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When December 25th is no longer Christmas day, but '20+5' is still 25

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27.03.2008

In a numerate society like ours, we experience about 1000 numbers an hour (unless we work in a bank or a shop or a laboratory, when it would be higher).

Numbers are therefore so pervasive that we may not notice that we possess quite different types of numerical knowledge. On the one hand, we know lots of arithmetical number facts, such as, eight times seven is 56, or that 56 is larger than 42. On the other hand, we know lots of non-arithmetical number facts, for example, that the Second World War began in 1939; that 9391 is our PIN; that our uncle is 91 years old; that 501’s are jeans and that 747’s are jumbo jets.

In one of the latest issue of Cortex, an international journal devoted to the study of the effects of brain lesions on cognitive functions, Cappelletti and colleagues report on a patient who, following brain damage, has his arithmetical facts entirely preserved but lost his non-arithmetical number facts.

This study investigates encyclopaedic numerical knowledge in a patient with a presumed left temporal dysfunction, associated with temporal lobe epilepsy. Encyclopaedic numbers are those used as nominal labels (such as in ‘British Broadcasting Corporation – BBC 1’ or ‘Levis 501’) to express familiar or historical dates (e.g., our birthday or the French revolution, 1789) and to indicate other general or autobiographical numerical information (e.g., Personal Identification numbers – PINs, post-codes, telephone numbers).

The Authors showed a dissociation between impaired processing of encyclopaedic numbers and preserved processing of non-encyclopaedic numbers (e.g., the larger between 54 and 65 or the result of ‘6 × 9’). This dissociation complements the existing data showing the reverse pattern of performance, namely an advantage for encyclopaedic compared to non-encyclopaedic numbers.

These data add important information on an aspect of numerical processing that has not yet been systematically explored and reinforce the distinction between numerical and non-numerical knowledge in the semantic system.

Dr. Marinella Cappelletti | Source: alphagalileo
Further information: www.ucl.ac.uk

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