Infants' intensity discrimination: Spectral profiles

Journal/Book: Infant Behav Develop. 1996; 19: 355 Chestnut St, Norwood, NJ 07648. Ablex Publ Corp. 181-190.

Abstract: Seven-month-old infants' detection of a change in the spectral shape of an auditory stimulus, a task termed profile analysis, was assessed. Such changes are usually described as changes in the quality or timbre of a sound, and it has been suggested that listeners discriminate the quality of vowels and musical instruments by analyzing spectral shapes. In a visually reinforced operant head-turn procedure, infants first learned to discriminate two harmonic complexes that contained the same frequencies. Variations in the relative intensities of those frequencies distinguished the two stimuli: The intensity of successive harmonics either increased (rising spectrum) or decreased (falling spectrum). These sounds were then presented at randomly varying sound pressure levels. This roving stimulus level minimized the usefulness of intensity cues at specific frequencies and forced infants to attend to the entire spectral profile. Although infants' performance on the profile analysis task deteriorated relative to that on the discrimination task, they successfully grouped the stimuli in accordance with their spectral profiles. These results provide evidence that infants, like adults, can perform a profile analysis task but that it is more difficult than a simple discrimination task.

Note: Article MG Clarkson, Georgia State Univ, Dept Psychol, Neuropsychol & Behav Neurosci Program, Univ Plaza, Atlanta, GA 30303 USA

Keyword(s): auditory perception; intensity perception; profile analysis; timbre perception; spectral shape; infants; FREQUENCY RESOLUTION; COMPLEX TONES; PERCEPTION; CHILDREN; ADULTS; CATEGORIES; SIGNALS; MASKING; TIMBER; BAND

Zurück | Weiter