Within-session patterns of responding with changes in the variability and probability of food delivery

• Published in: Behavioural processes Vol. 39; no. 3; pp. 279 - 289
• Main Authors: Weatherly, Jeffrey N, McSweeney, Frances K, Swindell, Samantha
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.02.1997
• Subjects: Habituation; Interval schedule; Pigeon; Rat; Reinforcement probability; Sensitization; Sensitization; Rat; Pigeon; Reinforcement probability; Interval schedule; Habituation
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/S0376-6357(96)00759-0

The present study was an attempt to determine the factors to which subjects sensitize and/or habituate within experimental sessions. Rats pressed a lever and pigeons pecked a key for food reinforcers delivered during a 60 min session. In experiment 1, subjects initially responded on a simple variable-interval 30 s schedule that consisted of 25 intervals. In subsequent conditions, the number of intervals in the series was decreased until subjects responded on a simple fixed-interval 30 s schedule. In experiment 2, subjects always responded on a variable-interval 15 s schedule that resulted in a stimulus change. The probability that a food reinforcer would accompany the stimulus change varied across conditions. Results showed that within-session patterns of responding did not change for either species with changes in the temporal pattern of reinforcer delivery (experiment 1). The within-session response patterns generally became flatter with decreases in the probability of food delivery for both species (experiment 2). The present results indicate that subjects are sensitizing and/or habituating to the reinforcer itself and/or to some aspect of its delivery. They also help to highlight the strength of sensitization-habituation as an explanation for within-session changes in responding.