Scrutinizing whether Mere Group Membership Influences the N170 Response to Faces: Results from Two Preregistered ERP Studies

A socially consequential test of the cognitive penetrability of visual perception is whether merely sharing a group membership with another person influences how you encode their face. Past research has examined this issue by manipulating group membership with techniques from social psychology and then measuring the face-sensitive N170 ERP. However, methodological differences across studies make it difficult to draw conclusions from this literature. In our research, we conducted two large-scale, preregistered ERP studies to address how critical methodological decisions could influence conclusions about top-down effects of group membership on face perception. Specifically, we examined how mere group membership, perceptual markers that signify group membership, number of trials included in the study design, the racial/ethnic identity of face stimuli, and the data analytic approach affect inferences about the N170 response to faces. In Study 1, we find no evidence that mere group membership significantly influences the N170. However, we find that the background color used to signify group membership modulated the magnitude and latency of the N170. Exploratory analyses also show effects of stimulus race/ethnicity. In Study 2, we dissociate background color from face encoding by presenting background color before the faces. In this second study, we find no main effect of group membership, background color, or stimulus race/ethnicity. However, we did see an unhypothesized mere group membership effect on trials toward the end of the study. Our results inform debates about social categorization effects on visual perception and show how bottom-up indicators of group membership can bias face encoding.

Lightness matching and perceptual similarity

Lightness constancy is the ability to perceive surface reflectance correctly despite substantial changes in lighting intensity. A classic view is that lightness constancy is the result of a "discounting" of lighting intensity, and this continues to be a prominent view today. Logvinenko and Maloney (2006) have proposed an alternative approach to understanding lightness constancy, in which observers do not make explicit estimates of reflectance, and lightness constancy is instead based on a perceptual similarity metric that depends on both the reflectance and the illuminance of surfaces viewed under different lighting conditions. Here we compare these two views using a novel, free-adjustment reflectance-matching task. We test whether observers can match reflectance in a task where they are free to adjust both the illuminance and the reflectance of the match stimulus over a wide range. We find that observers can match reflectance under these conditions, which supports the view that observers make explicit estimates of reflectance. We also compare performance in this free adjustment task using physical objects and computer-rendered images as stimuli. We find that lightness constancy is good in both cases, but with some evidence of a glow-related artifact with computer-rendered stimuli.