title: Symbol addition by monkeys provides evidence for normalized quantity coding.
abstract: Weber's law can be explained either by a compressive scaling of sensory response with stimulus magnitude or by a proportional scaling of response variability. These two mechanisms can be distinguished by asking how quantities are added or subtracted. We trained Rhesus monkeys to associate 26 distinct symbols with 0-25 drops of reward, and then tested how they combine, or add, symbolically represented reward magnitude. We found that they could combine symbolically represented magnitudes, and they transferred this ability to a novel symbol set, indicating that they were performing a calculation, not just memorizing the value of each combination. The way they combined pairs of symbols indicated neither a linear nor a compressed scale, but rather a dynamically shifting, relative scaling.
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, MA 02115.
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Livingstone
authors.forename: Warren W
authors.initials: WW
authors.lastname: Pettine
authors.forename: Krishna
authors.initials: K
authors.lastname: Srihasam
authors.forename: Brandon
authors.initials: B
authors.lastname: Moore
authors.forename: Istvan A
authors.initials: IA
authors.lastname: Morocz
authors.forename: Daeyeol
authors.initials: D
authors.lastname: Lee
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002755:Choice Behavior / Q000502:physiology; D007858:Learning / Q000502:physiology*; D008253:Macaca mulatta / Q000502:physiology* / Q000523:psychology*; D008297:Male; D055641:Mathematical Concepts; D008959:Models, Neurological; D008960:Models, Psychological; D012201:Reward
keywords: macaque; normalization; number sense; value coding
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