Auditory and phonetic processes in place perception for stops

Use of the selective adaptation procedure with speech stimuli has led to a number of theoretical positions with regard to the level or levels of processing affected by adaptation. Recent experiments (i.e., Sawusch & Jusczyk, 1981) have, however, yielded strong evidence that only auditory coding processes are affected by selective adaptation. In the present experiment, a test series that varied along the phonetic dimension of place of articulation for stops ([da]-[ga]) was used in conjunction with a [ska] syllable that shared the phonetic value of velar with the [ga] end of the test series but had a spectral structure that closely matched a stimulus from the [da] end of the series. As an adaptor, the [ska] and Ida] stimuli produced identical effects, whereas in a paired-comparison procedure, the [ska] produced effects consistent with its phonetic label. These results offer further support for the contention that selective adaptation affects only the auditory coding of speech, whereas the paired-comparison procedure affects only the phonetic coding of speech. On the basis of these results and previous place-adaptation results, a process model of speech perception is described.