ASYMMETRIC HEADTURNING TO SPEECH AND NONSPEECH IN HUMAN NEWBORNS

Functional asymmetries were examined in 59 newborns by recording headt urns from midline to binaurally equivalent sounds. Results showed that robust, asymmetric pattern of headturning occurred in most newborns' responses to binaurally presented unfiltered female speech sounds, wit h increased rightward orientation demonstrated in five replications. F emale speech that was modified by attenuation of frequencies above 500 Hz, as well as speech attenuated below 1500 Hz and above 3000 Hz, res ulted in a significant rightward bias in headturning. In contrast, fem ale speech attenuated below 3500 Hz, and continuous, repetitive stimul i such as heartbeat sounds and phrases of speech repeated at the rate of heartbeat (termed heartspeech), failed to generate the rightward or ientation bias. These results suggest that female speech sounds, parti cularly low-frequency sounds related to the naturally occurring prosod ic characteristics of speech, are a salient class of stimuli for the o rganization of lateral biases in orienting in newborns. (C) 1996 John Wiley & Sons, Inc.