Visual adaptation and face perception

Abstract

The appearance of faces can be strongly affected by the characteristics of faces viewed previously. These perceptual after-effects reflect processes of sensory adaptation that are found throughout the visual system, but which have been considered only relatively recently in the context of higher level perceptual judgements. In this review, we explore the consequences of adaptation for human face perception, and the implications of adaptation for understanding the neural-coding schemes underlying the visual representation of faces. The properties of face after-effects suggest that they, in part, reflect response changes at high and possibly face-specific levels of visual processing. Yet, the form of the after-effects and the norm-based codes that they point to show many parallels with the adaptations and functional organization that are thought to underlie the encoding of perceptual attributes like colour. The nature and basis for human colour vision have been studied extensively, and we draw on ideas and principles that have been developed to account for norms and normalization in colour vision to consider potential similarities and differences in the representation and adaptation of faces.

Perceptual face processing in developmental prosopagnosia is not sensitive to the canonical location of face parts

“…The hypothesis that a canonical upright face template plays a critical role during early stages of perceptual face processing is consistent with evidence from visual adaptation studies which have demonstrated that the average face in a set of face images is crucial for inducing identity-specific visual aftereffects (Leopold, O'Toole, Vetter, & Blanz, 2001;Webster & Macleod, 2011;Rhodes & Leopold, 2011). An fMRI study (Loffler, Yourganov, Wilkinson, & Wilson, 2005) has suggested that the neural locus of this prototype-based face encoding may be the FFA, a brain region known to be causally involved in high-level aspects of normal face perception (Parvizi et al, 2012;Barton, Press, Keenan, & O'Connor, 2002;2008;Kanwisher & Barton, 2011).…”

Neuronal correlates of a visual “sense of number” in primate parietal and prefrontal cortices

“…This finding was recently supported by a computational network model in which sensitivity to numerosity spontaneously developed (11). However, because adaptation is not restricted to primary visual attributes, but also observed for high-level visual categories such as faces (27), the category visual numerosity may alternatively be appreciated as a special perceptual category represented spontaneously in a dedicated parietofrontal network. Other complex visual categories are also represented in the primate visual system up to the frontal lobe in a relatively specialized fashion: faces, places, and body parts appear to have dedicated neural substrates for their representation (28,29,30,31).…”

Overweight but unseen: a review of the underestimation of weight status and a visual normalization theory

“…In other words, the size of a stimulus (e.g. body size) a person is used to seeing in his or her environment is likely to directly inform his or her visual perception of stimulus normality, a process that is frequently referred to as ‘visual adaptation’ 74, 75 or the ‘visual diet’ 68, 76. Because visual body‐weight norms will be similarly shaped by experience 77, 78, it is proposed that increased exposure to obesity will recalibrate the range of body sizes that are perceived by most people as being ‘normal’, as well as increasing the size at which a body is categorized as overweight.…”