding people accountable for
their judgments and decisions leads them to think in more critical and complex ways such that
they are more likely to consider multiple perspectives on the issue at hand (Tetlock, 1983a;
Tetlock, 1983b).
30
Research has long established that the innate need to appear consistent in terms of one’s
beliefs and attitudes is a fundamental basis of behavior (Festinger, 1957). Most people strive for
consistency in terms of what they say and do. Therefore, after committing to a given opinion,
especially when that opinion is freely chosen, people are likely to continue to behave in a manner
that is in line with their original position (Cialdini, 1999). However, if the commitment
manipulation used in the current study inadvertently manipulated accountability, then
participants in the high commitment conditions may have more thoroughly assessed the
exculpatory evidence and been more likely to entertain the possibility that the suspect was
actually innocent despite his confession than participants in the low commitment conditions out
of an increased desire to be accurate. To the extent this happened, then a conservative criterion
shift may have occurred among participants in the high commitment conditions. That is,
participants in the high commitment conditions may have required a greater degree of certainty
in the suspect’s guilt before being willing to render a guilty verdict. Consistent with this,
preliminary analyses showed that participants in the high commitment conditions reported being
less confident in their phase 2 verdicts than participants in the low commitment conditions.
Limitations
Several limitations of this research warrant mention. First, the participant sample
consisted entirely of college students. Although this limitation characterizes many empirical
studies, it has meaningful repercussions for the current research. Due to the relative youth of the
sample and their enrollment in a secondary education institute, it is possible that they have
greater cognitive flexibility than other populations. Had the sample consisted of a more
heterogeneous sample, or even a sample of older adults, participants may have shown a greater
tendency to cling to their initial beliefs.
31
Second, although this study attempted to manipulate commitment, the procedures may
not have been especially well-suited to capturing an investigator’s sense of responsibility and
desire to find justice; participants did not have much personally riding on their guilt judgments.
However, this also means that the results are likely a conservative estimate of the possible effects
of the timing of confession evidence and commitment on guilt judgments of actual investigators.
Relatedly, given that this study relied on the judgments of college students rather police
investigators, the results may say more about the way that jurors assess evidence than the way
that investigators do.
Finally, the commitment manipulation may have inadvertently manipulated
accountability, possibly explaining the presence of belief perseverance in the low, but not the
high commitment conditions. A key aspect of commitment in previous studies involves the
desire to appear consistent and also to avoid appearing hypocritical. For example, in Dickerson et
al.’s (1992) study, participants who signed a flyer in support of water conservation took
significantly shorter showers. An individual who signs a flyer supporting the conservation of
water and then proceeds to shower for half an hour is behaving in an inconsistent manner and
would appear to be a hypocrite. However, in the current study, participants were able to assign a
verdict of guilty and then switch to innocent without appearing hypocritical due to the nature of
the evidence presented. Therefore, future studies should attempt to create situations wherein
participants are motivated to maintain consistency, such as if changing one’s mind would be
viewed as an admission of incompetence.
Conclusion
The present study applied theory from the literature on error and bias in an attempt to
understand the impact of confession evidence on an individual’s guilt judgments. Although this
32
study failed to find an overall belief perseverance effect, it did find such an effect for participants
who were not made to feel committed to (or accountable for) their initial guilt belief.
Additionally, it was found that commitment had a meaningful impact on guilt judgments such
that those participants who were made to feel committed to (or accountable for) their initial guilt
judgments gave lower final guilt judgments. Future studies should examine whether these
procedures truly lead participants to feel committed to their beliefs or instead lead to a greater
sense of accountability, which then creates a conservative criterion shift in their guilt judgment
decisions such that they require a greater degree of certainty of guilt to offer a guilty verdict.
Moreover, future research should attempt to include people who are more invested in the
decisions by, if possible, recruiting participants from law enforcement.
33
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37
Figure 1. Participants’ verdicts by condition and phase as they proceeded through the study.
38
Figure 2. Model examining the total effect of confession timing, commitment, and the
confession timing by commitment interaction on phase 2 guilt judgments.
