Abstract
The operational momentum effect (OM) indicates an association of mental addition with a rightward spatial bias, whereas subtraction is associated with a leftward bias. To evaluate the assumed attentional origin of the OM effect, we evaluated not only participants’ relative estimation error in a task requiring them to locate addition and subtraction results on a given number line but also their eye-fixation behaviour. Furthermore, to investigate the situatedness of spatial–numerical associations, the orientation of the number line (left-to-right vs. right-to left) was manipulated. OM biases in participants’ explicit number line estimations and more implicit eye-fixation behaviour are integrated into a two-process hypothesis of the OM effect suggesting a first rough spatial anticipation followed by an evaluation/correction process. This account not only is capable of accounting for the results observed for participants’ relative estimation error but is also corroborated by the eye-fixation results. Importantly, the fact that all effects were found independent of the orientation of the number line indicates that spatial–numerical associations such as the OM effect may not be hard-wired associations of spatial and numerical representations but rather reflect influences of situatedness on numerical cognition.
The current research was supported by the Leibniz-Competition Fund (SAW) providing funding to Elise Klein in the funding line “Women in Academic Leadership Positions” [grant number SAW-2014-IWM-4]; and the fortüne program (Forschungsförderung der Tübinger Medizinischen Fakultät) [grant number AZ 2150-1-0].
There are no conflicts of interest associated with this publication, and there has been no significant financial support for this work that could have influenced its outcome. E. Klein and S. Huber contributed equally to this work.