Pigeons' spatial memory: IV. Effects of intertrial interval manipulations on delayed matching of key location.

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Abstract
In experiment 1, the effect of intertrial interval (ITI) duration on pigeons'' delayed matching of key location was investigated. Trials began with a ready stimulus (brief operation of the grain feeder); then, 1 (randomly chosen) key from a 3 .times. 3 matrix was lit briefly as the sample. After a delay (retention interval) of 1, 4 or 8 s the sample key was lit again, along with 1 of the other keys. A peck at the key that had served as the sample (correct comparison) produced food reinforcement, whereas a peck to the incorrect comparison led directly to the ITI. In different sessions, the ITI was 2.5 or 25 s. Matching accuracy was lower at the shorter ITI and was related in a direct linear fashion to the log of the ratio of the ITI to the delay interval. In experiment 2, non-contingent food reinforcement presented during the 25-s ITI lowered matching accuracy. In experiment 3, reinforcement was given for pecking a key (the correct comparison, the incorrect comparison or an irrelevant key for the upcoming trial) presented during the ITI. Relative to trials on which no ITI reinforcement was given, reinforcement for pecking any key had a facilitative rather than a disruptive effect on matching accuracy. The facilitation did not happen when these stimuli occurred without reinforcement during the ITI. These results are discussed in relation to models of spatial memory, in relation to the apparent parallels between processes in delayed matching and classical conditioning, and in relation to the notion that expectancy of reinforcement during the matching trial facilitates accurate choice of the correct key location.