Perception of missing fundamental pitch by 3- and 4-month-old human infants.

A hallmark of complex pitch perception is that the pitch of a harmonic complex is the same whether or not the fundamental frequency is present. By 7 months, infants appear to discriminate on the basis of the pitch of the missing fundamental (MF). Although electrophysiological cortical responses to MF pitch changes have been recorded in infants younger than 7 months, no psychophysical studies have been published. This study investigated the ability of 3- and 4-month-olds to perceive the pitch of MF harmonic complexes based on fundamentals of 160 Hz and 200 Hz using an observer-based method. In experiment I, to demonstrate MF pitch discrimination, 3- and 4-month-olds were required to ignore spectral changes in complexes with the same fundamental and to respond only when the fundamental changed. In experiment II, a 60-260 Hz noise was presented with complexes to mask combination tones at the fundamental frequency. In experiment III, complexes were bandpass filtered with a -12 dB/octave slope to limit use of spectral edge cues and presented with a pink noise to mask all distortion products. Nearly all infants tested categorized complexes by MF pitch in these experiments, suggesting perception of the missing fundamental at 3 months.