Cross-ear suppression of the verbal transformation effect: Tweaking an acoustic-phonetic level

Abstract

A recorded word repeating over and over undergoes a succession of illusory changes. When two images of the same repeating word are presented dichotically, with a half-cycle delay preventing fusion, the two images of the word each undergo independent illusory transformations at a rate equivalent to that of a single image [Lenz et al., J. Acoust. Soc. Am. 107, 2857 (2000)]. However, with one phoneme difference (e.g., ‘‘dark’’ versus ‘‘dart’’), transition rate is dramatically suppressed [Bashford et al., J. Acoust. Soc. Am. 110, 2658 (2001)]. Rates decrease with extent of feature mismatch at a single phoneme position (roughly 30% reduction with one feature mismatch and 45% with three). Rates also decrease with the number of mismatched phonemes (about 80% rate reduction with three out of four), suggesting a strong acoustic-phonetic basis for verbal transformation suppression. In contrast, semantic relations had no effect (e.g., transformations for ‘‘light’’ were suppressed equally by contralateral night and ‘‘might’’). Dichotic competition appears to allow us to access and selectively influence a prelexical stage of linguistic analysis. [Work supported by NIH.]