The Myth of Rationality: Cognitive Biases and Heuristics in Judicial Decision-Making

Authors Willem H Gravett

ISSN: 1996-2177
Affiliations: Senior Lecturer, Department of Procedural Law, University of Pretoria
Source: South African Law Journal, Volume 134 Issue 1, 2017, p. 53 – 79


From Plato until the early 1970s, humankind operated under two broad assumptions: (1) people are generally rational; and (2) when people depart from rationality, emotions are likely to blame. However, in 1974 experimental psychologists started documenting systematic errors in the thinking of ‘normal’ people that they traced to the basic design of the machinery of cognition, rather than to the corruption of thought by emotion. They found that human beings rely on cognitive shortcuts to generate judgements without having to consider all the relevant information, relying instead on a limited set of cues. A range of empirical studies in the United States and Europe show that judicial decision-makers are susceptible to some of these cognitive biases. Even if judges have no conscious prejudice against either litigant, understand the law, and know the facts, they might still make systematically erroneous decisions because of how they — like all human beings — think. The purpose of this article is to start to acquaint the South African judiciary with these traps of the mind. There seems to be no empirical research on the effects of these cognitive biases on judicial decision-making in South Africa. This is a perilous deficiency in scholarship that must be addressed.