Selective anchoring and adaptation of phonetic and nonphonetic continua.

A series of four experiments compared the effects of unequal probability anchoring and selective adaptation on phonetic and nonphonetic judgments. The basic stimulus series was a synthetic stop consonant continuum ranging from /b/ to /d/. On this continuum were superimposed covariations in fundamental frequency, intensity or vowel. In each experiment subjects listened to identical test tapes under two judgment conditions: place of articulation, and pitch or loudness or vowel judgments. The two types of judgment were significantly dissociated under both anchoring and adaptation paradigms, thus demonstrating that the former may be no less selective than the latter. From this and other evidence, it was concluded that the two paradigms are, in principle, equivalent, and that the main factors in speech adaptation effects are peripheral fatigue and central auditory contrast. If the selective processes of fatigue and contrast are taken to reflect functional channels of analysis rather than the operation of feature detectors, the same broad processes can be seen at work in both speech and nonspeech adaptation.