UC Berkeley

Human perceptual decisions are critically important. They can be socially significant, life-changing or even catastrophic if wrong, such as decisions made by radiologists, Olympic judges, TSA screeners, or vehicle operators. Many of these crucial judgments are made based on the perceptual expertise of individual observers. However, not everyone possesses the same level of expertise, even among professionals. There are two aspects that characterize the individual differences in expertise: variations in sensitivity and variations in bias. Past research has thoroughly investigated differences in sensitivity across many domains. However, the possibility of variations in perceptual bias has been largely ignored.

Here, we filled this gap by investigating the idiosyncratic variations in human visual perceptual biases. In the first study, we identified and characterized the unique perceptual biases in position perception and showed that these biases might originate from variations in visual acuity and they can influence the perceived appearance of objects, suggesting that idiosyncratic perceptual biases could propagate through different levels of visual processing and be associated with each other. To understand whether perceptual biases can have a real-world impact, in the second study, we further tested radiologists with artificial and realistic medical images and found that even expert radiologists were characterized with unique and systematic perceptual biases towards medical images. Given the prevalence of perceptual biases, the third study aimed to discover potential constructive ways to utilize the biases. We showed that when multiple observers make a collective decision, grouping individuals who have uncorrelated and thus independent perceptual biases can improve their combined performance.

Together, these results highlighted the crucial importance of measuring and understanding individual perceptual biases and they have widespread implications for many real-world professions and situations such as driving, radiological or TSA screening and Olympic judges.