39
Figure 3. Mediated model examining the effect of phase 1 guilt judgments, confession timing,
commitment, and the confession timing by commitment interaction on phase 2 guilt judgments.
40
Table 1
Experimental Design: Confession x Commitment x Phase
Commitment Confession
Timing
Phase 1
Crime Report
Phase 2
Crime Report
High Early Circumstantial 1 + Confession add Circumstantial 2 +
Exculpatory
Late Circumstantial 1 add Circumstantial 2 +
Confession + Exculpatory
Low Early Circumstantial 1 + Confession add Circumstantial 2 +
Exculpatory
Late Circumstantial 1 add Circumstantial 2 +
Confession + Exculpatory
41
Table 2
Descriptive Data for Dependent Variables by Experimental Condition (N = 238)
Variable
Commitment Low Commitment High
Confession
Early
Confession
Late
Confession
Early
Confession
Late
Phase 1 Verdict
M (SE) 88% (4%) 58% (7%) 82% (5%) 58% (6%)
95% CI 79%, 97% 45%, 71% 72%, 92% 45%, 71%
Phase 1 Confidence
M (SE) 7.77 (.24) 6.03 (.23) 7.68 (.22) 5.60 (.20)
95% CI 7.29, 8.25 5.58, 6.49 7.25, 8.12 5.19, 6.00
Phase 1 Likelihood
of Guilt Judgment
M (SE) 7.81 (.24) 5.85 (.21) 7.58 (.26) 5.76 (.21)
95% CI 7.33, 8.29 5.43, 6.26 7.07, 8.10 5.33, 6.19
Phase 2 Verdict
M (SE) 81% (5%) 64% (6%) 58% (6%) 65% (6%)
95% CI 70%, 91% 52%, 77% 45%, 71% 52%, 77%
Phase 2 Confidence
M (SE) 6.72 (.19) 6.49 (.21) 6.28 (.21) 5.97 (.23)
95% CI 6.34, 7.10 6.07, 6.91 5.86, 6.70 5.50, 6.43
Phase 2 Likelihood
of Guilt Judgment
M (SE) 6.54 (.22) 6.22 (.24) 5.77 (.25) 5.68 (.20)
95% CI 6.10, 6.98 5.74, 6.70 5.27, 6.26 5.27, 6.08
Incriminatinga
M (SE) 6.36 (.25) 5.89 (.26) 5.92 (.22) 5.68 (.25)
95% CI 5.86, 6.85 5.36, 6.41 5.47, 6.37 5.18, 6.18
Exoneratingb
M (SE) 4.80 (.18) 5.29 (.21) 5.34 (.21) 5.40 (.19)
95% CI 4.44, 5.15 4.88, 5.70 4.92, 5.76 5.02, 5.79 a
Incriminating = Perceived strength of the incriminating evidence.
b
Exonerating = Perceived strength of the exonerating evidence.
42
Table 3
Correlations (N = 238)
Variable 1 2 3 4 5 6 7 8
1. Confession Timing – .00 .30** .49** .47** .05 .08 .06
2. Commitment – -.03 -.07 -.04 -.12 -.15* -.19*
3. Phase 1 Verdict – .35** .67** .40** .16* .32**
4. Phase 2 Confidence – .59** .31** .45** .32**
5. Guilt 1a – .31** .20** .43**
6. Phase 2 Verdict – .37** .69**
7. Phase 2 Confidence – .46**
8. Guilt 2b –
M -.02 .03 .71 6.75 6.73 .67 6.36 6.04
SD 1.00 1.00 .46 1.96 2.01 .47 1.65 1.78
Note. Confession Timing coded as: Confession Early = 1; Confession Late = -1.
Commitment coded as: Commitment High = 1; Commitment Low = -1. Phase 1 Verdict and
Phase 2 Verdict coded as: Innocent = 0; Guilty = 1. a
Guilt 1 = Phase 1 Likelihood of Guilt Judgment.
b
Guilt 2 = Phase 2 Likelihood of Guilt Judgment.
* p < .05. ** p < .01.
