Effects of qualitatively varied reinforcement on response rate in rats

Abstract

This study compared the effects of constant versus qualitatively varied reinforcers on rate of lever pressing using rats as subjects. In Experiment 1, rats were exposed to a 3-component multiple schedule, in which responses were maintained by variable-interval 60-s schedules of reinforcement. During two constantreinforcer components, either sweetened condensed milk or pellets were delivered. In the varied reinforcer component, milk or pellets were delivered in irregular order. In Experiment 2, lever presses were maintained by a variable-interval 60-s schedule during three session types. In one session type, pellets were delivered. In a second session type, milk was delivered and in the third session type milk or pellets were delivered in irregular order. The type of session was randomly selected at the beginning of each day. In both experiments, response rates maintained by milk were generally higher than response rates maintained by varied reinforcers. Qualitatively different reinforcers do not necessarily maintain higher response rates than those maintained by constant reinforcers. The summative effect of qualitatively different reinforcers on response rates depends on specific experimental arrangements.