Differential reinforcing value of speech and heartbeats : a measure of functional lateralization in the neonate

By learning to suck on a nonnutritive nipple in temporal patterns selected by the experimenter, newborns could control whether the sounds of filtered female speech entered their left ear or their right ear. Similarly, other newborns could learn to control whether intrauterine heartbeat sounds entered one ear or the other. Infants consistently learned to suck so as to have speech sounds enter their right ear and heartbeat sounds enter their left ear. The right-ear speech preference and left-ear heartbeat preference in newborns averaging 52 hours of age indicates that auditory perception is functionally lateralized at birth and presumably, therefore, before