Four experiments were performed to investigate the responses of neonatal chicks in either a straight runway or an open-field to same-age, conspecific distress and contentment vocalizations over the first several days of post-hatch life. Three hundred forty-eight White Leghorn chicks from either a sample of the Cornell Randombred or Athens Canadian x Cornell Randombred population were tested at 24, 48, 72, 96, and/or 144 hours of age. The effects of intermittent light (Experiment 2) and rearing conditions (Experiments 3 and 4) on chick responsivity to conspecific vocalizations were also examined. The results indicated that contentment vocalization stimulation produced lower approach latencies and higher activity levels than distress vocalization stimulation. Moreover, many of the behavioral responses varied with the age of the birds, however, these relationships were seldom monotonic. In addition, individually reared chicks engaged in much higher levels of activity (lower approach latencies, more contentment peeping, more pecking and more orientation away responses) than socially reared birds. Patterns of behavior associated with the reception of conspecific vocalization stimulation were different from the patterns of behavior associated with the emission of these calls. Speculations concerning the communicative Significance of domestic chick distress and contentment vocalizations were discussed. / Ph. D.