Judging sine wave stimuli as speech and as nonspeech

Abstract

Interest in the perceptual equivalence of “static” and “dynamic” stimuli spans both speech and nonspeech domains. Previous investigations of speech stimuli have shown that, given matched sets of three‐formant steady‐state vowels and vowels flanked by consonantal transitions, phonetic equivalence is not defined by equal position along the two continua [B. Lindblom and M. Studdert‐Kennedy, J. Acoust. Soc. Am. 42, 830–843 (1967)]. For judgments of relative pitch, on the other hand, ramp tones are judged to be nearly equivalent in pitch to steady‐state tones at their endpoint frequencies [P. T. Brady et al., J. Acoust. Soc. Am. 33, 1357–1362 (1961)]. The present set of experiments demonstrates this difference in categorization of static and dynamic stimuli using a single type of stimulus. Two sets of sine wave stimuli (FLAT/CONTOUR) were constructed by modeling the frequency and relative amplitude characteristics of the aforementioned speech stimuli. When judged in terms of phonetic categories (/ᴜ/ vs /ɪ/), significantly greater proportion of /ᴜ/ judgments were observed for the FLAT than for the CONTOUR continuum. However, when the same two sets of stimuli were judged in terms of relative pitch (HIGH versus LOW), no significant difference in response pattern for the two continua was noted. Thus the experiments demonstrate that two distinct response patterns may be elicited for sine wave stimuli contingent only on the experimenter's instructions. [Work supported by NICHD.]