Preferences for constant duration delays and constant sized rewards in human subjects

In four experiments, human subjects played a simple video game in which they chose between two buttons that provided reinforcement either on constant or variable schedules. In one condition of Experiment 1, subjects strongly preferred constant sized rewards over variable sized rewards. In the two other conditions, subjects preferred constant duration delays-to-reinforcement over variable duration delays-to-reinforcement. In Experiment 2, subjects were exposed to different parameters and, in Experiment 3, they were exposed to a modified temporal procedure. In each case, subjects continued to prefer constant sized rewards and constant duration delays. The preference for constant duration delays contradicts analogous research showing that pigeons and rats prefer variable duration delays over constant duration delays. In Experiment 4, we explored this difference by omitting the prompts that segmented the phases of the procedure. Under these conditions, the subjects preferred the variable duration delays. Based on these results, we argue that in the absence of effective signals, both people and animals may be forced to use secondary choice strategies such as a proportional waiting rule. The presence of prompts, however, enables people to segment the choice phase and directly choose between the fixed and variable duration delays.