Collateral behavior of the pigeon during conditioned suppression of key pecking.

Ethological recording procedures measured collateral behavior in pigeons whose key-pecking performance was suppressed during a tone that ended with unavoidable electric shock. Independent recordings of gross behavior were made by two observers throughout 60-sec intervals immediately before, during, and after tone presentation. Results indicated significant reductions in the frequency of collateral movements and an increase in the time between successive movements during tone presentations. These effects were observed in all subjects, despite differences in the sequential patterns of behavior. Only partial recovery of the behavior evidenced before tone presentation was found during a 60-sec interval following shock. It was concluded that conditioned suppression procedures caused the bird to "freeze" during tone presentation and in this fashion produced a general inhibitory effect on ongoing overt activity, including key pecking.