The term functional validation has been used to describe situations in which fully developed behaviours require appropriate environmental support during an early sensitive period if the initial level of responsiveness is to be maintained. The primary objective of the present study was to determine if an age-related decline in responsiveness to the maternal feeding call occurred in Gallus chicks and, if so, whether or not brief exposure to the call during an early responsive period would maintain responsiveness beyond that period. A decline in responsiveness to the call was observed beyond three days of age in dark-reared chicks. Exposure to the call for 7.5 min before three days of age was adequate to maintain responsiveness at five days of age.