Contour variables in vocal communication between squirrel monkey mothers and infants.

This study investigates the occurrence and structure of the caregiver call, a form of communication in squirrel monkeys that is almost exclusively infant-directed. Caregiver calls exhibit variability in several acoustic features, most notably pitch range and contour, which are significantly associated with particular contexts of infant care; e.g., nursing or retrieval. The use of caregiver calls by squirrel monkeys is compared to the use of motherese (infant-directed speech) by humans. The possible functional and motivational basis for specific acoustic variables in the caregiver call is discussed.