Association for Behavior Analysis International

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.

The independence of dimensions of operant responses by humans was investigated in two experiments using a computerized rectangle drawing task from Ross and Neuringer (2002). Variability on the dimensions of area, shape and location was required for reinforcement for one group (VAR); and variability was not required for the other (YOKE). For all three dimensions, U-values, a measure of variability, were higher for the VAR group than for YOKE group; and the number of trials that met the criteria for reinforcement was higher for the VAR group than for the YOKE group. In Experiment 2, reinforcement was contingent on variability on two dimensions regardless of variability on the third. Participants were divided into three groups; each group had one dimension that was not required to vary. U-values were higher for dimensions when reinforcement was contingent on varying shape and location, or area and location. However, U-values did not differ significantly across dimensions when reinforcement was contingent on varying just area and shape. The results of Experiment 1 and 2 are broadly consistent with those of Ross and Neuringer (2002). The importance of orthogonality of dimensions on this task will be discussed.

Previous research shows that reinforcement of variable responding will facilitate sequence learning in rats (Neuringer, Deiss & Olson, 2000) but may interfere with sequence learning in humans (Maes & van der Goot, 2006). The present study aimed to replicate and extend previous research by assessing the role of behavioral variability in the learning of difficult target sequences across 3 species: humans (n = 60), hens (n = 18) and possums (n = 6). Participants were randomly allocated to one of three experimental conditions (Control, Variable, Any). In the Control conditions sequences were only reinforced if they were the target sequence, in the Variability conditions sequences were concurrently reinforced on a Variable Interval 60-s schedule if the just entered sequence met a variability criterion, and in the Any condition sequences were concurrently reinforced on a Variable Interval 60-s schedule for any sequence entered. The results support previous findings with animals and humans; hens and possums were more likely to learn the target sequence in the Variability condition, and human participants were more likely to learn the target sequence in the Control condition. Possible explanations for differences between the performance of humans and animals on this task will be discussed.