43
Table 4
Correlations by Commitment Low (N = 116) and Commitment High (N = 122) Conditions
Variable 1 2 3 4 5 6 7
Commitment Low
1. Confession Timing – .34** .44** .50** .18 .08 .09
2. Phase 1 Verdict – .29** .65** .44** .23* .33**
3. Phase 2 Confidence – .54** .47** .51** .32**
4. Guilt 1a – .36** .24** .45**
5. Phase 2 Verdict – .47** .67**
6. Phase 2 Confidence – .54**
7. Guilt 2b –
M -.02 .72 6.89 6.81 .72 6.60 6.38
SD 1.00 .45 1.98 1.96 .45 1.53 1.76
Commitment High
1. Confession Timing – .26** .54** .45** -.06 .09 .03
2. Phase 1 Verdict – .40** .69** .36** .10 .32**
3. Phase 2 Confidence – .63** .17 .39** .31**
4. Guilt 1a – .26** .15 .41**
5. Phase 2 Verdict – .27** .70**
6. Phase 2 Confidence – .37**
7. Guilt 2b –
M -.02 .70 6.62 6.66 .61 6.12 5.72
SD 1.00 .46 1.95 2.06 .49 1.73 1.75
Note. Confession Timing coded as: Confession Early = 1; Confession Late = -1.
Phase 1 Verdict and Phase 2 Verdict coded as: Innocent = 0; Guilty = 1. a
Guilt 1 = Phase 1 Likelihood of Guilt Judgment.
b
Guilt 2 = Phase 2 Likelihood of Guilt Judgment.
* p < .05. ** p < .01.
44
Table 5
Direct, Indirect, and Total Effects of Confession Timing on Phase 2 Guilt Verdicts
Path Variable b 95% CI pa OR
Commitment Low
a Confession Timing on Verdict 1 .484 .217, .775 < .01 1.62
b Verdict 1 on Verdict 2 .643 .356, .834 < .01 1.90
c Confession Timing on Verdict 2 -.062 -.313, 202 ns 0.94
a x b Indirect Effect of Confession Timing .311 .147, .534 < .01 1.36
a x b + c Total Effect of Confession Timing .249 .003, .516 < .05 1.28
Commitment High
a Confession Timing on Verdict 1 .350 .106, .612 < .01 1.42
b Verdict 1 on Verdict 2 .637 .386, .814 < .01 1.89
c Confession Timing on Verdict 2 -.304 -.524, -.088 < .01 0.74
a x b Indirect Effect of Confession Timing .223 .082, .404 < .01 1.25
a x b + c Total Effect of Confession Timing -.081 -.310, .162 ns 0.92
Note. Paths correspond to those depicted in Figure 3. CI, confidence interval. a
Effects tested through bias-corrected bootstrapping procedure which precludes calculation of
exact p values.
“ns” corresponds to p > .05.
45
APPENDIX A. PHASE 1 CRIME REPORT: CONFESSION EARLY
On November 15, 2014, just past 8:45pm, a purse was stolen from a woman as she
attempted to enter her 2007 Honda Civic inside a local parking garage. Video surveillance
showed the perpetrator smoking a cigarette before hitting the woman in the back of the head and
taking her purse. The victim never saw the perpetrator’s face and film taken from within the
parking garage was inconclusive due to the poor quality of the video, which made the
perpetrator’s face too blurry to identify. Based on the video footage, police could only determine
that the perpetrator was male, in his late teens or early twenties, had dark hair, light-to-medium
toned skin, and wore blue jeans and a dark colored jacket.
Police searched the nearby area and found a purse in an apartment complex garbage
dumpster located approximately three blocks from the parking garage. The purse was returned to
the victim who identified it as hers and informed the police that all the contents were accounted
for except for approximately $75 in cash that was now missing. After confirming it was the
victim’s purse, police went door-to-door in the apartment complex before eventually finding 24-
year-old Kyle James. James, a Caucasian with a thin, shortcut beard, was found in his home
alone wearing blue jeans and a white t-shirt. A heavy dark blue rain coat was found draped
across the back of his couch. James’ coat contained a pack of cigarettes and his wallet, which
was found to have $83 in it. After finding James and noting that he fit the description of the
perpetrator, police brought him in for questioning.
46
At the police station, officers brought James to an interrogation room to question him.
