The psychological representation of speech sounds

Fractal timing of verbal transforms

The paper deals with the timing pattern of perceptual change elicited by multiple repetitions of a syllable (the verbal-transformation effect). We show that the distribution of the dwell time, the time spent perceiving a given phonemic form before switching to another form, obeys a power law with an exponent valued between 1 and 2. This result is robust, occurring for meaningless syllables and for English words of different initial phonemic salience. Experiment 2 demonstrates that subjects are aware of the temporal dynamics of perceptual change. On the basis of these results, it is argued that within this paradigm the notion of a mean dwell time is ill defined and there is apparently no characteristic time scale for perceptual change.

Some factors affecting the perceived ordering of natural speech stimuli

Primary auditory stream segregation--the perceptual segregation of acoustically related elements of a continuous auditory sequence into spatially distinct streams--disrupts recovery of the relative temporal order of repeated sequences of consonant and vowel syllables. Three experiments were performed to determine why the apparent temporal order of natural speech is not similarly disrupted. Exp. 1 (N =24) showed that the disruption is not dependent on repetition of the 32 experimental sequences of consonant and vowel syllables. Exps. 2 (N = 48) and 3 (N = 20) showed that when 4 English monosyllables are used as stimuli and syntactic and intonational structure is present then the temporal integrity of the acoustic signal is preserved perceptually. Despite accurate resolution of order for the 40 experimental sequences, errors of words were common. These errors often imposed a syntactic organization on the resulting sequence.

Some aspects of the psychological representation of speech sounds

If one listens to a meaningless syllable that is repeated over and over, he will hear it undergo a variety of changes that can be described systematically in terms of reorganization of the phones constituting the syllable and changes in a restricted set of phonetic distinctive features. When the repeated syllable is followed by a different syllable but in the same voice, the new (test) syllable will be misperceived in a manner related to the perceptual misrepresentation of the repeated syllable. In the present experiment subjects (N = 24) listened to 72 different experimental sequences of repeated syllables in a male voice followed by test syllables in a female voice. Identification of penultimate and test syllables was independent and in no instance were the phone constituting the syllables reorganized. These results are interpreted as evidence against both auditory and phonetic feature detector theories of speech perception.