What's Behind a “+” Sign? Perceiving an Arithmetic Operator Recruits Brain Circuits for Spatial Orienting
Résumé
Do mathematical symbols evoke spatial representations? Although behavioral studies have long demonstrated interactions
between space and the processing of Arabic digits, how to interpret these results remains controversial. Here, we tested
whether activity in regions supporting spatial processing contributes to the processing of symbols conveying fundamental
arithmetic concepts—such as operation signs—even in the absence of associated digits. Using functional magnetic
resonance imaging, we show that merely perceiving a “+” sign triggers activity in brain regions that support the orienting of
spatial attention in adults. Activity in these regions was greater for “+” than for “×” signs, indicating that it is modulated by
whether an operator reflects an operation that evokes numerical manipulation (rather than rote memorization). Finally, the
degree to which subjects activated a spatial region in response to a “+” sign was correlated with the degree to which
subjects benefited from being briefly presented with that sign before having to calculate a single-digit addition problem, an
effect termed operator-priming. Therefore, not only are some arithmetic operators linked to spatial intuitions, but such
intuitions might also have an important role during arithmetic calculation. More generally, our findings support the view
that mathematical symbols inherently evoke spatial representations.