Perceptual aftereffects following adaptation to simple stimulus attributes (e.g., motion, color) have been studied for hundreds of years. A striking recent discovery was that adaptation also elicits contrastive aftereffects in visual perception of complex stimuli and faces [1-6]. Here, we show for the first time that adaptation to nonlinguistic information in voices elicits systematic auditory aftereffects. Prior adaptation to male voices causes a voice to be perceived as more female (and vice versa), and these auditory aftereffects were measurable even minutes after adaptation. By contrast, crossmodal adaptation effects were absent, both when male or female first names and when silently articulating male or female faces were used as adaptors. When sinusoidal tones (with frequencies matched to male and female voice fundamental frequencies) were used as adaptors, no aftereffects on voice perception were observed. This excludes explanations for the voice aftereffect in terms of both pitch adaptation and postperceptual adaptation to gender concepts and suggests that contrastive voice-coding mechanisms may routinely influence voice perception. The role of adaptation in calibrating properties of high-level voice representations indicates that adaptation is not confined to vision but is a ubiquitous mechanism in the perception of nonlinguistic social information from both faces and voices.

Body size is a salient marker of physical health, with extremes implicated in various mental and physical health issues. It is therefore important to understand the mechanisms of perception of body size of self and others. We report a novel technique we term the bodyline, based on the numberline technique in numerosity studies. One hundred and three young women judged the size of sequentially presented female body images by positioning a marker on a line, delineated with images of extreme sizes. Participants performed this task easily and well, with average standard deviations less than 6% of the total scale. Critically, judgments of size were biased towards the previously viewed body, demonstrating that serial dependencies occur in the judgment of body size. The magnitude of serial dependence was well predicted by a simple Kalman-filter ideal-observer model, suggesting that serial dependence occurs in an optimal, adaptive way to improve performance in size judgments.

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The perception of facial gender has been found to be adaptively recalibrated: adaptation to male faces causes participants to perceive subsequent faces as more feminine and vice versa [Webster, M. A., Kaping, D., Mizokami, Y., & Duhamel, P. Adaptation to natural facial categories. Nature, 428, 557-561, 2004]. In an event-related brain potential (ERP) study, Kovács et al. [Kovács, G., Zimmer, M., Banko, E., Harza, I., Antal, A., & Vidnyanszky, Z. Electrophysiological correlates of visual adaptation to faces and body parts in humans. Cerebral Cortex, 16, 742-753, 2006] reported reduced N170 amplitudes and increased latencies for test faces following female gender adaptation compared to control stimulus (a phase randomized face) adaptation. We examined whether this N170 attenuation to test faces was related to the adaptor's gender, or to adaptation to face exposure in general. We compared N170 effects after adaptation to either male or androgynous faces. Additionally, we investigated cross-modal adaptation for the same test faces following male or androgynous voice adaptors. Visual adaptation to face gender replicated previously reported aftereffects in classifying androgynous faces, and a similar trend was observed following adaptation to voice gender. Strikingly, N170 amplitudes were dramatically reduced for faces following face adaptors (relative to those following voice adaptors), whereas only minimal gender-specific adaptation effects were seen in the N170. By contrast, strong gender-specific adaptation effects appeared in a centroparietal P3-like component (approximately 400-600 msec), which in the context of adaptation may reflect a neural correlate of the detection of perceptual novelty.

Recent findings demonstrate that the perception of other people's eye gaze direction can be dramatically biased by previous adaptation to that gaze direction. Here, we further investigated this aftereffect by examining its development over time, with particular attention to the potential role of the ambiguity of the test stimulus. Following adaptation to gaze to one direction, participants' ability to correctly classify gaze to the adapted direction was severely impaired, both for ambiguous and relatively unambiguous test stimuli. Of particular importance, this aftereffect decreased over time but remained measurable up to 7 minutes post adaptation, with its decline following an exponential decay function. The implications of the present findings are discussed with respect to both coding mechanisms involved in gaze perception and a potential role of adaptation effects in real life situations.

Eye gaze is an important social signal, and humans can accurately determine gaze direction in others. Recently, dramatic adaptation effects on gaze perception were shown, in which the perception of small gaze deviations to the adapted direction is diminished. We compared participants' perceptions of gaze direction before and after adaptation to the left or right gaze, and examined event-related potential correlates of this gaze adaptation. We found a striking impairment in perceiving gaze to the adapted side. Event-related potentials revealed no direction-specific gaze adaptation effects on N170, although small adaptation effects were seen later, approximately 250-350 ms. This suggests that, rather than modulating the gaze processing approximately 170 ms in posterior occipitotemporal areas, adaptation modulates subsequent processes that are possibly mediated by more anterior right-temporal areas.

The face-sensitive N170 is typically enhanced for inverted compared to upright faces. Itier, Alain, Sedore, and McIntosh (2007) recently suggested that this N170 inversion effect is mainly driven by the eye region which becomes salient when the face configuration is disrupted. Here we tested whether similar effects could be observed with non-face objects that are structurally similar to faces in terms of possessing a homogeneous within-class first-order feature configuration. We presented upright and inverted pictures of intact car fronts, car fronts without lights, and isolated lights, in addition to analogous face conditions. Upright cars elicited substantial N170 responses of similar amplitude to those evoked by upright faces. In strong contrast to face conditions however, the car-elicited N170 was mainly driven by the global shape rather than the presence or absence of lights, and was dramatically reduced for isolated lights. Overall, our data confirm a differential influence of the eye region in upright and inverted faces. Results for car fronts do not suggest similar interactive encoding of eye-like features and configuration for non-face objects, even when these objects possess a similar feature configuration as faces.

The use of computer-generated (CG) stimuli in face processing research is proliferating due to the ease with which faces can be generated, standardised and manipulated. However there has been surprisingly little research into whether CG faces are processed in the same way as photographs of real faces. The present study assessed how well CG faces tap face identity expertise by investigating whether two indicators of face expertise are reduced for CG faces when compared to face photographs. These indicators were accuracy for identification of own-race faces and the other-race effect (ORE)–the well-established finding that own-race faces are recognised more accurately than other-race faces. In Experiment 1 Caucasian and Asian participants completed a recognition memory task for own- and other-race real and CG faces. Overall accuracy for own-race faces was dramatically reduced for CG compared to real faces and the ORE was significantly and substantially attenuated for CG faces. Experiment 2 investigated perceptual discrimination for own- and other-race real and CG faces with Caucasian and Asian participants. Here again, accuracy for own-race faces was significantly reduced for CG compared to real faces. However the ORE was not affected by format. Together these results signal that CG faces of the type tested here do not fully tap face expertise. Technological advancement may, in the future, produce CG faces that are equivalent to real photographs. Until then caution is advised when interpreting results obtained using CG faces.