A motor theory of speech perception, initially proposed to account for results of early experiments with synthetic speech, is now extensively revised to accommodate recent findings, and to relate the assumptions of the theory to those that might be made about other perceptual modes. According to the revised theory, phonetic information is perceived in a biologically distinct system, a ‘module ’ specialized to detect the intended gestures of the speaker that are the basis for phonetic categories. Built into the structure of this module is the unique but lawful relationship between the gestures and the acoustic patterns in which they are variously overlapped. In consequence, the module causes perception of phonetic structure without translation from preliminary auditory impressions. Thus, it is comparable to such other modules as the one that enables an animal to localize sound. Peculiar to the phonetic module are the relation between perception and production it incorporates and the fact that it must compete with other modules for the same stimulus variations.

Psychophysical phenomena such as categorical perception and the perceptual magnet effect indicate that our auditory perceptual spaces are warped for some stimuli. This paper investigates the effects of two different kinds of training on auditory perceptual space. It is first shown that categorization training using non-speech stimuli, in which subjects learn to identify stimuli within a particular frequency range as members of the same category, can lead to a decrease in sensitivity to stimuli in that category. This phenomenon is an example of acquired similarity and apparently has not been previously demonstrated for a category -relevant dimension. Discrimination training with the same set of stimuli was shown to have the opposite effect: subjects became more sensitive to differences in the stimuli presented during training. Further experiments investigated some of the conditions that are necessary to generate the acquired similarity found in the first experiment. The results of these...

A variety of studies have demonstrated that organizing stimuli into categories can affect the way the stimuli are perceived. We explore the influence of categories on perception through one such phenomenon, the perceptual magnet effect, in which discriminability between vowels is reduced near prototypical vowel sounds. We present a Bayesian model to explain why this reduced discriminability might occur: It arises as a consequence of optimally solving the statistical problem of perception in noise. In the optimal solution to this problem, listeners’ perception is biased toward phonetic category means because they use knowledge of these categories to guide their inferences about speakers ’ target productions. Simulations show that model predictions closely correspond to previously published human data, and novel experimental results provide evidence for the predicted link between perceptual warping and noise. The model unifies several previous accounts of the perceptual magnet effect and provides a framework for exploring categorical effects in other domains.

• Speech perception can be viewed as an interplay between linguistic experience and perceptual biases present in the mammalian auditory system. • As a result of linguistic experience, languages have different mappings between voice-onset-time (VOT) and voicing categories [1]. • In English, [–voice] and [+voice] labial stops have a category boundary at approximately +20 ms VOT. • Young infants [2] and animals [3] also display boundarytype behavior at +20 ms VOT. • Research using a non-speech analogue of VOT, called tone-onset-time (TOT), suggests that there is an underlying auditory basis for the perception of stop consonants based on a threshold for detecting onset asynchronies in the vicinity of +20 ms [4]. • Both young infants [5] and English-speaking adults [4] have two regions of heightened sensitivity near +20 ms TOT. • It would be communicatively advantageous for languages to exploit these regions of heightened sensitivity (also called auditory discontinuities) in their sound inventories by placing stop consonant categories on either side of a discontinuity. • Not all languages exploit these auditory discontinuities (ADs) in their stop consonant categories. • In Spanish, for example, [–voice] and [+voice] labial stops have a category boundary at approximately 0 ms VOT, and the two ADs fall within each of the voicing categories [6]. • The present study addresses the question of whether longterm linguistic experience with VOT categories affects the perception non-speech stimuli that are analogous in their acoustic timing characteristics. • Speakers of two languages, English and Spanish, that differ in their mappings of VOT onto their voicing categories were tested in three perceptual tasks:

Recently, speech researchers have begun to examine the formation of speech sound (phonetic) categories and to analyze the internal structure of the consequent categories. One of the most prominent products of this subfield has been the Perceptual Magnet Effect (PME) and the attendant Native Language Magnet (NLM) theory of Kuhl (1991, 2000). In the present paper, a critical review of the evidence for NLM is offered. Because of concerns about the nature of the stimuli, possible confounds inherent in the empirical procedures and failed replications, it is concluded that there is little positive evidence supporting NLM. However, the goal of uncovering the structures of phonetic categories and mechanisms responsible for those structures remains central to an understanding of language acquisition and speech perception more generally. Data from several empirical paradigms investigating the formation and structure of complex auditory categories are beginning to form a coherent picture of phonetic category acquisition.