Vigilance for Differences: Heightened Impact of Differences on Surprise

Abstract

Two experiments tested the hypothesis that humans are vigilant for differences between stimuli in the environment by comparing the amount of surprise elicited by unexpected differences versus unexpected similarities. In Experiment 1, participants performed a weight judgment task where their implicit expectancies about the relative sizes of two wooden blocks were violated. For some participants, the unexpected event was that the two blocks differed in size when participants expected them to be similar in size; for other participants, the unexpected event was that the two blocks were the same size when participants expected them to differ in size. Unexpected differences in size produced greater spontaneous expressions of surprise and mirth than did unexpected similarities in size. Experiment 2 replicated the surprise finding when participants’ expectancies about weight were violated, rather than size. These findings are consistent with the idea that people are more attuned to differences between stimuli in the environment than to similarities.