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.

Adaptation influences perception not only of simple stimulus qualities such as motion or colour, but also of complex stimuli such as faces. Here we demonstrate contrasting aftereffects of adaptation to facial age. In Experiment 1, participants adapted to either young or old faces, and subsequently estimated the age of morphed test faces with interpolated ages of 30, 40, 50 or 60 years. Following adaptation to old adaptors, test faces were classified as much younger when compared to classifications of the same test faces following adaptation to young faces, which in turn caused subjective test face "aging". These aftereffects were reduced but remained clear even when facial gender changed between adaptor and test faces. In Experiment 2, we induced simultaneous opposite age aftereffects for female and male faces. Overall, these results demonstrate interactions in the perception of facial age and gender, and support dissociable neuronal coding of male and female faces.

While humans use their voice mainly for communicating information about the world, paralinguistic cues in the voice signal convey rich dynamic information about a speaker's arousal and emotional state, and extralinguistic cues reflect more stable speaker characteristics including identity, biological sex and social gender, socioeconomic or regional background, and age. Here we review the anatomical and physiological bases for individual differences in the human voice, before discussing how recent methodological progress in voice morphing and voice synthesis has promoted research on current theoretical issues, such as how voices are mentally represented in the human brain. Special attention is dedicated to the distinction between the recognition of familiar and unfamiliar speakers, in everyday situations or in the forensic context, and on the processes and representational changes that accompany the learning of new voices. We describe how specific impairments and individual differences in voice perception could relate to specific brain correlates. Finally, we consider that voices are produced by speakers who are often visible during communication, and review recent evidence that shows how speaker perception involves dynamic face-voice integration. The representation of para- and extralinguistic vocal information plays a major role in person perception and social communication, could be neuronally encoded in a prototype-referenced manner, and is subject to flexible adaptive recalibration as a result of specific perceptual experience. WIREs Cogn Sci 2014, 5:15-25. doi: 10.1002/wcs.1261 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

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While high-level adaptation to faces has been extensively investigated, research on behavioural and neural correlates of auditory adaptation to paralinguistic social information in voices has been largely neglected. Here we replicate novel findings that adaptation to voice gender causes systematic contrastive aftereffects such that repeated exposure to female voice adaptors causes a subsequent test voice to be perceived as more male (and vice versa), even minutes after adaptation [S.R. Schweinberger et al., (2008), Current Biology, 18, 684-688). In addition, we recorded event-related potentials to test-voices morphed along a gender continuum. An attenuation in frontocentral N1-P2 amplitudes was seen when a test voice was preceded by gender-congruent voice adaptors. Additionally, similar amplitude attenuations were seen in a late parietal positive component (P3, 300-700 ms). These findings suggest that contrastive coding of voice gender takes place within the first few hundred milliseconds from voice onset, and is implemented by neurons in auditory areas that are specialised for detecting male and female voice quality.