Do we see what we feel? A comparative study of spider size estimation among experts and people who are highly fearful of spiders.

The existence of fear-driven perceptual biases is well-established in the research literature and explained by survival mechanisms, whereas findings on perceptual biases among experts remain inconsistent. This study is the first to compare the impact of emotion and expertise on perception by examining spider size estimation among spider-fearful individuals (N = 58), spider experts (N = 59) and a control group (N = 52). Participants estimated the size of spiders, butterflies and wasps depicted in pictures. In line with prior findings, highly fearful individuals overestimated the size of spiders but not the size of butterflies, while control group members rated the two types of animals similarly. Spider experts demonstrated relatively accurate size estimation across all stimuli. These results highlight the dominant role of emotion over expertise in perceptual biases, with spider-fearful individuals exaggerating spider size and experts maintaining accuracy. This study bridges the gap between emotion-driven and expertise-driven perceptual biases, offering insights into the differential effects of fear and specialised knowledge on visual perception.