Contextual Effects in Face Lightness Perception Are Not Expertise-Dependent

Racial salience modulated the face race lightness illusion: A comparative study of Caucasians and Asians

Previous research has demonstrated the existence of the face race lightness (FRL) illusion. It indicates that Black faces tend to appear darker than White faces, even when their luminance values are objectively adjusted to be the same. However, the debate over the exclusive influence of face-race categories on the FRL illusion continues, with the impact of racial groups on the illusion remaining relatively unexplored. To address these gaps, we conducted studies to investigate whether the FRL illusion varies in terms of racial salience and racial groups. We manipulated the racial salience by altering the orientation of the faces. A total of 64 Caucasians (Study 1) and 63 Asians (Study 2) were recruited. Participants were shown pairs of faces in rapid succession and were asked to report which face appeared lighter or darker. In each trial, the two faces belonged to the same race category: Black, Black-White ambiguous, or White. The luminance of the first face remained consistent across trials while the luminance of the second face varied and was adjusted across eight levels (- 20, - 12, - 8, - 4, + 4, + 8, + 12, + 20). Our findings reveal that the FRL illusion is largely dependent on the salience of face-race information. When faces were presented upright, the FRL illusion was prominent; however, it disappeared when faces were inverted. Remarkably, the FRL illusion was observed not only in Caucasians but also in Asians. Therefore, our results suggest that the FRL illusion primarily stems from race salience rather than participants' racial groups.

Modulations of depth responses in the human brain by object context: Does biological relevance matter?

Depth sensitivity has been shown to be modulated by object context (plausibility). It is possible that it is behavioural relevance rather than object plausibility per se which drives this effect. Here, we manipulated the biological relevance of objects (face or a non-face) and tested whether object relevance affects behavioural sensitivity and neural responses to depth-position. In a first experiment, we presented human observers with disparity-defined faces and non-faces, and observers were asked to judge the depth position of the target under signal-noise and clear (fine) task conditions. In the second experiment, we concurrently measured behavioural and fMRI responses to depth. We found that behavioural performance varied across stimulus conditions such that they were significantly worse for the upright face than the inverted face and the random shape in the SNR task, but worse for the random shape than the upright face in the feature task. Pattern analysis of fMRI responses revealed that activity of FFA was distinctly different during depth judgments of the upright face versus the other two stimuli, with its responses (and to a stronger extent, those of V3) appearing functionally-relevant to behavioural performance. We speculate that FFA is not only involved in object analysis, but exerts considerable influence on stereoscopic mechanisms as early as in V3 based on a broader appreciation of the stimulus' behavioural relevance.Significance StatementWe asked how disparity sensitivity is modulated by object (biological) relevance using behavioural and neuroimaging paradigms. We show that behavioural sensitivity to depth-position changes in biological (face) vs non-biological (random surface) contexts, and that these changes are task-dependent. Imaging results highlight a potentially key role of the fusiform region for governing the modulation of stereo encoding by object relevance. These findings highlight powerful interactions between object recognition mechanisms and stereoencoding, such that the utility of disparity information may be up/down weighed depending on the biological relevance of the object.