Constraints on the Yerkes-Dodson law in skin temperature biofeedback

The purpose of the present experiment was to explore the relationship between motivation and task difficulty during temperature biofeedback. A 2 (task difficulty: decreasing vs. increasing) X 3 (motivation: 0 vs. 25 vs. 50 payment) design was employed. It was hypothesized that a curvilinear function would be obtained in the decrease groups following the Yerkes-Dodson law. Sixty-five subjects were randomly assigned to the six experimental conditions and were trained to increase or decrease their finger temperature. Motivation was manipulated by paying subjects 0, 25, or 50 for every 0.1 degree F they increased their finger temperature over baseline for three days. As predicted, the results are quite compatible with the Yerkes-Dodson law on day one in the decrease conditions. However, as training continued the motivational variable no longer played a significant role in influencing performance, although the curvilinear function was still obtained graphically. It would appear that motivation can play a significant role in a subject's ability to control skin temperature.