Habituation may contribute to within-session decreases in responding under high-rate schedules of reinforcement

Two experiments tested the hypothesis that habituation contributes to within-session decreases in responding. In Experiment 1, rats’ leverpressing was reinforced under a fixed ratio (FR) 4 schedule throughout the baseline sessions. During the dishabituation sessions, the first 21 min and the last 21 min were FR 4; dishabituating events occurred during the middle 3 min. The dishabituating events altered the manner of reinforcer delivery in four different ways. Response rates increased after all dishabituating events. In Experiment 2, rats responded on several FR and variable ratio (VR) schedules. The ratio requirement varied from 3 to 15. Within-session decreases in responding were steeper during FR schedules than during VR schedules. In addition, response rates were well described as linear functions of cumulative number of food pellets eaten within sessions. These results support the habituation hypothesis but do not rule out the possibility that other satiety variables might contribute simultaneously.