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A horse's eye view: size and shape discrimination compared with other mammals.

ABSTRACT: Mammals have adapted to a variety of natural environments from underwater to aerial and these different adaptations have affected their specific perceptive and cognitive abilities. This study used a computer-controlled touchscreen system to examine the visual discrimination abilities of horses, particularly regarding size and shape, and compared the results with those from chimpanzee, human and dolphin studies. Horses were able to discriminate a difference of 14% in circle size but showed worse discrimination thresholds than chimpanzees and humans; these differences cannot be explained by visual acuity. Furthermore, the present findings indicate that all species use length cues rather than area cues to discriminate size. In terms of shape discrimination, horses exhibited perceptual similarities among shapes with curvatures, vertical/horizontal lines and diagonal lines, and the relative contributions of each feature to perceptual similarity in horses differed from those for chimpanzees, humans and dolphins. Horses pay more attention to local components than to global shapes.

SUBMITTER: Tomonaga M

PROVIDER: S-EPMC4685539 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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A horse's eye view: size and shape discrimination compared with other mammals.

Tomonaga Masaki M Kumazaki Kiyonori K Camus Florine F Nicod Sophie S Pereira Carlos C Matsuzawa Tetsuro T

Biology letters 20151101 11

Mammals have adapted to a variety of natural environments from underwater to aerial and these different adaptations have affected their specific perceptive and cognitive abilities. This study used a computer-controlled touchscreen system to examine the visual discrimination abilities of horses, particularly regarding size and shape, and compared the results with those from chimpanzee, human and dolphin studies. Horses were able to discriminate a difference of 14% in circle size but showed worse ...[more]

PMID: 26601679

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Project description:Alternative metrics exist for representing variation in plant body size, but the vast majority of previous research for herbaceous plants has focused on dry mass. Dry mass provides a reasonably accurate and easily measured estimate for comparing relative capacity to convert solar energy into stored carbon. However, from a "plant's eye view", its experience of its local biotic environment of immediate neighbors (especially when crowded) may be more accurately represented by measures of "space occupancy" (S-O) recorded in situ-rather than dry mass measured after storage in a drying oven. This study investigated relationships between dry mass and alternative metrics of S-O body size for resident plants sampled from natural populations of herbaceous species found in Eastern Ontario. Plant height, maximum lateral canopy extent, and estimated canopy area and volume were recorded in situ (in the field)-and both fresh and dry mass were recorded in the laboratory-for 138 species ranging widely in body size and for 20 plants ranging widely in body size within each of 10 focal species. Dry mass and fresh mass were highly correlated (r2 > .95) and isometric, suggesting that for some studies, between-species (or between-plant) variation in water content may be unimportant and fresh mass can therefore substitute for dry mass. However, several relationships between dry mass and other S-O body size metrics showed allometry-that is, plants with smaller S-O body size had disproportionately less dry mass. In other words, they have higher "body mass density" (BMD) - more dry mass per unit S-O body size. These results have practical importance for experimental design and methodology as well as implications for the interpretation of "reproductive economy"-the capacity to produce offspring at small body sizes-because fecundity and dry mass (produced in the same growing season) typically have a positive, isometric relationship. Accordingly, the allometry between dry mass and S-O body size reported here suggests that plants with smaller S-O body size-because of higher BMD-may produce fewer offspring, but less than proportionately so; in other words, they may produce more offspring per unit of body size space occupancy.

Dataset Information

A horse's eye view: size and shape discrimination compared with other mammals.

Publications

A horse's eye view: size and shape discrimination compared with other mammals.

Similar Datasets

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