Human performance on a two-alternative rapid-acquisition choice task.

Davison and Baum [Davison, M., Baum, W. M., 2000. Choice in a variable environment: every reinforcer counts. Journal of the Experimental Analysis of Behavior 74, 1-24.] developed a concurrent-schedule procedure where, within each session, different reinforcer ratios were arranged across components separated by brief black-outs. Behaviour adapted quickly to the reinforcer ratios and reinforcers also had local effects on responding. This procedure has been used with pigeons and rats. In the present experiment, we adapted the Davison and Baum procedure to study the effects of reinforcement on human choice behaviour. Eighteen participants were presented with four different reinforcer ratios within a single 50-minute session. Mean sensitivity to the reinforcer ratios increased within components, and preference was greater for the just-reinforced response alternative immediately following reinforcer delivery, similar to the results from non-human experiments. Although there were limitations to the current procedure, the local time scale analyses are a novel way of examining human operant behaviour.