Three-month-olds prefer speech to other naturally occurring signals

Human infants show a preference for listening to speech, but little is known about how infants listen to other naturally occurring sounds. Here, we test infants' listening bias for speech against a range of naturally occurring sounds that share properties of speech to varying extents and we aim to better characterize the speech properties that attract infant attention. We compared 3-month-olds' listening patterns for five types of sounds: nonnative speech, rhesus macaque vocalizations, human noncommunicative vocalizations, human communicative nonspeech vocalizations, and environmental sounds. Across three experiments, 3-month-olds preferred speech to the other four types of sounds. The set of acoustic properties we measured-pitch, peak amplitude, nonzero-root mean square amplitude, frequency difference and amplitude variance-did not predict infant looking time. Our results demonstrate that young infants attend selectively to speech over many other naturally occurring stimuli, an important tool for learning language.