Perceiving numerosity does not cause automatic shifts of spatial attention

Michele Pellegrino,Fabio Marson,Mario Pinto,Fabrizio Doricchi,Stefano Lasaponara

doi:10.1007/s00221-021-06185-7

Abstract

It is debated whether the representation of numbers is endowed with a directional-spatial component so that perceiving small-magnitude numbers triggers leftward shifts of attention and perceiving large-magnitude numbers rightward shifts. Contrary to initial findings, recent investigations have demonstrated that centrally presented small-magnitude and large-magnitude Arabic numbers do not cause leftward and rightward shifts of attention, respectively. Here we verified whether perceiving small or large non-symbolic numerosities (i.e., clouds of dots) drives attention to the left or the right side of space, respectively. In experiment 1, participants were presented with central small (1, 2) vs large-numerosity (8, 9) clouds of dots followed by an imperative target in the left or right side of space. In experiment 2, a central cloud of dots (i.e., five dots) was followed by the simultaneous presentation of two identical dot-clouds, one on the left and one on the right side of space. Lateral clouds were both lower (1, 2) or higher in numerosity (8, 9) than the central cloud. After a variable delay, one of the two lateral clouds turned red and participants had to signal the colour change through a unimanual response. We found that (a) in Experiment 1, the small vs large numerosity of the central cloud of dots did not speed up the detection of left vs right targets, respectively, (b) in Experiment 2, the detection of colour change was not faster in the left side of space when lateral clouds were smaller in numerosity than the central reference and in the right side when clouds were larger in numerosity. These findings show that perceiving non-symbolic numerosity does not cause automatic shifts of spatial attention and suggests no inherent association between the representation of numerosity and that of directional space.

Highlights

A central issue in current studies on mathematical cognition is whether the mental representation of numbers is endowed with an inherent spatial component so that, for example, in left-to-right reading cultures smaller numbers are automatically positioned to the left of larger ones on a mental number line (MNL)
The original interpretation of the SNARC (Dehaene et al 1993) was that it arises from the correspondence, or non-correspondence, between the left/right position that numbers would inherently occupy along the MNL and the left/right spatial position of the motor response that is associated with the magnitude or parity of numerical targets
We investigated the presence of the Dots Attentional-SNARC effect by entering individual mean RTs in a numerosity × target side × CTI (400, 750 ms) repeated measures ANOVA

Summary

Introduction

A central issue in current studies on mathematical cognition is whether the mental representation of numbers is endowed with an inherent spatial component so that, for example, in left-to-right reading cultures smaller numbers are automatically positioned to the left of larger ones on a mental number line (MNL). This interpretation has been supplemented and qualified by other proposals (for review of this issue, see Kadosh et al 2008; Wood et al 2008; Fattorini et al 2016; Pinto et al 2019a, b, 2021a) These have emphasised the role played by specific factors in the genesis of the SNARC, like the influence of culturally acquired conceptual polarities that would include congruent concepts like “small” and “left” rather than incongruent ones like “small” and “right” (Proctor and Cho 2006; Gevers et al 2010) and the fact that the SNARC arises at the response-selection level (Keus et al 2005; Gevers et al 2006). These improved interpretations of the SNARC all assume, in line with the original interpretation, that the processing of the magnitude or the parity of a number inherently and automatically activates a corresponding spatial representation of the same number, so that in western cultures, smaller numbers would be automatically mentally placed to the left of larger ones (for a recent computational model sharing the same assumption, see Chen and Verguts, 2010)

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Conclusion