Comparative and categorical spatial judgments in the monkey: "high" and "low"

Antonio F. Fortes, Hugo Merchant, Apostolos P. Georgopoulos

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)101-108
Number of pages8
JournalAnimal Cognition
Issue number2
StatePublished - 2004

Bibliographical note

Funding Information:
Acknowledgements This work was supported by United States Public Health Service grant NS17413, the United States Department of Veterans Affairs, and the American Legion Brain Sciences Chair. Animal care conformed to the principles outlined in The Guide for Care and Use of Laboratory Animals (National Institutes for Health publication no. 85–23, revised 1985).


  • Categorization
  • High-low
  • Rhesus monkey
  • Spatial cognition


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