Adaptation aftereffects in the perception of gender from biological motion

Abstract

Human visual perception is highly adaptive. While this has been known and studied for a long time in domains such as color vision, motion perception, or the processing of spatial frequency, a number of more recent studies have shown that adaptation and adaptation aftereffects also occur in high-level visual domains like shape perception and face recognition. Here, we present data that demonstrate a pronounced aftereffect in response to adaptation to the perceived gender of biological motion point-light walkers. A walker that is perceived to be ambiguous in gender under neutral adaptation appears to be male after adaptation with an exaggerated female walker and female after adaptation with an exaggerated male walker. We discuss this adaptation aftereffect as a tool to characterize and probe the mechanisms underlying biological motion perception.

Gender bending: auditory cues affect visual judgements of gender in biological motion displays

“…Inter footstrike intervals were consistent (950 ms) and initial impact sounds were synchronised with the visual PLWs so that they always occurred at the point in the walking pattern that corresponded with the walkers' feet hitting the ground data suggest that the walker one standard deviation below the objective mean of the gender continuum (walker ¡1) was subjectively the most gender-ambiguous walker, giving rise to equal numbers of female and male judgements (comparing the observed proportion of male responses = 0.412 to the point of subjective ambiguity 0.5; t 9 = ¡0.83, P > 0.05). In those respects these data replicate Wndings reported elsewhere (Brooks et al 2008;Troje et al 2006).…”

“…3a, Wlled circles) and changed from one to the other, according to a linear integration function, as the visual stimuli incremented along the gender continuum. As reported elsewhere for these particular inducing stimuli, subjective gender ratings of the objective gender continuum show a slight "male" bias (Troje et al 2006). That is, the statistically gender neutral walker (walker 0) was judged by observers signiWcantly more often to be male (comparing the observed proportion of male responses = 0.732 to the point of subjective ambiguity 0.5; t 9 = 2.20, P < 0.05).…”

“…Those 123 results suggest gender perceptions are mediated by gendertuned neurons or networks (Jordan et al 2006). The location of such neurons or networks is unclear but both Jordan et al (2006) and Troje et al (2006) suggest extra-striate cortex as a possible location. Troje, however, does not dismiss the possibility that the adaptation eVects might reXect adaptation of low-level motion processes, and the protocols used by that group do not preclude that explanation.…”

“…To test for that possibility in "Experiment 3" we induced gender aftereVects like those described by Jordan et al (2006) and by Troje et al (2006). Both those groups demonstrated that prolonged viewing of a PLW of one gender can give rise to an aftereVect such that subsequently presented PLWs look more like the opposite gender.…”

“…Using timing and protocols described by Troje et al (2006) each trial consisted of an adaptation phase during which the adapting stimulus was presented initially for 14 s. Then one of Wve test stimuli was presented and observers were required to signal the gender of the test walker. Following presentation of each test stimulus, the adapting stimulus was again presented; this time for a 7-s top-up (van der Zwan and Wenderoth 1994) before a second test was presented and that protocol followed until the adapting stimulus had been used with each of the Wve test stimuli (see below).…”