Behavioral control by an imprinted stimulus: long-term effects.

Newly hatched ducklings were exposed to imprinting procedures and subsequently trained to peck a key by presenting the imprinting stimulus as the reinforcing (response-contingent) event. Individual ducklings then lived in the apparatus under an arrangement in which each peck produced a 15-sec stimulus presentation. For all ducklings, key-pecks tended to occur in bursts, and as the duckling matured, burst length decreased and the interval between bursts increased. However, even when subjects were 60 days old, some responses still occurred.