Dissociations between Covariation Bias and Expectancy Bias for Fear-relevant Stimuli

Abstract

The illusory correlation paradigm of Tomarken, Mineka, and Cook (1989) was used to examine bias in threat appraisal for biological (snake, spider) and technological (gun, knife) fear-relevant stimuli. Subjects showed bias in terms of higher on-line shock expectancy ratings and skin conductance responses, and higher post-experimental judgements of shock covariation, for fear-relevant stimuli. However, there were multiple dissociations between the measures: (1) expectancy bias was observed for both biological and technological stimuli, whereas covariation bias was restricted to biological stimuli; (2) prior fear of the target stimulus had no effect on expectancy bias, but covariation bias was restricted to high fear subjects; and (3) covariation bias was observed at the end of the experiment, by which time expectancy bias had disappeared. These results suggest that covariation bias is not simply a continuation of a pre-experimental expectancy bias.