Infant recognition of infant vocal signals

Most of the speech accessible to infants who are not yet babbling will not have infant vocal properties; yet their perception of infant vocal signals is critical for speech development. We report 3 experiments designed to assess whether 4-to-5-month-olds recognize and preferentially attend to vowels produced by infant talkers over vowels produced by adult talkers. Infants were tested in a sequential preferential looking procedure using isolated vowels synthesized by VLAM. In Experiment 1, infants listened significantly longer to vowels produced by an infant talker than an adult (female). In Experiment 2, infants failed to show any listening preference for infant versus adult vowels synthesized with matching (infant-appropriate) f0 values, suggesting that infants either recognized the un-natural pairing of f0 and formant structure in these adult vowels or are attracted to high f0 values. Failing to support the latter interpretation, infants in Experiment 3 showed no listening preference when presented infant vowels with different (infant-appropriate) f0 values. Together, these findings suggest that young infants recognize the converging vocal (source and filter) properties that specify an adult and an infant talker. These recognition skills appear to be available prior to babbling, and thus are available to support early vocal learning.