A series of experiments were carried out to investigate the effects of training and testing with the frequency, intensity and duration of simple synthetic sounds on the approach behaviour and distress vocalization of young Domestic chickens. Familiar frequencies occurring singly and in combinations can increase the responsiveness of chicks compared with novel frequencies. Neither duration nor intensity appears involved in auditory discrimination learning per se, but rather both allow fine control over the young chick's behaviour. On the basis of comparison with the results of an experiment involving parental calls, the possible structure of a call which would facilitate individual recognition of parents by voice was suggested. Sound frequency may be the most important call parameter facilitating individual recognition of the parental voice by young precocial birds.