Magnitude shifts spatial attention from left to right in rhesus monkeys as in the human mental number line

Rosa Rugani; Michael L Platt; Yujia Zhang; Elizabeth M Brannon

doi:10.1016/j.isci.2024.108866

Magnitude shifts spatial attention from left to right in rhesus monkeys as in the human mental number line

iScience. 2024 Jan 11;27(2):108866. doi: 10.1016/j.isci.2024.108866. eCollection 2024 Feb 16.

Authors

Rosa Rugani^{1

2}, Michael L Platt^{2

3

4}, Yujia Zhang^{5

6}, Elizabeth M Brannon²

Affiliations

¹ Department of General Psychology, University of Padua, Padua, Italy.
² Department of Psychology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA.
³ Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
⁴ Marketing Department, The Wharton School, University of Pennsylvania, Philadelphia, PA, USA.
⁵ Department of Developmental Psychology and Socialization, University of Padua, Padua, Italy.
⁶ Department of Psychology, The Ohio State University, Columbus, OH 43210, USA.

Abstract

Humans typically represent numbers and quantities along a left-to-right continuum. Early perspectives attributed number-space association to culture; however, recent evidence in newborns and animals challenges this hypothesis. We investigate whether the length of an array of dots influences spatial bias in rhesus macaques. We designed a touch-screen task that required monkeys to remember the location of a target. At test, monkeys maintained high performance with arrays of 2, 4, 6, or 10 dots, regardless of changes in the array's location, spacing, and length. Monkeys remembered better left targets with 2-dot arrays and right targets with 6- or 10-dot arrays. Replacing the 10-dot array with a long bar, yielded more accurate performance with rightward locations, consistent with an underlying left-to-right oriented magnitude code. Our study supports the hypothesis of a spatially oriented mental magnitude line common to humans and animals, countering the idea that this code arises from uniquely human cultural learning.

Keywords: Behavioral neuroscience; Evolutionary biology; Zoology.

Abstract

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