Control of vocal responding in chickens.

Schedules of reinforcement were shown to control the rate of chirping bychickens in the same way as other motor responses in subhumans. Under a discrimination procedure, chickens responded selectively to the visual stimulus associated with food reinforcement for chirping. Control experiments demonstrated that food influenced the rate of responding because it was presented dependent on the chick's vocalizing and not because it had an innate eliciting or "emotionalizing" power.