Thursday, October 15, 2009

The psychology of expert testimony: Select research

Below are three empirical studies addressing the evaluation of expert testimony and variables impacting the acceptance of expert testimony.  They have been sitting in my "to read" in box since I started this blog.  I had intended to digest all three and post some general comments.  I now realize I'll likely never get to these in the near future, so rather than having them sit and be of no value, I instead have decided to post the references, abstracts, and provide links to the articles to those who want to read more in depth.  These are only a handful of studies.  It is my guess that there is a large body of empirical research (and books and/or book chapters) on expert testimony.  This post is not intended to be comprehensive.

The decision to post these three empirical studies was spurred by my last nights reading of a very interesting article in the current issue of the American Psychologist (2009, Vol 64, No. 6).  The article (Conditions for intuitive expertise: A failure to disagree) is by Daniel Kahneman and Gary Klein.  Below is the abstract following by some key conclusions.
This article reports on an effort to explore the differences between two approaches to intuition and expertise that are often viewed as conflicting: heuristics and biases (HB) and naturalistic decision making (NDM). Starting from the obvious fact that professional intuition is sometimes marvelous and sometimes flawed, the authors attempt to map the boundary conditions that separate true intuitive skill from overconfident and biased impressions. They conclude that evaluating the likely quality of an intuitive judgment requires an assessment of the predictability of the environment in which the judgment is made and of the individual’s opportunity to learn the regularities of that environment. Subjective experience is not a reliable indicator of judgment accuracy.

I zeroed in on the articles material that dealt with issues surrounding the development of expertise and conditions impacting expert judgments.  Although the research is not specific to expert testimony in court proceedings (as are the other three articles listed in this post), I found some specific conclusions worthy of mention and reflection, particularly after reading and thinking about a number of Atkins rulings discussed at this blog (all that included dueling psychological experts).  Below are a few conclusions and statements worthy of consideration.  Unless otherwise noted via underlining or bracket comments, these are all direct quotes from the article.
  • Kahneman coined the term illusion of validity for the unjustified sense of confidence that often comes with clinical judgment.
  • The intuitive judgments of some professionals are impressively skilled, while the judgments of other
    professionals are remarkably flawed.
  • Skilled judges are often unaware of the cues that guide them, and individuals whose intuitions are not skilled are even less likely to know where their judgments come from.
  • True experts, it is said, know when they don’t know. [emphasis added by blogmaster...I think this is a critical finding] However, nonexperts (whether or not they think they are) certainly do not know when they don’t know. Subjective confidence is therefore an unreliable indication of the validity of intuitive judgments and decisions.
  • The situation that we have labeled fractionation of skill is another source of overconfidence. Professionals who have expertise in some tasks are sometimes called upon to make judgments in areas in which they have no real skill.... It is difficult both for the professionals and for those who observe them to determine the boundaries of their true expertise. [emphasis added by blogmaster - this is so true and dangerous.  People often assume, since I develop intelligence tests and conduct research on intelligence theories, that I must know everything about these two topics.  Often when asked questions that are at my boundaries of expertise, it is tempting to provide an answer based on partial knowledge....but, consistent with the prior point emphasized above, the more professional response is to recognize one's limits of expertise and simply say "I don't know."  I wonder how often psychological experts in Atkins cases are faced with this fractionalization of skill expertise conflict?]

Kruass, D. A. & Sales, B. D. (2001). The effects of clinical and scientific expert testimony on juror decision making in capital sentencing. Psychology, Public Policy, and Law, 7 (2), 267-310. (click to view)
The Supreme Court and many state courts have assumed that jurors are capable of differentiating less accurate clinical opinion expert testimony from expert testimony based on more sound scientific footing and of appropriately weighing these two types of testimony in their decisions. Persuasion and jury decision-making research, however, both suggest that this assumption is dubious. The authors investigated whether mock jurors are more influenced by clinical opinion expert testimony or actuarial expert testimony. Results suggested that jurors are more influenced by clinical opinion expert testimony than by actuarial expert testimony and that this preference for clinical opinion expert testimony remains even after the presentation of adversary procedures. Limited empirical evidence was found for the notion that various types of adversary procedures will have a differential impact on the influence of expert testimony on juror decisions.

Levett, L. M. & Kovera, M. B. (2009).  Psychological mediators of the effects of opposing expert testimony on juror decisions.  Psychology, Public Policy, and Law, 15 (2), 124–148. (click to view)
This study examined the effectiveness of the opposing expert safeguard against unreliable expert testimony and whether beliefs about experts as hired guns and general acceptance mediate the effect of opposing expert testimony on juror decisions. We found strong evidence that the presence, but not the content, of opposing expert testimony affected jurors’ trial judgments and that these effects were mediated by mock jurors’ beliefs about general acceptance. The presence of an opposing expert affected jurors’ ratings of the general acceptance of research investigating sexual harassment in the workplace. Jurors’ beliefs about general acceptance then affected jurors’ ratings of plaintiff expert competence and research, which affected juror ratings of the probability that the plaintiff experienced a hostile work environment.

Schweitzer, N. J. & Saks, M. J. (2009).  The gatekeep effect: The Impact of Judges’ Admissibility Decisions on the Persuasiveness of Expert Testimony. Psychology, Public Policy, and Law, 15 (1), 1-18) (click to view)
In a pair of mock-trial studies of a possible “gatekeeper” effect, our participants were presented with a summary of a trial that included a piece of expert scientific evidence. The judge’s decision was manipulated to admit the scientific evidence, as well as the quality of the evidence and the credibility of the expert. Participants were found to be less critical of and more persuaded by expert evidence when it was presented within a trial, compared with the same evidence presented outside of a courtroom context. These findings suggest that, when judges allow expert testimony to reach the jury although the evidence is of low quality, they imbue it with undeserved credibility. Furthermore, no changes in participants’ perceptions of the evidence were found if the mock jurors were explicitly informed that the judge had evaluated the evidence, suggesting that the participants assumed that judges normally review evidence before allowing it to reach the jury. In addition, implications for basic research are discussed, as the moderating effects of a gatekeeper have not previously been considered by established models of persuasion.

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