DEVELOPMENTAL DIFFERENCES IN INFANT ATTENTION TO THE SPECTRAL PROPERTIES OF INFANT-DIRECTED SPEECH

Across several independent studies, infants from a few days to 9 month s of age have shown preferences for infant-directed (ID) over adult-di rected (AD) speech. Moreover, 4-month-olds have been shown to prefer s ine-wave analogs of the fundamental frequency of ID speech, suggesting that exaggerated pitch contours are prepotent stimuli for infants. Th e possibility of similar preferences by 1-month-olds was examined in a series of experiments, using a fixation-based preference procedure. R esults from the first 2 experiments showed that 1-month-olds did not p refer the lower-frequency pitch characteristics of ID speech, even tho ugh 1-month-olds were able to discriminate low-pass filtered ID and AD speech. Since low-pass filtering may have distorted the fundamental f requency characteristics of ID speech, 1-month-olds were also tested w ith sine-wave analogs of the fundamental frequencies of the ID utteran ces. Infants in this third experiment also showed no preference for ID pitch contours. In the fourth experiment, 1-month-olds preferred a na tural recording of ID speech over a version which preserved only its l ower frequency prosodic features. From these results, it is argued tha t, although young infants are similar to older infants in their attrac tion to ID speech, their preferences depend on a wider range of acoust ic features (e.g., spectral structure). It is suggested that exaggerat ed pitch contours which characterize ID speech may become salient comm unicative signals for infants through language-rich, interactive exper iences with caretakers and increased perceptual acuity over the first months after birth.