When combined spatial polarities activated through spatio-temporal asynchrony lead to better mathematical reasoning for addition.

Several recent studies have supported the existence of a link between spatial processing and some aspects of mathematical reasoning, including mental arithmetic. Some of these studies suggested that people are more accurate when performing arithmetic operations for which the operands appeared in the lower-left and upper-right spaces than in the upper-left and lower-right spaces. However, this cross-over Horizontality × Verticality interaction effect on arithmetic accuracy was only apparent for multiplication, not for addition. In these studies, the authors used a spatio-temporal synchronous operand presentation in which all the operands appeared simultaneously in the same part of space along the horizontal and vertical dimensions. In the present paper, we report studies designed to investigate whether these results can be generalized to mental arithmetic tasks using a spatio-temporal asynchronous operand presentation. We present three studies in which participants had to solve addition (Study 1a), subtraction (Study 1b), and multiplication (Study 2) in which the operands appeared successively at different locations along the horizontal and vertical dimensions. We found that the cross-over Horizontality × Verticality interaction effect on arithmetic accuracy emerged for addition but not for subtraction and multiplication. These results are consistent with our predictions derived from the spatial polarity correspondence account and suggest interesting directions for the study of the link between spatial processing and mental arithmetic performances.