Humans think about order and number using a spatial representation, and the orientation of this representation is influenced by learning to read and count in a particular direction. For example, people who read and count from left to right represent small/early items on the left side of space and large/late items on the right side of space. Evidence that pre-verbal children organize order and number spatially raises the possibility that humans are predisposed to organize magnitude and order using space without explicit language training. Nonhuman animals also represent magnitudes and order. I tested the hypothesis that nonhuman primates use spatial representations to code order. I reasoned that if ordering depends on spatial representation then performance on an ordering task would be more impaired when performed concurrently with a spatial memory task than when performed concurrently with a non-spatial visual matching task. Across species and tasks I found that concurrent cognitive load impaired performance, but I did not find that this impairment was especially large with concurrent spatial and ordinal processing. In Manuscript 1, orangutan and chimpanzee performance was generally impaired in all concurrent cognitive load conditions, suggesting that spatial memory, visual memory, and ordering are all supported by a general working memory resource. In Manuscript 2, I tested rhesus monkeys on a similar set of experiments in which an ordering task was embedded within a spatial memory task and a non-spatial visual matching-to-sample task. I again found that spatial memory was impaired under all concurrent cognitive load conditions. Taken together, this set of experiments suggests that there is a domain general working memory resource supporting spatial and visual cognition in apes and monkeys, rather than a resource supporting spatial and ordinal processing specifically.
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About this Dissertation
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