Numbers In Our Hands

Main Category: Psychology / Psychiatry
Also Included In: Neurology / Neuroscience
Article Date: 12 May 2008 - 3:00 PDT

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Simple numerical tasks, such as classifying digits as odd or even by pressing left or right buttons, reveal that we like to associate small numbers with left space. Where does this preference come from? Could it reflect the fact we all learned numbers by counting on our fingers? A series of articles in the prestigious neuropsychology journal Cortex investigated links between finger counting and adult numerical cognition with a range of neuroscientific methods. In one behavioural study, Martin Fischer (University of Dundee, Scotland) reports that the majority of adults prefer to start counting on their left hand, regardless of whether they are left- or right-handers. In a subsequent odd-even task, the left-starters had more consistent spatial-numerical associations than the right-starters.This surprising link between finger counting habits and numerical cognition has implications for mathematics teaching and the rehabilitation of people who have lost their number sense.

This study explored the contribution of finger counting habits to the association of numbers with space (the SNARC effect). First, a questionnaire study indicated that two-thirds of 445 adults started counting on their left hand, regardless of their handedness. Secondly, a group of 53 ''left-starters'' but not a group of 47 ''right-starters'' showed a SNARC effect in a parity task. A significant difference in the strength of the effect between groups suggests that finger counting habits indeed contribute to the association between numbers and space in adults.

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