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Several species of animal can count, but only humans can do so using abstract number symbols like ‘2’ or ‘4’. Now we know we do so using a different set of brain cells from those we use to recognise numbers by simply counting groups of objects. This in turn may underpin the unique evolution of mathematical ability in humans.
Evidence for this came from experiments involving nine patients with epilepsy whose brains had temporarily been implanted with electrodes to identify the source of their seizures. While …