Lateral asymmetries in infant melody perception.

Two experiments investigated lateral asymmetries in infants' perception of contour-altered and contour-preserved melody changes. In the first study, 40 infants (8.5 months old) of right-handed parents were trained to respond to binaural melody changes with a head turn toward mechanized toy reinforcers. The subsequent test phase included monaural left-ear and right-ear presentations of the familiar melody and of a changed melody. Infants who heard a contour-altered change showed a left-ear advantage, whereas infants who heard a contour-preserved change showed a right-ear advantage. These effects were replicated with a different set of melodies in the second study. The pattern of lateralization for detection of melody changes in infants of right-handed parents resembles that previously found in right-handed adults and may reflect more general hemispheric processing differences in the early organization of auditory information processing.