A Shared System of Representation Governing Quantity Discrimination in Canids

Abstract

One way to investigate the evolution of cognition is to compare the abilities of phylogenetically related species. The domestic dog (Canis lupus familiaris), for example, still shares cognitive abilities with the coyote (Canis latrans). Both of these canids possess the ability to make psychophysical “less/more” discriminations of food based on quantity. Like many other species including humans, this ability is mediated by Weber’s Law: discrimination of continuous quantities is dependent on the ratio between the two quantities. As two simultaneously presented quantities of food become more similar, choice of the large or small option becomes random in both dogs and coyotes. It remains unknown, however, whether these closely related species within the same family – one domesticated, and one wild – make such quantitative comparisons with comparable accuracy. Has domestication honed or diminished this quantitative ability? Might different selective and ecological pressures facing coyotes drive them to be more or less able to accurately represent and discriminate food quantity than domesticated dogs? This study is an effort to elucidate this question concerning the evolution of non-verbal quantitative cognition. Here, we tested the quantitative discrimination ability of 16 domesticated dogs. Each animal was given nine trials in which two different quantities of food were simultaneously displayed to them. The domesticated dogs’ performance on this task was then compared directly to the data from 16 coyotes’ performance on this same task reported by Baker et al. (2011). The quantitative discrimination abilities between the two species were strikingly similar. Domesticated dogs demonstrated similar quantitative sensitivity as coyotes, suggesting that domestication may not have significantly altered the psychophysical discrimination abilities of canids. Instead, this study provides further evidence for similar non-verbal quantitative abilities across multiple species.

Number without language: comparative psychology and the evolution of numerical cognition

“…Also the lack of a ratio effect reported in wolves in the range 1-4 is potentially in line with the idea of different ways to process small and large quantities (Utrata et al, 2012). In contrast, data against the existence of a subitizing-like process have been described in primates (Jones and Brannon, 2012;Barnard et al, 2013) and canids (Baker et al, 2012), highlighting that we are still far from solving the question raised by Davis and Perusse regarding whether animals subitize (see also Cutini and Bonato, 2012). Interspecific studies comparing different species (fish: Agrillo et al, 2012;canids: Baker et al, 2012) are also reported in the special topic: in both of these studies similarities among the species are greater than differences, suggesting the existence of similar numerical systems among vertebrates.…”

Numerical assessment in the wild: insights from social carnivores

“…The coyotes performed similarly to the dogs, including exhibiting comparable ratio effects, where the performance of the coyotes increased as the numerical distance increased and the ratio between the quantities decreased. Based on this work and a follow-up study examining quantity discrimination in domestic dogs by Baker et al [58], it appears that domestication did not significantly change quantity discrimination abilities in dogs as compared to coyotes. However, in a study comparing quantity discrimination between wolves and dogs, Range et al [65] found the opposite result.…”

“…Within the Order Carnivora, there are data showing quantity discrimination by members of the Felidae [14,54,55], Canidae [56][57][58][59][60], Ursidae [61], Procyonidae [62], Otariidae [63], and Hyaenidae [15] families. Most of these studies have been conducted with captive animals and have asked test subjects to discriminate between different quantities of food [54,56,57].…”

The impact of emotion on numerosity estimation

“…As the magnitudes become less similar, there is less mental overlap and discrimination improves. Adherence to predictions made by Weber’s Law in both human and non-human animals suggests similar representations of each adherent quantity across species (e.g., Walsh, 2003; Cantlon et al, 2006; Baker et al, 2011, 2012). …”