STIMULUS DEVALUATION AND EXTINCTION OF CHAIN SCHEDULE PERFORMANCE

Pigeons were trained on a two-component multiple schedule in which eac h separate component consisted of a three-link chain schedule. After i nitial baseline training, the stimuli correlated with the terminal lin ks of each chain were presented in a successive discrimination, with o ne stimulus continuing to be associated with reinforcement while respo nses to the alternative stimulus were extinguished. Subjects were then returned to the original chain schedule, but with extinction in effec t in both components of the multiple schedule. In two separate experim ents, extinction of initial-link responding was not affected by which terminal link had been extinguished during the separate discrimination training, indicating that devaluation of the terminal link was not tr ansmitted directly to the initial link of the chain, There was also no effect of the devaluation procedure during the first session of testi ng on responding in the middle link of the chain, but an effect did de velop with continued extinction of the entire chain when the terminal components were presented during extinction. When the terminal compone nts were omitted, however, the latter effect did not occur. Also, when the terminal link was omitted, extinction occurred more rapidly in th e middle component than in the initial component, indicating a backwar d pattern of extinction.