Reinforced variability decreases with approach to reinforcers

Anticipation of rewards had different effects on operant variability than on operant repetition. We reinforced variable (VAR) response sequences in groups of rats and pigeons and repetitive (REP) response sequences in separate groups. A fixed number of variations or repetitions was required per food reinforcer (e.g., fixed-ratio 4). Although VAR contingencies resulted in high levels of variability and REP contingencies in high repetition, opposite patterns of performance accuracy were observed as rewards were approached. Likelihood of satisfying REP contingencies increased within the fixed ratio, whereas likelihood of satisfying VAR contingencies decreased. These opposite patterns of accuracy were also generated by conditioned reinforcing stimuli correlated with food. Constraints on variability by proximity to reinforcers may explain some detrimental effects of reward.