Perceptual category learning of photographic and painterly stimuli in rhesus macaques (Macaca mulatta) and humans
- Published
- Accepted
- Subject Areas
- Animal Behavior, Psychiatry and Psychology
- Keywords
- categories, simultaneous chain, rhesus macaques, cognition
- Copyright
- © 2016 Altschul et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2016. Perceptual category learning of photographic and painterly stimuli in rhesus macaques (Macaca mulatta) and humans. PeerJ Preprints 4:e967v3 https://doi.org/10.7287/peerj.preprints.967v3
Abstract
Humans are highly adept at categorizing visual stimuli, but studies of human categorization are typically validated by verbal reports. This makes it difficult to perform comparative studies of categorization using non-human animals. Interpretation of comparative studies is further complicated by the possibility that animal performance may merely reflect reinforcement learning, whereby discrete features act as discriminative cues for categorization. To assess and compare how humans and monkeys classified visual stimuli, we trained 7 rhesus macaques and 41 human volunteers to respond, in a specific order, to four simultaneously presented stimuli at a time, each belonging to a different perceptual category. These exemplars were drawn at random from large banks of images, such that the stimuli presented changed on every trial. Subjects nevertheless identified and ordered these changing stimuli correctly. Three monkeys learned to order naturalistic photographs; four others, close-up sections of paintings with distinctive styles. Humans learned to order both types of stimuli. All subjects classified stimuli at levels substantially greater than that predicted by chance or by feature-driven learning alone, even when stimuli changed one every trial. However, humans more closely resembled monkeys when classifying the more abstract painting stimuli than the photographic stimuli. This points to a common classification strategy in both species, once that humans can rely on in the absence of linguistic labels for categories.
Author Comment
The introduction and discussion were revised to better motivate the design and to more clearly convey the implications of the results.
Supplemental Information
Raw Data & Analysis Script
Raw behavioral data, and RStan analysis script