The human capacity for mathematics
(May 1999)


A report in Science in early May sheds a fascinating light on how human minds
approach mathematics. The evidence of mathematicians themselves has always
suggested that there are at least two ways of thinking about mathematics,
and this now seems to be confirmed.
Albert
Einstein reported that numerical ideas came to him in ''images, more
or less clear, that 'can reproduce and recombine at will,'' while other
mathematicians report that they process mathematics by way of languagerelated
symbols, or verbal representations of numbers.
It now appears that the visualspatial mode and the linguistic mode of doing
mathematics work together. The authors, from France and the USA, believe
that this finding may help children who struggle with numbers.
Studies of braindamaged patients reveal that some can subtract, through
a nonverbal quantitybased operation, but cannot multiply, which involves
a rote verbal operation, while others can multiply but not subtract. The
new study confirms this twomode theory and locates the point where such
mental activity takes place in the brain.
The method used volunteers who are fluent in both Russian and English, who
were trained in the mathematics needed to solve certain problems, either
in Russian or in English. Then they were tested in one of the two
languages.
Where the task involved an exact problem, like deciding if the sum of 53
and 68 is 121 or 127, the volunteers were slower when they were tested in
the second language, presumably because the problem used the linguistic
mathematical ability. When they were give an approximate mathematical
problem, like deciding if 53 plus 68 is closer to 120 or 150, the volunteers
showed no languagedependent lag in their answers, suggesting that this task
does not involve linguistic mathematical abilities.
This languagebased distinction was also demonstrated in other more complex
mathematical tasks such as addition in bases other than 10, and approximations
of logarithms and square roots. And functional brain imaging techniques showed
that exact calculations lit up the volunteers' left frontal lobe, an area
of the brain known to make associations between words. Mathematical estimation,
on the other hand, involved the left and right parietal lobes, parts of the
brain responsible for visual and spatial representations and also for finger
control.
Perhaps significantly, finger counting is typically an early stage in a child's
learning of exact arithmetic, and the authors point out that both preverbal
human infants and monkeys can
numerically distinguish among small groups of objects. So perhaps this innately
grasped nonverbal sense of quantity, an ability that humans share with other
primates, may be a key part to the power which only humans have, the symbolic
mode of mathematical thought, the ability that allowed Einstein to capture
the whole universe in a single equation.
The findings do not give us a method of selecting children who are ''naturally''
better or worse at mathematics, but they do suggest that
the
impact of education may be more important than any inherited ability.
Key names: Stanislas Dehaene and Elizabeth Spelke.
©WebsterWorld Pty Ltd/contributors 2002
