Disrupting perceptual grouping of face parts impairs holistic face processing

Abstract

Face perception is widely believed to involve integration of facial features into a holistic perceptual unit, but the mechanisms underlying this integration are relatively unknown. We examined whether perceptual grouping cues influence a classic marker of holistic face perception, the “composite-face effect.” Participants made same–different judgments about a cued part of sequentially presented chimeric faces, and holistic processing was indexed as the degree to which the task-irrelevant face halves impacted performance. Grouping was encouraged or discouraged by adjusting the backgrounds behind the face halves: Although the face halves were always aligned, their respective backgrounds could be misaligned and of different colors. Holistic processing of face, but not of nonface, stimuli was significantly reduced when the backgrounds were misaligned and of different colors, cues that discouraged grouping of the face halves into a cohesive unit (Exp. 1). This effect was sensitive to stimulus orientation at short (200 ms) but not at long (2,500 ms) encoding durations, consistent with the previously documented temporal properties of the holistic processing of upright and inverted faces (Exps. 2 and 3). These results suggest that grouping mechanisms, typically involved in the perception of objecthood more generally, might contribute in important ways to the holistic perception of faces.

Holistic processing of static and moving faces.

“…Consistent with this dual-route hypothesis, holistic processing of faces can be reduced or eliminated by disrupting object-based grouping of facial parts, despite humans having life-long experience in individuating faces (Curby et al, 2013;Zhao et al, 2016b).…”

“…Alternatively, the contribution of rigid motion to holistic processing may be overshadowed by more salient cues supporting holistic face processing. Rigid motion provides additional Gestalt cues for grouping facial parts together (Piepers & Robbins, 2012;Wagemans et al, 2012), which should facilitate holistic processing according to the dual-route hypothesis (Curby et al, 2016;Curby et al, 2013;Zhao et al, 2016aZhao et al, , 2016b. However, such facilitation may be less evident when holistic processing can be activated by more influential factors (e.g., those provided by normal upright faces and expertise with them), which leaves little room for facial motion to further enhance holistic processing.…”

“…Besides the two influential theories mentioned above, recent studies suggest that both object-based (i.e., bottom-up route) and experience-driven (i.e., top-down route) perceptual grouping contribute to holistic processing (Zhao, Bülthoff, & Bülthoff, 2016a, 2016b; see also Curby, Entenman, & Fleming, 2016;Curby, Goldstein, & Blacker, 2013;Zhou, Cheng, Zhang, & Wong, 2012). Consistent with this dual-route hypothesis, holistic processing of faces can be reduced or eliminated by disrupting object-based grouping of facial parts, despite humans having life-long experience in individuating faces (Curby et al, 2013;Zhao et al, 2016b).…”

“…Whether holistic processing is supported by a perceptual gating process based on innate face template (Tsao & Livingstone, 2008), by a domain-specific process that applies to faces or objects that are sufficiently facelike , by learned attention from expertise training (Chua et al, 2015;Richler, Wong, et al, 2011), or by object-based perceptual grouping (Curby et al, 2013;Zhao et al, 2016a), it should not be eliminated by rigid facial motion. This is because rigid facial motion does not eliminate any of these processes known to support holistic processing.…”

“…With regard to the expertise hypothesis, if the automatic attention to multiple diagnostic facial parts drives holistic face processing (Richler, Wong, et al, 2011;Chua et al, 2015), both a top-down route (i.e., learned attention) and a bottom-up route (i.e., motion-based perceptual grouping) should be able to activate such holistic attention (Curby et al, 2013(Curby et al, , 2016Wong et al, 2009;Zhao et al, 2016a). Robust holistic processing of moving faces also suggests that expertise helps the visual system to develop integrative models for the spatiotemporal dynamics of natural facial movements, so that correlated movements of facial features (e.g., how eyes and mouth move during yawn or smiling) will be processed in a perceptually integrative way (Cook et al, 2015;Reinl & Bartels, 2014).…”