Abstract
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.