The rat approximates an ideal detector of changes in rates of reward: Implications for the law of effect

Rats responded on 2 levers delivering brain stimulation reward on concurren t variable interval schedules. Following many successive sessions with unch anging relative rates of reward, subjects adjusted to an eventual change sl owly and showed spontaneous reversions at the beginning of subsequent sessi ons. When changes in rates of reward occurred between and within every sess ion, subjects adjusted to them about as rapidly as they could in principle do so, as shown by comparison to a Bayesian model of an ideal detector. Thi s and other features of the adjustments to frequent changes imply that the behavioral effect of reinforcement depends on the subject's perception of i ncomes and changes in incomes rather than on the strengthening and weakenin g of behaviors in accord with their past effects or expected results. Model s for the process by which perceived incomes determine stay durations and f or the process that detects changes in rates are developed.