What's Behind a “+” Sign? Perceiving an Arithmetic Operator Recruits Brain Circuits for Spatial Orienting

Abstract

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.

Learning to run the number line: the development of attentional shifts during single‐digit arithmetic

“…On the one hand, this suggests that increasing involvement of the MNL for solving arithmetic problems relies on the maturation of cognitive systems more than it relies on an increase in fluency per se. For example, neuroimaging studies have found that arithmetic problem solving relies on a network of brain regions supporting spatial attention 41,36 . However, these mechanisms are slow developing and additional structures might be required in children to learn how to navigate along the MNL 21 .…”

Dissociated Spatial-Arithmetic Associations in Horizontal and Vertical Dimensions

“…Consistent with this model, the neural structures recruited during addition and subtraction could resemble those observed during rightward or leftward eye movement, respectively ( Knops et al, 2009a ). The brain substrates implicated in spatial orienting even activate when an arithmetic operator (e.g., addition sign “+”) is shown ( Mathieu et al, 2017 ). In this account, because arithmetic only hijacks the horizontal-dimension spatial transformation system, the spatial compatibility effect does not extend to the vertical dimension.…”

Number concepts: abstract and embodied

“…Secondly, there is a tendency to point more rightward after additions and more leftward after subtractions (spatial operational momentum-OM; [114,115]). And finally, addition and subtraction operations lead to enhanced perceptual sensitivity in the right and left side of space, respectively [116][117][118][119]. But also outside of SNAs, there are clear links between sensorymotor activities and arithmetic biases, such as making and breaking sets inducing addition and subtraction biases, respectively [120].…”