Interactions between perceptual and numerical space

Interactions between numbers and space have become a major issue in numerical cognition; they suggest that numerical representations might be deeply rooted in cortical networks that also subserve spatial cognition. Here, in conditions with a cue, we expected to obtain both the spationumerical interaction between perception and semantics (SNIPS) effect and other numerical effects. In conditions without a cue, we expected to obtain only the other numerical effects, and not the SNIPS effect. By subtracting the results of the latter conditions from those of the former, we expected to obtain a SNIPS effect untainted by the other numerical effects. Using nonspatial verbal response options, we allow the SNIPS effect to emerge, but not the spatial numerical association of response codes (SNARC) effect. A total of 32 naïve, right-handed undergraduates of the Università di Padova (20-28 years of age; 22 women, 10 men) participated for a small fee. We performed repeated measures ANOVAs on the reaction time (RT) data of correct responses after averaging across the counterbalanced response assignments. One subject's responses were excluded because of an unusually high error rate of 10.4%. Of the remaining responses, 0.36% was excluded as premature ) or exceptionally slow. In experiment 2, a total of 16 naïve, right-handed undergraduates of the Università di Padova (20-34 years of age; 11 women, 5 men) participated for a small fee. The responses of 1 male subject were excluded because of an unusually high error rate of 8%. The error rate in the remaining data was 1.6% and correlated positively with RT. No responses were faster than 200 ms or slower than 1,100 ms, but 0.7% of them were excluded because they were more than three standard deviations slower than the condition average.