Evidence that adaptation of suppression cannot account for auditory enhancement or enhanced forward masking

Delaying the onset of a signal relative to the onset of a sim ultaneous notched masker often improves the ability of listeners to ‘hear o u t’ the signal at both threshold and suprathreshold levels. Viemeister & Bacon ( J. acoust. Soc. Am. , 71, 1502-1507 (1982)) suggested th at such auditory enhancement effects could be accounted for if the suppression produced by the masker on the signal frequency adapted, thereby releasing the signal from suppression. In support of their hypothesis, Viemeister & Bacon reported that a masker preceded by an enhancer having no com ponent at the signal frequency produced more forward masking than did the masker by itself. Here evidence is provided from five new experiments showing that adaptation of psychophysical two-tone suppression is inadequate to account either for auditory enhancement effects or for the enhanced forward masking demonstrated by Viemeister & Bacon.