Where is attention while calculating? Evidence from a temporal order judgement task

People often rely on a visuospatial medium to manipulate numbers. Previous studies showed that numbers are generally represented in ascending order on a left-to-right oriented continuum. Because the representation of numbers is spatially oriented, it has been assumed that solving arithmetic problems involves shifting attention toward the side of the continuum where the answer is represented. Based on previous work in neglect patients, we predict that the interaction between mental arithmetic and spatial attention is determined by the relative position of the answer on the visuospatial continuum: subtraction should shift attention leftward because the answer is smaller than the first operand, whereas addition should shift attention rightward because the answer is larger than the operands. In the present study, we used a temporal order judgement task to evidence the attention biases induced by arithmetic operations. Participants had to determine which of a left or right target appeared first on the screen while solving subtraction and addition problems. The left and right targets were flashed with different stimulus onset asynchronies to find the asynchrony at which participants gave an equal proportion of left and right responses. Results showed that this point of subjective simultaneity was larger when participants were solving subtraction problems compared to addition problems, meaning that the right target should be presented several milliseconds in advance to the left target to be perceived as simultaneous during subtraction. This finding indicates that attention was biased to the left side of space during subtraction compared to addition. The just noticeable difference was also larger when participants were solving subtraction problems compared to addition problems, indicating that subtraction decreased sensitivity to temporal asynchronies between the left and right targets. We conclude from these results that mental arithmetic shares common resources with spatial attention.

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Masson, N., Andres, M., Le Maire, P., Alsamour, M., & Pesenti, M. (2016). Where is attention while calculating? Evidence from a temporal order judgement task. IPSY Day- Crossing boundaries, Louvain la Neuve. https://hdl.handle.net/2078.5/185044