A further parallel between selective adaptation and contrast.

Abstract

It is generally believed that selective adaptation effects in speech perception are due to a reduction in sensitivity of auditory feature detectors. Recent evidence suggest that these effects may derive instead from contrast. In a further test of the contrast hypothesis, we conducted two experiments each involving both adaptation and contrast sessions with matching stimulus sets. During the adaptation sessions of Experiment 1, subjects identified two series of velar stimuli varying in voice onset time, [ga]-[kha] and [gi]-[khi], before and after adaptation with of the following stimuli: [ga], [kha], [gi], and [khi]. In the contrast session, subjects identified either of two ambiguous test items (drawn from near the phonetic boundaries of the [ga]-[kha] and the [gi]-[khi] series) following a single presentation of [ga], [kha], [gi], or [khi]. For both the adaptation and contrast sessions, (a) the [--a] test items were more greatly affected (in a contrast direction) by the [--a] than by the [--i] adaptor/context stimuli, and (b) the [--i] test items were not differentially affected by the [--1] and [--i] adaptor/context stimuli. An analogous design was used in Experiment 2, except that the stimulus sets varied in pitch rather than vowel quality. For both the adaptation and contrast sessions, the test items were not differentially affected by the pitch of the adaptor/context stimulus. These parallel results provide further evidence that adaptation effects are actually a form of contrast.

Audiovisual presentation demonstrates that selective adaptation in speech perception is purely auditory

“…Diehl and his co-workers (e.g., Diehl et al, 1978;Diehl et al, 1980;Elman, 1979) have presented evidence to suggest that the speech adaptation effects typically obtained with procedures similar to that employed here do not reflect fatigue introduced into those sensory processes engaged by an adapting stim…”

“…However, because the effect is not eliminated, a further component remains to be explained. That component could result from the operation of processes such as response biases (Diehl, Elman, & McCusker, 1978;Diehl, Lang, & Parker, 1980), or holistic syllable adaptation (Darwin, 1976), or, indeed, adaptation at a phonetic level of analysis. Alternatively, it may be attributable to the failure to completely eliminate spectrotemporal contiguity between adaptors and testsyllables, The alternative strategy for achievingthe dissociation -that of creating stimuli with identical acoustical specifications that are nonetheless identified in different phonetic categories-has also been explored.…”

“…Here, however, we have argued that adaptation effects cannot be attributed to the perceived phonetic similarity between the adaptor and test syllables. If the proposal of Diehl et al (1978) and Diehl et al (1980) is accepted-that speech adaptation effects and contrast effects reflect the operation of a common process or setof processesthen the failure of a stimulus perceived as [ds] …”

Phonetic Recalibration in Audiovisual Speech

“…Anderen hebben daarentegen beargumenteerd dat selectieve adaptatie mogelijk een relatief simpele criterium verschuiving weerspiegelt (Diehl, 1981;Diehl et al, 1978;Diehl et al, 1980). In tegenstelling tot recalibratie, is selectieve adaptatie niet afhankelijk van een AV conflict maar in plaats daarvan wordt het gehele effect bepaald door het auditieve segment van de stimulus zoals bevestigd in onderzoek naar selectieve adaptatie in AV spraak (Roberts & Summerfield, 1981;Saldaña & Rosenblum, 1994;Shigeno, 2002).…”

A temporally dynamic context effect that disrupts voice onset time discrimination of rapidly successive stimuli

“…Macmillan, Goldberg, and Braida (1988) have argued that some stimuli along a dimension play a special role in providing a reference point that is used in the contextual coding of other stimuli. Both category boundaries (e.g., Diehl, Lang, & Parker, 1980) and prototypes (Samuel, 1982) have been suggested as critical. We chose distance from the categorical /ba/-/pa/ boundary as such a reference point, since Samuel demonstrated that for VOT stimuli like ours, distance from the boundary accounted for se-lective adaptation effects.…”