Discrimination and labeling of noise-buzz sequences with varying noise-lead times: An example of categorical perception

The onset of a noise [0.9-2.1 kHz, 55 dB SPL (A weighted)] preceded that of a buzz [100 Hz, 0.5-3.0 kHz, 70 db SPL (A weighted), 500 msec] by —10 to + 80 msec and both terminated simultaneously. Eight adults discriminated among noise-lead times in an oddity task. in separate sessions, they labeled singly presented stimuli with either of the two responses: “no noise” or “noise.” The results are highly similar to those reported for the categorical perception of synthetic plosive consonants differing in voice-onset time. On the average, discrimination was best across a noise-lead-time boundary of about 16 msec, where labeling also shifted abruptly. These results and those of categorical perception, generally, are interpreted in terms of Weber's law as applied to a single component within a stimulus complex. It is concluded that categorical perception of sounds is not unique to speech and suggested that it may be a general property of sensory behavior.