James waived his Miranda rights and agreed to speak freely with the investigators. During
questioning, James came across to the officers as equal parts defiant and annoyed. After
approximately two hours of questioning, police offered James coffee and a cigarette and allowed
him to use the restroom. After he had rested, investigators returned to questioning him. James
consistently denied any wrongdoing, so the officers reminded him that they had footage of the
crime.
James accused investigators of being incompetent and continued to proclaim his
innocence. The officers countered by playing the tape of the crime and pointing out that he was
wearing blue jeans and a dark coat just like the perpetrator. Investigators also reminded James
that, like the perpetrator in the video, he is a smoker and he was found with just over $80 in his
wallet right after $75 was reported missing. Officers continued to question James over the course
of the next two hours. During this time, the officers again reminded James of the evidence they
had against him at which point James confessed to the crime. He told the police that he was
smoking a cigarette while walking by a woman in the parking garage and saw her purse. He told
of how he hit her in the back of the head and then fled the scene on foot after grabbing the purse.
After verbally confessing, investigators had James write out his confession by hand and sign it.
47
APPENDIX B. PHASE 1 CRIME REPORT: CONFESSION LATE
On November 15, 2014, just past 8:45pm, a purse was stolen from a woman as she
attempted to enter her 2007 Honda Civic inside a local parking garage. Video surveillance
showed the perpetrator smoking a cigarette before hitting the woman in the back of the head and
taking her purse. The victim never saw the perpetrator’s face and film taken from within the
parking garage was inconclusive due to the poor quality of the video, which made the
perpetrator’s face too blurry to identify. Based on the video footage, police could only determine
that the perpetrator was male, in his late teens or early twenties, had dark hair, light-to-medium
toned skin, and wore blue jeans and a dark colored jacket.
Police searched the nearby area and found a purse in an apartment complex garbage
dumpster located approximately three blocks from the parking garage. The purse was returned to
the victim who identified it as hers and informed the police that all the contents were accounted
for except for approximately $75 in cash that was now missing. After confirming it was the
victim’s purse, police went door-to-door in the apartment complex before eventually finding 24-
year-old Kyle James. James, a Caucasian with a thin, shortcut beard, was found in his home
alone wearing blue jeans and a white t-shirt. A heavy dark blue rain coat was found draped
across the back of his couch. James’ coat contained a pack of cigarettes and his wallet, which
was found to have $83 in it. After finding James and noting that he fit the description of the
perpetrator, police brought him in for questioning.
48
APPENDIX C. PHASE 2 CRIME REPORT
On November 15, 2014, just past 8:45pm, a purse was stolen from a woman as she
attempted to enter her 2007 Honda Civic inside a local parking garage. Video surveillance
showed the perpetrator smoking a cigarette before hitting the woman in the back of the head and
taking her purse. The victim never saw the perpetrator’s face and film taken from within the
parking garage was inconclusive due to the poor quality of the video, which made the
perpetrator’s face too blurry to identify. Based on the video footage, police could only determine
that the perpetrator was male, in his late teens or early twenties, had dark hair, light-to-medium
toned skin, and wore blue jeans and a dark colored jacket.
Police searched the nearby area and found a purse in an apartment complex garbage
dumpster located approximately three blocks from the parking garage. The purse was returned to
the victim who identified it as hers and informed the police that all the contents were accounted
for except for approximately $75 in cash that was now missing. After confirming it was the
victim’s purse, police went door-to-door in the apartment complex before eventually finding 24-
year-old Kyle James. James, a Caucasian with a thin, shortcut beard, was found in his home
alone wearing blue jeans and a white t-shirt. A heavy dark blue rain coat was found draped
across the back of his couch. James’ coat contained a pack of cigarettes and his wallet, which
was found to have $83 in it. After finding James and noting that he fit the description of the
perpetrator, police brought him in for questioning.
49
At the police station, officers brought James to an interrogation room to question him.
James waived his Miranda rights and agreed to speak freely with the investigators. During
questioning, James came across to the officers as equal parts defiant and annoyed. After
approximately two hours of questioning, police offered James coffee and a cigarette and allowed
him to use the restroom. After he had rested, investigators returned to questioning him. James
consistently denied any wrongdoing, so the officers reminded him that they had footage of the
crime.
