Seyll, L. & Content, A.
LCLD, Université libre de Bruxelles, Brussels, Belgium
In two experiments, we assessed the intervention of visuo-spatial attention during the resolution of two forms of mental addition: exact calculation (e.g., 56 + 23 = 79) and approximate calculation (e.g., 56 + 23 is about 80). Participants had to memorize the left or right position of a cue before responding verbally to two-digits addition problems. The allocation of attention to one side of the visual field influenced the resolution of approximate additions but not the resolution of exact additions. This influence resulted in the facilitation of addition problems with a larger second operand (between 30 and 49) following the presentation of a right cue and conversely the facilitation of addition problems with a smaller second operand (between 10 and 29) following the presentation of a left cue. These findings can be interpreted as being the consequence of dynamic shifts on a spatially organized mental representation of numbers in the case of approximate addition. Conversely, exact mental arithmetic would rather entail language and complex calculation strategies involving working memory, which might hide or erase the influence of visuo-spatial attention.