Weber's Law influences numerical representations in rhesus macaques (Macaca mulatta)

Abstract

We present the results of two experiments that probe the ability of rhesus macaques to match visual arrays based on number. Three monkeys were first trained on a delayed match-to-sample paradigm (DMTS) to match stimuli on the basis of number and ignore continuous dimensions such as element size, cumulative surface area, and density. Monkeys were then tested in a numerical bisection experiment that required them to indicate whether a sample numerosity was closer to a small or large anchor value. Results indicated that, for two sets of anchor values with the same ratio, the probability of choosing the larger anchor value systematically increased with the sample number and the psychometric functions superimposed. A second experiment employed a numerical DMTS task in which the choice values contained an exact numerical match to the sample and a distracter that varied in number. Both accuracy and reaction time were modulated by the ratio between the correct numerical match and the distracter, as predicted by Weber's Law.

Discrimination and representation of relative numerosity in a bisection task by pigeons

“…This finding contrasts with previous research on numerical bisection with nonhumans, which typically has obtained BPs at the geometric mean (e.g., Fetterman, 1993;Jordan & Brannon, 2006b;Meck & Church, 1983;Roberts, 2005).…”

Numerosity representations in crows obey the Weber–Fechner law

“…For instance, values of 0.51 and 0.60 were obtained for rhesus monkeys using a similar delayed match-to-numerosity task [46]. In a forced-choice delayed match-to-sample protocol, Jordan & Brannon [68] reported Weber fractions of 0.47 and 0.48 for rhesus monkeys. In this study, it was also shown that monkeys improved their precision due to training with decreasing Weber fractions from 0.58 to 0.32.…”

Radial distance determination in the rat vibrissal system and the effects of Weber's law

“…Importantly, Weber's law applies only to the perception of properties that can be described as having a magnitude [40]. Weber's law is a particularly robust psychophysical phenomenon-having been shown to hold in tasks ranging from sensorimotor judgements of weight [39,41] to cognitive tasks involving estimates of the number of objects in a sample [42].…”