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Kieran J Pang, Colin W G Clifford; Contextual Modulation in High-Level Vision: Evidence for a Spatial Viewpoint Illusion in the Perception of Faces. Journal of Vision 2019;19(10):229b. https://doi.org/10.1167/19.10.229b.
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© ARVO (1962-2015); The Authors (2016-present)
Contextual modulation, the shift in perceptual properties of a target as a function of its surroundings, has been previously demonstrated to be analogous across temporal and spatial dimensions. This relationship has been widely investigated in low-level vision, holding true for properties such as orientation, colour, and motion. However, in high-level vision, while contextual modulation by time has been evidenced, such as through facial viewpoint adaptation, the effects of spatial context are generally unexplored. The present study series utilized an unbiased two-alternative forced choice paradigm to measure the presence and magnitude of a novel viewpoint illusion, an effect taken to be spatially analogous to viewpoint adaptation. Per trial, participants were tasked to select one of two face sets, each consisting of one centred target identity surrounded by six distinct faces, depending on which target was oriented more directly forward. The flankers of one set faced to the left of the observer, while the respective faces of the other set mirrored this, oriented to the right. The orientations of the two target faces deviated equally in either direction away from a base orientation, as selected by a Bayesian staircase procedure. A small repulsive effect of approximately 0.5° was observed and subsequently replicated. That is, judgements of a centre face’s viewpoint were shifted from its true orientation, in a direction opposite to the orientation of faces present in the surround. This effect was eliminated following inversion of the spatial surround, indicating that it was not driven by aggregated low-level effects. The results of this study provide evidence that contextual modulation in the spatial domain is present beyond low-level vision, and additionally open the field to investigating the role of spatial interactions in the processing of other high-level facial properties with established adaptation effects, such as emotion, identity, and gaze.
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