Does the magnitude of numbers cause lateral shifts of spatial attention (also taking into account directional counting habits and the speed of reaction times)?

Both single-lab and multilab replication studies have consistently demonstrated that merely seeing small- or large-magnitude Arabic number cues at central fixation does not shift an observer’s attention toward ensuing visual targets into the left and right hemispace, respectively. Other investigations showed no consistent shifts of attention even when, following the detection of lateral targets, participants were asked to process the magnitude of preceding central Arabic cues. Shaki and Fischer (2024) have recently argued that when participants with stable left-to-right (or right-to-left) visual counting habits are asked to detect lateral targets only in trials with small- or large-magnitude cues, that is, are asked to process number magnitude ahead of target detection, then lateral shifts of attention congruent with the magnitudes of the cues and the direction of visual counting habits are observed. Here, we wished to verify this new finding in an adequately large sample of 140 left-to-right counting participants, since exploring and confirming an inherent link between number magnitude processing and spatial attention might have crucial implications in the space–number association functional bases debate. The analyses of reaction times (RTs) showed no evidence of shifts of attention induced by central Arabic cues. No shift was also found when the influence of the speed of RTs was taken into account through RT bin analyses run with vincentization procedure. These results point out that the isolated processing of number magnitude does not inherently entail the activation of a spatial representation of magnitude and the triggering of corresponding shifts of spatial attention along a left-to-right oriented mental number line. This negative evidence indirectly supports alternative views that conceive the space–number association as the product of the concomitant processing of both magnitudes, “small/large,” and spatial codes, “left/right,” in the task at hand.