Schedules of aversive stimuli
This chapter shows that substantial control over operant behaviour may be exerted by stimuli such as shock even in the absence of any positive reinforcers such as food. The situations most studied are provided by escape schedules and by avoidance conditions. However, given animals with appropriate experimental histories, schedules of shock presentation also appear capable of maintaining patterns of operant behaviour. In all the experiments reviewed so far, patterns of operant behaviour have been established and maintained by the delivery of reinforcers such as food or water to suitably deprived animals. It has been shown that such behaviour may be considerably affected by also delivering other stimuli, either of a non-aversive kind or of an aversive nature. An operant response may terminate an aversive stimulus which is presented independently of the animal's behaviour. W. N. Schoenfeld's account was offered as an alternative to a theory proposed by H. Mowrer which invoked the concept of 'anxiety' to explain avoidance behaviour.