EFFECTS UPON RATS RESPONSES ON A RUNNING WHEEL OF SINGLE ALTERNATION OF LARGE AND SMALL REWARDS AND EXTERNAL CUES

Thirty-two rats were trained to run on a running wheel for one or six pellets of food, in either single alternation (SA) or quasi-random seq uences of reward magnitude and with external cues either informing or not informing the rats of the reward magnitude. Reward-magnitude discr imination was clearly shown when the informative cues were given, but without such cues the SA patterning of responding appeared only late i n training. The reward-magnitude discrimination developed most quickly when internal (SA) cues and external informative cues were both prese nt; the effects of these two classes of cues on discrimination were in teractive rather than additive. Possible explanations are given for th e superior discrimination under the condition where both the internal and external cues were present over the condition when only the extern al cues were present.