Bias, cognitive heuristics, and forensic decision-making

The cumulative weight of 30 years of research originating in Tversky and Kaheman’s seminal 1974 description of the mental shortcuts humans use when confronting cognitive ambiguity complexity, and Kahneman’s recent masterpiece Thinking Fast, and Slow (2011, cf. Gilovich, Griffin, & Kahneman, 2002) has created a mature cognitive science of forensic decision-making. The findings are not reassuring to the forensic psychologist.

Human beings are limited in the amount of information they can process. They use short-cuts to make decisions. This applies to people in the street, law enforcement, jurors, and judges, too. Many of these decisions, made under condition of uncertainty, complexity, and pressure are inaccurate and have high rates of error.

Turns out when humans have to make high stakes, complex decisions they try to make connections to their past experience, to events and knowledge that is already familiar to them, or engage in a positive test strategy. Problem is, humans cannot describe their thought process since it is out of awareness; humans have “little or no introspective access to higher order cognitive processes” (Nisbett & Wilson, 1977).

Bias in forensic decision-making may be witting or unwitting. The most egregious type of bias is “partisan allegiance” (Murrie, et al , 2008, 2009), defined as the tendency to bias information according to the side that retained the expert. Biased decision-making may involve cognitive shortcuts and application of decision thresholds, in which costs of decisions are weighed, including personal and professional costs to the decision-making.

Face it, forensic mental health evaluations are risky. What will happen if I say the defendant should be released and the next day he kills somebody? This is a decision cost which is inescapable. In our own research, we have found that forensic decision-making, especially in the “hard to decide zone” is often random.

Neal and Grisso’s (2014) superb piece on three primary decision short-cuts is required reading for any forensic decision-maker. They describe the problem in elegant detail and offer some proposed solutions.

I will discuss this important study in a future blog.


Gilovich, T., Griffin, D., & Kahneman, D. (2002). Heuristics and biases: The psychology of intuitive judgment. New York: Cambridge University Press.

Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185, 1124-1131.

Kahneman, D. (2011). Thinking fast, and slow. New York: MacMillan.

Neal, M., & Grisso, Y. (2014). The cognitive underpinnings of bias in forensic mental health
evaluations. Psychology, Public Policy & Law, prepublication version; doi: 10.1037/a0035824.

Nisbett, & Wilson, (1977). Telling more than we can know: Verbal reports on mental processes. Psychological Review, 84, 3, 231-259.


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