Backward interference by tones or noise in pitch perception as a function of practice

In a first experiment, the identification of brief tonal stimuli was unaffected by subsequent presentation of white noise. However, subsequent pure tones, whether central to the stimulus frequencies or remote from them, caused substantial declines in correct identification. Apparent backward masking seems therefore to follow rather than to precede some degree of categorization of the masking stimulus. A second experiment shows that even these effects are temporary. Early masking effects are heavily modified by practice, and are not therefore permanent features of sensory processing. Neither experiment provides support for preperceptual theory.