Photic reinforcement as a function of optimal level of stimulation

Summary

The concept of an optimal level of stimulation as an explanation for the reinforcing effects of weak light onset was explored in four experiments. Experiment I employed 4 groups of 8 rats each and demonstrated that the Ss would respond at higher levels to obtain weak illumination than to terminate weak illumination. Experiment II involved a group of 8 rats subject to the same level of illumination. By choosing between appropriate levers the animals could either put the test cubicle in darkness for 2 sec. or increase the illumination level for 2 sec. All Ss showed a preference for increasing the illumination. Experiment III introduced a “novelty effect” in that the position of the illumination source changed in response to lever pressing. The Ss’ behavior indicated that this effect was not reinforcing. Experiment IV was designed to study the influence of increased drive on the reinforcing effect of weak light. Results were inconclusive although the trend was in the predicted direction. The ad lib group tended to make more responses to the lever activating the light source than did the deprivation (high drive) group. Results of the four experiments were sufficiently supportive of the hypothesis to suggest that further investigation would be fruitful.