You do not currently have permission to view the full text for this document. Please sign in to an account with an active subscription or contact support.
Methods of quantifying the smiling response of infants are presented and compared. Latency of the smile was found to be the most useful measure, with latency defined as that time from the infant's fixation on a stimulus until a smile of at least one second's duration has occurred. With this measure the peak of the smiling response was found to be between three and one-half months and five months, with an onset between two months and three and one-half months, and a disappearance in the six-to-eight-month range.