Dichotic duplex perception and modularity
Ignatius G. Mattingly · The Journal of the Acoustical Society of America · 1987
Recent work suggests that dichotic duplex perception (in which the same acoustic material simultaneously yields both a phonetic and a nonphonetic percept) occurs when the source-defining or source-localizing processes are given ecologically implausible information, and provides further evidence for the modularity of speech perception. If F3 and F1-F2 of a synthetic syllable are presented dichotically, with identical F0 contours, one hears just the expected syllable at some fixed position within the head. With a somewhat higher F0 contour on F3 than on F1-F2, one hears two voices, one at each ear, both saying the syllable. But with a considerably higher F0 contour on F3, perception is duplex: one hears a buzz at the F3 ear and the syllable at the F1-F2 ear. And if, instead, the basic pattern is modified by shifting F3 abruptly to the F1-F2 ear after 80 ms or more, one hears just the syllable, now moving across the head. But if F3 is shifted sooner, perception is again duplex: one hears a chirp at the ear initially receiving F3 and the syllable at the other ear. Evidently, sufficiently extreme conditions disrupt source definition or source localization without disrupting dichotic speech perception. Speech perception appears to be independent of these other modular processes, and therefore modular itself. [Work supported by NIH Grant HD-1994.]