Infants’ perception of the pitch of rippled noise

Abstract

Previous research has revealed qualitative parallels between infants’ and adults’ perception of the pitch of the missing fundamental, yet it is unclear whether infants’ performance is quantitatively the same as adults’. To begin to quantify some aspects of infants’ pitch processing, 7-month-old infants’ detection of an iterated rippled noise (IRN) was tested in a conditional head-turn procedure. A 500-ms Gaussian noise was repeated at a rate of 1/s, and infants learned to turn their heads when an IRN (with a delay of 2 ms, no attenuation applied to the delayed signal, and 16 iterations) was presented for 6 s. The parameters of the IRN represented a delay that is in the middle of the ‘‘best’’ pitch range for adults; an attenuation that produces the strongest pitch for adults; and a number of iterations that provides a very clear pitch for adults. Throughout testing the overall stimulus level roved from 63 to 67 dBA (over a background of 28 dBA). All infants reliably detected the introduction of the ripple in the spectrum, indicating that infants, like adults, can detect the pitch of IRN. Future research will address the questions of how well and under what conditions infants can discriminate IRN. [Work supported by NICHD and NIDCD.]