Effects of Schedules of Reinforcement on Behavioural Variability

As an extension of Boren, Moerschbaecher, & Whyte, (1978), Experiment 1 was a comparison of schedules of reinforcement on location variability. Hens worked in an operant chamber across five keys that were arranged horizontally. A peck to any key was equally effective. Interval schedules were yoked to ratio schedules. Eight schedules were examined: FR 40, FR 10, FI y-40, FI y-10, VR 40, VR 10, VI y-40 and VI y-10. Location variability was measured as the percentage of switching across keys from within trials, between trials (the reinforced peck location to the first peck location of the following trial), and the number of keys used. It was hypothesised that more variation would occur from schedules with large inter-reinforcer-intervals rather than short, and also that interval schedules would result in more variations than ratio schedules. Hypotheses were not up held, however a correlation of response rate and variability was found. In Experiment 2, six new hens worked on a series of (across session) incrementing DRL schedules, from DRL 0.5-sec to DRL 19.2-sec. Results found no correlation of response rate and variability. However, far more within trial switches were observed in Experiment 2 than Experiment 1, suggesting need for further study.