UBC Theses and Dissertations
Pigeons’ memory for event duration Spetch, Marcia Louise
Pigeon's working memory for event duration was investigated using variations of the delayed matching to sample procedure. When a retention interval of variable length was interposed between the sample and comparison stimuli, pigeons responded as though a long-duration sample had been short after retention intervals of 10 sec or greater. This "choose short" effect occurred reliably in each subject, regardless of whether the subject was naive or experienced, whether the sample durations were represented by food-access or light, or whether a two- or three-choice procedure was used. In order to account for these findings, a "subjective shortening" model of memory for event duration was proposed. According to the model, the choose short effect is produced by a discrepancy between a relatively static reference memory of the sample durations and a dynamic working memory of the sample durations that "shortens" over the retention interval. This discrepancy produces the tendency to respond as though the long sample was short, A number of predictions, derived from the subjective shortening model, were confirmed in subsequent experiments. First, after a long retention interval, the point of subjective equality between the short and long samples shifted to a longer duration. Second, stepwise increases in the retention interval produced a temporary choose short effect, whereas stepwise decreases in the retention interval produced a temporary choose long effect. Third, with extended training at a given retention interval, the choose short and choose long effects diminished and overall accuracy improved. These results provided strong support for the subjective shortening model, whereas they could not be interpreted readily within the context of other conceptualizations of working memory processes.
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