Development of isolation-induced vocal behavior in normal-hearing and deafened guinea pig infants

Infants in many different animal species require auditory information from conspecifics to learn appropriate responses to important environmental and social cues. Isolation calls are emitted by infant guinea pigs in contexts of social separation From their mothers. The aim of the present study was t o examine the ontogeny of the isolation calls in normal-hearing and deafene d infant guinea pigs, From 2 to 40 days postpartum and to determine the rol e of hearing maternal vocalization in infant guinea pig vocal responses in contexts of social proximity and isolation. Female newborn pigmented guinea pigs (Cavia porcellus) were housed with their birth mother and siblings. W ater and dry Food were available ad libitum. One day postpartum, the cochle a of infants in the experimental group was destroyed. The control group con sisted of normal-hearing Female siblings. Vocalizations from infants in the experimental and control groups were recorded for 6 minutes when with the mother before isolation, 6 minutes when alone, and then 6 minutes when with the mother after reunion. Recordings were made 5 days per week from 2 to 4 0 days after birth. The duration of calling was calculated for each 6-minut e period of recording. Results demonstrated that deaf infants vocalize more than normal-hearing infants during social isolation from their mothers. Vo cal activity of isolated deaf and normal-hearing infants decreased substant ially over development, almost disappearing by the end of the study period. These results indicate that maternal vocal behavior modulates the vocal re sponses of guinea pigs early in infant development and supports other evide nce that the guinea pig offers a viable model for investigating audition in deaf and normal-hearing human infants.