In 1995, O. J. Simpson was tried for the murder of his ex-wife, Nicole Brown Simpson, and her friend, Ron Goldman, both of whom had been found with multiple knife wounds. To the surprise of many, the jury found Simpson not guilty of the crime, and many explanations have been given for the verdict, ranging from emotional bias on the part of the jury to incompetence on the part of the prosecution. Of course, there is also the possibility that, given the evidence presented to them, the jury rationally made the decision that Simpson was not guilty beyond a reasonable doubt. This paper evaluates four competing psychological explanations for why the jury reached the verdict they did:1. Explanatory coherence. The jury found O. J. Simpson not guilty because they did not find it plausible that he had committed the crime, where plausibility is determined by explanatory coherence.2. Probability theory. The jury found O. J. Simpson not guilty because they thought that it was not sufficiently probable that he had committed the crime, where probability is calculated by means of Bayes's theorem.3. Wishful thinking. The jury found O. J. Simpson not guilty because they were emotionally biased toward him and wanted to find him not guilty.
Emotional coherence.The jury found O. J. Simpson not guilty because of an interaction between emotional bias and explanatory coherence.I will describe computational models that provide detailed simulations of juror reasoning for explanatory and emotional coherence, and argue that the latter account is the most plausible. Application to the Simpson case requires expansion of my previous theory of 2 emotional coherence to introduce emotional biasing of judgments of explanatory coherence.Social psychologists distinguish between "hot" and "cold" cognition, which differ in that the former involves motivations and emotions (Abelson, 1963;Kunda, 1999).The first two explanations above involve cold cognition, the third based on wishful thinking involves only hot cognition, but my preferred emotional-coherence explanation shows how hot and cold cognition can be tightly integrated.
Explanatory CoherenceAt first glance, the evidence that O. J. Simpson was the murderer of his ex-wife was overwhelming. Shortly after the time that the murder took place, he caught a plane to Chicago carrying a bag that disappeared, perhaps because it contained the murder weapon and bloody clothes. Police who came to Simpson's house found drops of blood in his car that matched his own blood and that of Ron Goldman. In Simpson's back yard, police found a bloody glove that was of a pair with one found at the scene of the crime, and they found a bloody sock in his bedroom. Simpson had a cut on his hand that might have been caused by a struggle with the victims who tried to defend themselves.Simpson's blood was found on a gate near the crime scene. Moreover, there was a plausible motive for the murder, in that Simpson had been physically abusive to his wife while they were married and was reported to have been jealous of other men w...