The role of meals as a reinforcing event in a token economy programme.

Items such as meals have frequently been used as back-up events in Token Economy Programmes (TEPs) because of their supposed reinforcing effectiveness. However, despite the dubious ethical questions that this raises, there is little research evidence to support the necessity for their use in TEP's with hospitalised chronic mentally ill patients. The effects of introducing meals as a 'free' item on patients' performance of a number of target behaviours were investigated in a TEP where they had previously been scheduled as a back-up event. While 'free' meals produced a slight increase in the actual number of meals eaten, there were no systematic effects on patients' performance of the target behaviours.

Inhibiting function of reinforcement: magnitude effects on variable-interval schedules.

In two experiments, the performance of rats under constant-probability and arithmetic variable-interval schedules respectively was compared when the concentration of a liquid reinforcer was varied within sessions; in other sessions, half of the reinforcers were randomly omitted. When the discriminative function of the reinforcer as a signal for a decrease in the probability of reinforcement was attenuated (the constant-probability schedule) the postreinforcement pause duration was nevertheless an increasing function of reinforcer magnitude. This relationship was also present, but more marked, when the temporal discriminative function of the reinforcer was enhanced (the arithmetic schedule). These results suggested that reinforcement has an unconditioned suppressive effect on the reinforced response distinct from any discriminative function it may acquire. The reinforcement-omission effect, where response rate accelerates following omission, was observed when the reinforcer functioned as an effective temporal discriminative stimulus, but not when such temporal control was absent.

Aftereffects of reinforcement on variable-ratio schedules.

On each of variable-ratio 10, 40, and 80 schedules of reinforcement, when rats' lever-pressing rates were stable, the concentration of a liquid reinforcer was varied within sessions. The duration of the postreinforcement pause was an increasing function of the reinforcer concentration, this effect being more marked the higher the schedule parameter. The running rate, calculated by excluding the postreinforcement pause, was unaffected by concentration. The duration of the postreinforcement pause increased with the schedule parameter, but the proportion of the interreinforcement interval taken up by the pause decreased. Consequently, the overall response rate was an increasing function of the schedule parameter; i.e., it was inversely related to reinforcement frequency, contrary to the law of effect. The running rate, however, decreased with the reinforcement frequency, in accord with the law of effect. When 50% of reinforcements were randomly omitted, the postomission pause was shorter than the postreinforcement pause, but the running rate of responses was not affected.