Trends in Cognitive Sciences
ReviewBeyond the number domain
Section snippets
Universality and domain-specificity
The case that the approximate number system (ANS) is cognitively universal is based on four sources of evidence: cognitive development 1, 2, comparative cognition 3, 4, 5, cross-cultural cognition [6] and neurobiology 7, 8, 9. Collectively, these four types of evidence have established a case for a culturally, developmentally and evolutionarily universal system for representing ‘numbers’ as mental magnitudes. Less clear, however, is whether the neural system supporting the ANS is exclusive for
A primitive system for representing ‘number’
The primary behavioral signature of the ANS is Weber's law (Box 1), which holds universally across species, human development and human cultures 1, 2, 8, 9. For example, when monkeys and college students are tested in the same numerosity comparison and addition tasks, Weber's law similarly predicts their performance 4, 19 (Figure 1). Moreover, numerical discrimination in infancy is reliably predicted by numerical ratio 20, 21, indicating that the behavioral signatures of the ANS emerge within
Cognitive similarities between number and other magnitudes
Magnitude judgments are those that invoke questions such as ‘Which is more?’ or ‘Which is bigger?’ Judgments of this nature can be applied to size, length, time, loudness, number or any uni-dimensional property of an object or set. In fact, several cognitive signatures of magnitude processing are common to numbers and many other quantitative dimensions. The shared cognitive signatures of quantitative judgments implicate both a common mental code for quantitative representation and a common
Neural overlap between number and other magnitudes
Multiple sources of evidence, including neuropsychological and neuroimaging studies of humans in addition to neurophysiological studies of non-human primates, have converged on parietal cortex, particularly the IPS, as a substrate for numerical cognition. Classically, however, parietal cortex is associated with attention, visuo-spatial reasoning and the visual guidance of motor behavior 68, 69, 70. Damage to parietal cortex can lead to hemi-spatial neglect and/or extinction in addition to an
Conclusions
A wealth of empirical data demonstrates that numerical cognition is a primitive system that is shared with other animal species and emerges early in development. These data support the hypothesis that ‘number’ is a fundamental and universal cognitive capacity. Yet, several other cognitive functions for discriminating magnitudes also seem to be widely shared with other species and develop early in ontogeny. These capacities include judgments of size, time, brightness and other continuous
Acknowledgements
We thank Sara Cordes, Emily Hopkins, Melissa Libertus, Brad Mahon, Dustin Merritt, David Paulsen and the members of the Brannon laboratory for comments on this manuscript. This work was supported by an NSF CAREER award and a McDonnell Scholar Award to E.M.B in addition to an NRSA postdoctoral fellowship to J.F.C. We also wish to thank David Van Essen for advice in using Caret (http://brainmap.wustl.edu/caret) to generate Figure 4.
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