Cardiac and respiratory conditioning, differentiation, and extinction in the pigeon

Paired light and foot shock in 12 pigeons rapidly developed acceleratory heart and respiratory conditioned responses. Sensitization and stimulus control birds did not condition. When a different colored stimulus light that was not reinforced was mixed in a random series with the reinforced light, rapid differentiation of both heart and respiratory responses occurred. In most cases neither heart nor respiratory conditioned responses could be extinguished by 100 non-reinforced presentations of the conditioned stimulus.