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Author (up) Fortes, A.F.; Merchant, H.; Georgopoulos, A.P. doi  openurl
  Title Comparative and categorical spatial judgments in the monkey: “high” and “low” Type Journal Article
  Year 2004 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 7 Issue 2 Pages 101-108  
  Keywords Animals; *Classification; Cognition; *Discrimination Learning; Form Perception; Macaca mulatta/*parasitology; Male; *Pattern Recognition, Visual; Semantics; *Space Perception  
  Abstract Adult human subjects can classify the height of an object as belonging to either of the “high” or “low” categories by utilizing an abstract concept of midline that divides the vertical dimension into two halves. Children lack this abstract concept of midline, do not have a sense that these categories are directional opposites, and their categorical and comparative usages of high(er) or low(er) are restricted to the corresponding poles. We investigated the abilities of a rhesus monkey to perform categorical judgments in space. We were also interested in the presence of the congruity effect (a decrease in response time when the objects compared are closer to the category pole) in the monkey. The presence of this phenomenon in the monkey would allow us to relate the behavior of the animal to the two major competing hypotheses that have been suggested to explain the congruity effect in humans: the analog and semantic models. The monkey was trained in delayed match-to-sample tasks in which it had to categorize objects as belonging to either a high or low category. The monkey was able to generate an abstract notion of midline in a fashion similar to that of adult human subjects. The congruity effect was also present in the monkey. These findings, taken together with the notion that monkeys are not considered to think in propositional terms, may favor an analog comparison model in the monkey.  
  Address Brain Sciences Center, Veterans Affairs Medical Center, One Veterans Drive, Minneapolis, MN 55417, USA  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1435-9448 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:15069609 Approved no  
  Call Number Equine Behaviour @ team @ Serial 2531  
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Author (up) Merchant, H.; Fortes, A.F.; Georgopoulos, A.P. doi  openurl
  Title Short-term memory effects on the representation of two-dimensional space in the rhesus monkey Type Journal Article
  Year 2004 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 7 Issue 3 Pages 133-143  
  Keywords Analysis of Variance; Animals; Discrimination Learning/*physiology; Macaca mulatta; Male; Memory, Short-Term/*physiology; Mental Processes/*physiology; Pattern Recognition, Visual/*physiology; Space Perception/*physiology  
  Abstract Human subjects represent the location of a point in 2D space using two independent dimensions (x-y in Euclidean or radius-angle in polar space), and encode location in memory along these dimensions using two levels of representation: a fine-grain value and a category. Here we determined whether monkeys possessed the ability to represent location with these two levels of coding. A rhesus monkey was trained to reproduce the location of a dot in a circle by pointing, after a delay period, on the location where a dot was presented. Five different delay periods (0.5-5 s) were used. The results showed that the monkey used a polar coordinate system to represent the fine-grain spatial coding, where the radius and angle of the dots were encoded independently. The variability of the spatial response and reaction time increased with longer delays. Furthermore, the animal was able to form a categorical representation of space that was delay-dependent. The responses avoided the circumference and the center of the circle, defining a categorical radial prototype around one third of the total radial length. This radial category was observed only at delay durations of 3-5 s. Finally, the monkey also formed angular categories with prototypes at the obliques of the quadrants of the circle, avoiding the horizontal and vertical axes. However, these prototypes were only observed at the 5-s delay and on dots lying on the circumference. These results indicate that monkeys may possess spatial cognitive abilities similar to humans.  
  Address Brain Sciences Center (11B), Veterans Affairs Medical Center, One Veterans Drive, MN 55417, Minneapolis, USA  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1435-9448 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:14669074 Approved no  
  Call Number Equine Behaviour @ team @ Serial 2548  
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