James accused investigators of being incompetent and continued to proclaim his
innocence. The officers countered by playing the tape of the crime and pointing out that he was
wearing blue jeans and a dark coat just like the perpetrator. Investigators also reminded James
that, like the perpetrator in the video, he is a smoker and he was found with just over $80 in his
wallet right after $75 was reported missing. Officers continued to question James over the course
of the next two hours. During this time, the officers again reminded James of the evidence they
had against him at which point James confessed to the crime. He told the police that he was
smoking a cigarette while walking by a woman in the parking garage and saw her purse. He told
of how he hit her in the back of the head and then fled the scene on foot after grabbing the purse.
After verbally confessing, investigators had James write out his confession by hand and sign it.
50
After bringing James to the police station, officers returned to the parking garage to
interview local shop owners about whether they witnessed anyone entering the parking garage
around the time of the crime. Diane Forrester, a hair stylist at a salon half a block from the
parking garage, informed police that she remembered seeing a young man enter the parking
garage while smoking a cigarette. When asked what time this occurred, Diane informed the
officers that she was closing up the salon at the time so it would have been just past 8:30pm. She
described the man as being somewhere between his late twenties to early thirties and light
skinned. Diane told police that the man had short, dark hair and was wearing blue jeans with a
black coat. She also thought that he may have had facial hair.
Officers showed Diane Forrester a lineup that included James. Diane took her time and
carefully examined each of the individuals in the lineup before she eventually identified James as
the man that she had seen outside of the parking garage. After Diane had identified James,
officers asked her how certain she was that the man she identified from the lineup was the man
she had seen at the parking garage. Diane informed the investigating officers that she thought he
was the man she saw, but that she was not certain.
51
After a few nights spent in jail, James requested to speak to investigators. James claimed
that he was innocent and that he had an alibi. He told police that he was at a restaurant at the time
of the crime and that he could prove it as he used his MasterCard to pay his bill. Investigators
checked credit card records and found that his card was used to make a purchase at a local
steakhouse shortly before the crime took place. James’ lawyer proclaimed that this provided
clear evidence of his client’s innocence and moved to have James released immediately. Police
were not convinced, however, because James could have easily given his card to someone else to
use. Because there were no security cameras at the restaurant, this possibility could not be ruled
out.
Investigators obtained access to restaurant records for the night in question and contacted
everyone who made a purchase by credit card that evening. Of the twelve individuals contacted,
one claimed to have seen James at the restaurant. Susan Brayshaw was at the restaurant with her
father for his birthday. She claimed that a man matching James’ description was seated at the bar
across from her booth while she was having dinner. Upon request, Susan came to the police
station where investigators assembled a lineup. Susan identified James as the man from the
restaurant. Officers asked Susan how certain she was that the man she identified from the lineup
was the man she saw at the restaurant. She responded that she thought it was him. However, she
also explained that she had several drinks on the night in question and that her memory for the
night was a little hazy.
52
APPENDIX D. GUILT JUDGMENTS
1.) Based on the information presented in the criminal report, if you had to choose would you say
that Kyle James is more likely to be guilty or innocent?
❏ – Guilty ❏ – Innocent
2.) How confident are you in your decision?
1 2 3 4 5 6 7 8 9 10
Not At All Very
Confident Confident
3.) How likely do you think it is that James is guilty?
1 2 3 4 5 6 7 8 9 10
Very Very
Unlikely Likely
53
APPENDIX E. PERCEPTIONS OF IMPARTIALITY
1.) To what extent was your Assessment based on the evidence provided within the crime report?
1 2 3 4 5 6 7 8 9 10
Not At All Completely
Evidence-Based Evidence-Based
2.) How impartial was your Assessment of the case?
1 2 3 4 5 6 7 8 9 10
Not At All Completely
Fair and Impartial Fair and Impartial
54
APPENDIX F. MANIPULATION CHECK
1.) When did you learn that the suspect in the case confessed to committing the crime?
a.) NEVER – the suspect did not confess to the crime
b.) The FIRST time I read the crime report
c.) The SECOND time I read the crime report
2.) After you read the crime report for the first time, how strong was your belief that the suspect
was guilty or innocent?
