Vocal development of 9-month-old babies with cleft palate.

This study compared the prelinguistic vocal development of 9-month-old babies with unrepaired cleft palate (n = 30) and age-matched peers (n = 15). Samples of the babies' spontaneous vocalizations were obtained while they interacted with their primary caregiver during play. The groups were compared on a number of variables including (a) canonical babbling ratios, (b) percentage of babies who reached the canonical babbling stage by 9 months, (c) syllable and segmental aspects of babbling, and (d) vocal frequency. Results indicated that the babies with cleft palate had smaller canonical babbling ratios than their age-matched peers, with just 57% of the babies with cleft palate reaching the canonical babbling stage by 9 months compared to 93% of the noncleft babies. Although syllable types and length were similar for the two groups, differences were noted for consonant characteristics. The babies with cleft palate had smaller consonant inventories, with fewer stops, glides, and velars noted. Glottals occurred more frequently in the vocalizations of the babies with cleft palate. Finally, no statistically significant difference was noted in the number of vocalizations produced by the two groups. Some possible explanations for why babies with cleft palate are delayed in babbling are explored.