Acquisition and maintenance of autoshaped key pecking by pigeons were studied as a function of the duration of trial and intertrial intervals'. In Experiment 1, trial durations were fixed and intertrial durations were variable. Twenty-five groups of birds were studied at trial durations ranging from 1 to 64 sec and mean intertrial interval durations ranging from 6 to 768 sec. Values were chosen so as to obtain several groups with the same ratio of intertrial interval to trial duration. Ratios ranged from 2:1 to 96:1. Over most durations studied, constant values of the ratio produced an approximately constant number of trials to acquisition. High ratios resulted in faster acquisition than did low ratios. Following acquisition, response rate varied inversely with absolute trial duration. In Experiment 2, intertrial interval as well as trial durations were fixed. Intertrial intervals ranged from 48 to 384 sec, and trial durations ranged from 8 to 32 sec. Trials to acquisition again varied inversely with the ratio of intertrial interval to trial duration. In both experiments, this relationship was well approximated by a single power function. These results are shown to strain several current accounts of the classical conditioning process.

Food-deprived pigeons were given brief meals of grain following the presentation of a light on a response key. Pecking the key had no consequence. Virtually all of the pigeons pecked the ligated key. The number of trials prior to the first peck varied inversely with the value of the mean interval between light onsets. Trials to criterion was a negative power function of the value of the intertrial interval. The addition of a second stimulus, never followed by food, retarded the acquisition of toe keypeck, particularly at short intertrial intervals. During steady state performance, the value of two measures of response strength, rate and probability of responding, increased as a function of the duration of the intertrial interval.

No abstract

In Experiment 1, 8 rats were given training on maze alleys blind at 1 end and a further 8 were given training on alleys open at both ends. On standard closed field test problems, the closed alley group made fewer errors than the open alley group, but showed no shift in the relative daculty of problems permitting direct visual solution.In Experiment 2,lO rats were given standard closed field test problems (white barriers and white maze floor) and another 10 were given the same problems with black barriers and white maze floor. There were no significant differences in errors or in the relative difficulty of problems permitting direct visual solution. It was concluded that rats make negligible use of visual cues to blind alleys in the closed field test situation.