INFANTS PERCEPTION OF PITCH - NUMBER OF HARMONICS

This experiment assessed 7-month-old infants' discrimination of harmon ic complexes containing two, three, or five harmonics. In an operant h ead-turn procedure, infants learned to discriminate between complexes having fundamental frequencies of 160 Hz and 200 Hz. Infants were then presented complexes that contained different-frequency harmonics and were required to categorize them on the basis of their fundamental fre quencies. Finally, the fundamental frequency was removed from the soun ds, and infants were required to categorize them in accordance with th e pitch corresponding to the missing fundamental. Although infants dis criminated all the tonal complexes, they successfully categorized only complexes containing three or five harmonics and failed to categorize the two-harmonic complexes, even when they contained the fundamental frequency. These results suggest that infants' perception of pitch det eriorates as the number of harmonics in a tonal complex decreases. Fur thermore, infants may need more spectral information to perceive pitch than do adults, many of whom hear the pitch of the missing fundamenta l for two-harmonic complexes.