In a series of experiments, David Levari et al. reveal how people are deceived by their own perceptions, where threatening or harmful stimuli are perceived as remaining abundant even when they are, in fact, decreasing in prevalence. The results underscore the power of perception bias, which could affect a wide range of important decisions, such as those made by police officers or research ethics board members, for example. Psychologists have long known that people make judgements in a highly relative context. For example, when unprovoked attacks and invasions decline in prevalence, behaviors previously deemed less aggressive may then be perceived as more hostile. To better explore this phenomenon, Levari et al. showed volunteers a series of 1,000 dots that varied on a continuum from very purple to very blue, and asked them to decide whether each dot was blue or not. After many trials, the prevalence of blue dots was decreased for one group but not the other. However, even if the number of blue dots decreased, participants perceived the same number of blue dots to exist. Importantly, several additional experiments revealed that this misperception remained in place even if participants were told that the blue dots would definitely decrease, when the decrease happened very suddenly, and when participants were given monetary incentives to report the decrease. But is this a subtle bias, or one more widely applicable to complex scenarios? The authors conducted similar experiments with faces that were rated as "threatening" or "neutral." When threatening faces became rare, participants reported neutral faces as more threatening. Lastly, the authors found a similar shift in the prevalence and rating of "unethical" research proposals.
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Journal
Science