Abstract
Individuals vary widely in how they categorize faces. We examined whether these differences in perceptual judgments are linked to differences in observers' sensitivity to face categories, by comparing the category boundaries for ethnicity chosen by Caucasian students or by Japanese exchange students newly arrived in the US. A 2AFC staircase was used to determine the boundary within a graded image set formed by morphing between individual Caucasian and Japanese faces. Mean categories for the two subject groups differed (though not for all face pairs), consistent with a reduced sensitivity to the observer's own ethnic category. To test for these sensitivity differences, the settings were repeated after adapting to different levels along the morph, to determine the adapting level that did not bias the subject's pre-adapt setting. These neutral adapting levels were strongly correlated with (but varied more than) the subject's subjective ratings, while adapting to a common image greatly reduced the variance in neutral points across all subjects. These results suggest that how observers subjectively rate faces may in part reflect their underlying sensitivity to faces, which may in turn reflect the individual's long-term exposure and adaptation to different distributions of faces.