It’s all relative: Effect of contrast cases on jury members’ decision making

It’s all relative: Effect of contrast cases on jury members’ decision making

Prosecutors, individuals involved in criminal justice, and general public serving as jury members should be aware of the contrast effects when making judgements in a legal context. This is the bottom line of a recently published article in Psychology, Public Policy, and Law. Below is a summary of the research and findings as well as a translation of this research into practice.

Featured Article | Psychology, Public Policy, and Law | 2019, Vol. 25, No. 1, 30–37

A social judgement? Extralegal contrast effects in hypothetical legal decision making


Max E. Butterfield, Point Loma Nazarene University
Alexandra, N. Bitter, The University of Wyoming


Social judgments in ambiguous situations often rely on heuristics and biases, and legal decision makers are often faced with evidence that does not clearly favor one decision over another. Across two studies, we tested whether one extralegal factor, contrast cases, influenced decision making when judicial factors were held constant. In Study 1, participants (n = 100) evaluated whether an imagined prosecutor had sufficient evidence to send the same three target cases to trial. Before deciding these cases, though, the participants first evaluated cases with either relatively stronger or weaker evidence than the targets. Those in the weak-case comparison group were significantly more likely to send target cases to trial, and they believed the prosecutor had a stronger case. In Study 2, all participants (n = 100) evaluated hypothetical parole applications, but the method was otherwise the same as that used in Study 1. The same contrast-oriented pattern emerged. Participants who first viewed weaker parole applications rated the identical targets as significantly more rehabilitated. Taken together, the results of these two studies suggest that contrast effects may be one extralegal factor involved in shaping individual-level social judgments made in legal contexts such as grand juries and parole boards.


contrast effects, decision making, grand juries, parole boards, heuristics

Summary of the Research

“Objectivity is a cornerstone of the American justice system, and legal decisions are supposed to be based on the strength of available evidence. Research findings do provide at least partial support for the ideal: In many instances, strong cases win and weak cases do not. However, what happens when the strength of evidence does not completely favor one side or the other? A growing body of research has demonstrated that a variety of extralegal factors affect legal decision making. Generally, ambiguous conditions in any domain increase the likelihood that heuristics and biases will influence social judgments, but we were especially curious about how they might affect legal decision making, especially when such processing might be inadvertently or systematically activated in all decision makers involved in a particular case. Among some of the most noteworthy of these are pretrial publicity; the CSI effect; and the race, sex, and gender of the defendant.” (p. 30)

“Our express purpose in the present investigation was to focus on the role of ambiguity in basic social judgments made by individuals. Specifically, we wondered whether contrast cases presented before target cases might be an influence over and above the other extralegal factors that have been more thoroughly documented elsewhere. We hypothesized that making additional cases cognitively accessible to individual evaluators would subtly provide reference points for judging case strength, thereby influencing what otherwise appear to be objective ratings of target cases.” (p. 30)

“Social judgments based on prejudices and stereotypes […] typically rely on systematic processes: Rather than carefully deliberating decisions based on known facts about the individuals being evaluated, mental shortcuts bias and shape inferences instead. Anchoring Effect is but one example of Social Judgment Theory’s emphasis on the importance of reference points in decision making. For many years, in fact, researchers worked to resolve an apparent paradox in which some reference points were observed to create assimilation effects, whereas others lead to contrast effects. Assimilation occurs when target stimuli are evaluated as more similar to an anchor/reference, whereas contrast creates the opposite effect, and evidence has mounted to demonstrating that assimilation and contrast are driven by the features of the references and stimuli that are cognitively accessible at the point of evaluation. […] studies over the years have demonstrated the role of contrast extends beyond physiological and person perception judgments and appears to apply to cognitions across the spectrum of judgment and decision making. However, few studies have specifically explored in depth the ways in which contrast might affect decision making in legal contexts, and although the application is intuitive, empirical investigation has been limited” (p. 31)

“Because the U.S. justice system relies heavily on untrained volunteers for jury service, we believe it is particularly important to determine how social judgment affects legal decision making. Unfortunately, evidence does support the notion of consistent bias in some circumstances, especially in cases where the strength of evidence does not clearly favor one side or another. It is in these cases that jurors may find themselves unable to make decisions based solely facts of the cases they are considering, and they instead rely on intuitions, biases, or mental shortcuts to tip the scales in one direction or another.” (p. 31)

“We specifically wondered whether weak-contrast comparison cases would make target cases appear strong, whereas strong-contrast target cases would make those same target cases appear weak, simply because of the directionally oriented high evaluative contrast created by the cognitive accessibility of the recent comparators. Study 1 was designed to test this hypothesis using a hypothetical grand jury experience. A grand jury setting was chosen for the initial study because, unlike petit juries, they do not reach final case outcome decisions and they can make decisions about multiple cases. Instead, individuals who sit on grand juries decide if the cases they consider have sufficient evidence for a prosecutor to send them to trial, and the jurors are typically exposed to multiple cases in sequence over the course of their time spent serving. Thus, it seemed more ecologically valid to ask participants to consider multiple cases.” (p. 32)