1 2 3 4 5 6 7 8 9 10
Very
Weak
Belief
Very
Strong
Belief
3.) After you read the crime report for the first time, how strong would new evidence had to have
been for you to change your verdict from guilty to innocent or innocent to guilt?
1 2 3 4 5 6 7 8 9 10
Not Very
Strong
Very
Strong
4.) Thinking about your final verdict in this case, how difficult would it be for someone to
convince you to change your verdict from guilty to innocent or from innocent to guilty?
1 2 3 4 5 6 7 8 9 10
Not Very
Difficult
Very
Difficult
5.) Thinking about your final verdict in this case, how strong would new evidence have to be for
you to change your verdict from guilty to innocent or innocent to guilt?
1 2 3 4 5 6 7 8 9 10
Not Very
Strong
Very
Strong
55
APPENDIX G. ATTENTION CHECK
1.) What was the suspect’s name?
a.) Steve Park
b.) Mark Lindsay
c.) Kyle James
d.) Ryan Johnson
2.) Did the suspect confess to the crime?
a.) Yes
b.) No
3.) What was the suspect’s alibi?
a.) He was at the dentist
b.) He was at a restaurant
c.) He was at his nephew’s graduation
d.) He was at a baseball game
4.) Did the suspect’s clothes match the perpetrator’s clothing from the video?
a.) Yes
b.) No
5.) Was the suspect found with cigarettes?
a.) Yes
b.) No
6.) Did the suspect have a similar amount of cash as was stolen?
a.) Yes
b.) No
7.) Was the suspect found with house keys stolen from the purse?
a.) Yes
b.) No
8.) Did an eyewitness identify the suspect as being near the scene of the crime?
a.) Yes
b.) No
56
APPENDIX H. SUSPICION CHECK
1.) Sometimes experiments study questions that are not obvious. Do you believe that is the case
in this experiment? No: Yes: If yes, please indicate what research questions you
believe might be under investigation in this experiment.
2.) Please indicate what you knew about this experiment before participating.
3.) Please rate as honestly as possible how believable you found the experimenter when he or she
informed you that some of the materials had been left out. This question will remain anonymous
and the experimenter will never learn of your rating
1 2 3 4 5 6
Completely
Unbelievable
Moderately
Unbelievable
Slightly
Unbelievable
Slightly
Believable
Moderately
Believable
Completely
Believable
57
APPENDIX I. SCRAMBLED ANAGRAMS
A scrambled anagram is a word or phrase made that has had its letters reordered. For example,
the letters ‘plepa’ can be rearranged to create the word ‘apple’.
Please attempt to solve the following scrambled anagrams:
1.) House suhoe 23.) Down dnwo
2.) Screwdriver drrviewecsr 24.) Archive eiahcvr
3.) College ceeogll 25.) Left lfte
4.) Laptop lpaotp 26.) Answer earnws
5.) Dish dhsi 27.) Contact cottanc
6.) Work rkow 28.) Straight ttiahgrs
7.) Laundry ladrynu 29.) Suit tius
8.) Truck tckur 30.) Present teenspr
9.) Coffee efefoc 31.) Thrill llhrti
10.) Vacuum uumavc 32.) Thursday daysurht
11.) Driveway yweavird 33.) Gossip poigss
12.) Baseball lblbaaes 34.) Sneeze eeenzs
13.) Purple plperu 35.) Heaven neeavh
14.) Canada caaand 36.) Ruler rlure
15.) Clothes coheslt 37.) Push phus
16.) Stairs sritas 38.) Electric eccirtel
17.) Rocket koctre 39.) Cake eack
18.) Mail alim 40.) Oxygen nyxgeo
19.) Bump bmpu 41.) Boss bsso
20.) Dance dcnea 42.) Seven svnee
21.) Glass gssla 43.) Bacon bcnoa
22.) Plane pealn 44.) Spoon soonp
58
APPENDIX J. INSTITUTIONAL REVIEW BOARD APPROVAL FORM

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