Two experiments, one with adults and one with children, were conducted to explore further the phenomenon of incentive contrast effects in a situation more analogous to the instrumental conditioning studies with rats than had previously been employed with humans. Subjects (44 adults and 44 children) rolled a marble along an inclined “ straightaway ” and into a goal cup at the end. The adult college students earned points toward their course grade for the completion of each trial, while the children were rewarded with tokens which were exchanged for candy. Both adults and children showed improvement in performance as training progressed, but no effect for reward magnitude was obtained, nor did changes in performance occur with shifts in magnitude of reward.