“Similarly, parole boards were chosen as the setting for Study 2 for the same reason: Parole boards in many jurisdictions typically evaluate multiple cases in a sequence, often even multiple in the same sitting. The general hypothesis for both studies was that evaluations of case strength would be higher for participants whose expectations were anchored by weak-contrast comparison cases than for those who were anchored by strong-contrast comparison cases.” (p. 32)

“Across two studies, we demonstrated persistent contrast effects. In Study 1, people who imagined themselves on hypothetical grand juries appeared to anchor their standards for evidentiary evaluations using recent cases they also evaluated. More specifically, target cases were evaluated to have stronger evidence and were more likely to be sent to trial if they were evaluated while embedded with weak cases.” (p. 35)

“Study 2 was a conceptual replication of this effect. There, people who imagined themselves on hypothetical parole boards tended to anchor their evaluations of prisoner rehabilitation using previous cases they had evaluated as well. More specifically, compared to those who viewed strong cases for parole (i.e., better rehabilitation), those who viewed weak cases gave more positive evaluations of the target cases. Taken together, the results of these two studies suggest that contrast effects may be one extralegal factor involved in shaping individual-level social judgments made in legal contexts.” (p. 35)

“Ultimately, the limited capacity of human cognitive architecture has been heavily documented across a wide variety of domains, and the extralegal contrast effects shown here seem to be another example of the wide scope of heuristic processing. Although these thinking errors are commonplace, research and practical evidence in those other domains has shown their effects can be minimized or even avoided altogether under the right circumstances. In order for objectivity to be most effectively achieved across the justice system, then, it may be important to devote further study of contrast effects in a judicial context to more fully understand and limit their influence.” (p. 36)

Translating Research into Practice

“For prosecutors, particularly those involved with grand juries, the results indicate the importance of the order in which they present their cases. In situations where they cannot control the order, steps may need to be taken to minimize the impact of particularly strong or weak contrast cases presented directly before or that may remain salient in jurors’ minds. Prosecutors may also wish to use the effect to their advantage in similar ways, and it will be important for them to be aware of the potential that extralegal contrast could unduly influence juries unfairly. Conversely, individuals involved in criminal defense or parole application should likely do everything in their power to disassociate themselves from cases or people who would elicit contrast in the wrong direction, and similarly seek out instances of positive contrast with which to align themselves.” (p. 36)

“Members of the general public who are called to serve on grand juries should also likely be aware of contrast’s extralegal influence. They have a responsibility to weigh the merits of the cases they evaluate as objectively as possible, and they often do this very well. However, in cases where the evidence is ambiguous, or it is unclear whether the strength of evidence in a case meets standards for trial, it is essential that they be made aware of that contrast effects could be sources of extralegal influence. Similarly, those who serve on parole boards take seriously their responsibility to objectively evaluate whether prisoners are rehabilitated. As a result, it is important for them to be aware of possible contrast effects as well.” (p. 36)

“In general, raising awareness for both grand jury and parole board members would not be complex or costly. Simply providing them with information about the phenomenon may be enough to prevent its effects from taking root. However, awareness alone may not be an effective intervention, and legal professionals involved with grand juries or parole boards may wish to seek additional amelioration methods. For example, it could be useful to provide grand jury and parole board members with a standardized contrast case before each target case they consider, effectively neutralizing prior experiences and allowing for more unbiased evaluations. That being said, the effectiveness of these potential intervention, informational or otherwise, should likely be tested in either a basic or applied setting before they are put into widespread practice.” (p. 36)

Other Interesting Tidbits for Researchers and Clinicians

“Unfortunately, ecologically representative research of this nature is notoriously difficult and costly, and like many past studies we decided to use hypothetical scenarios as a first step to determine whether evidence could first be found for a basic effect. That basic effect, however, should be weighed against the fact that grand jury and parole board decisions typically involve a myriad of group process factors that were not at play in the current study. […] Undoubtedly, though, members of actual grand juries and parole boards can be influenced not just by contrast effects, but also by conversations, social influence attempts, reflection after feedback, situational factors, and a variety of other things. The complexity and nuance added by a complete social environment should not be ignored, and future research on this topic should include more realistic directions, in-person simulations, or actual grand jury or parole board members. Ideally, studies would even include deliberative simulations situated in realistic environments.” (p. 35)

“Because the present research used a very simple design testing only the effects of contrast, it is unclear how much variance in jury or parole decision making can actually be explained by contrast effects relative to other extralegal factors. […] further research may wish to explore the relationship between contrast effects and other extralegal factors that have been the subject of previous research inquiries.” (p. 36)

“Finally, it is still unclear how powerful contrast effects are in relation to judicial factors like strength of evidence, and further study is necessary to determine the factors increase the likelihood of reliance on heuristic processing in legal contexts.” (p. 36)

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Authored by

Kseniya Katsman is a Master’s student in Forensic Psychology program at John Jay College of Criminal Justice. Her interests include forensic application of dialectical behavior therapy, cultural competence in forensic assessment, and risk assessment, specifically suicide risk. She plans to continue her education and pursue a doctoral degree in clinical psychology.

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