Vice Versa? The bidirectionality and symmetry of associations between size and space in S-R compatibility effects

Abstract

The spatial-numerical association of response codes (SNARC) effect denotes faster and more accurate left responses to small(er) numbers and faster and more accurate right responses to large(r) numbers, as compared to the reverse assignment. The spatial-size association of response codes (SSARC) effect describes a similar observation for physical instead of numerical size: left responses are faster and more accurate to physically small(er) stimuli whereas right responses are faster and more accurate to physically large(r) stimuli, as compared to the reverse assignment. Both compatibility effects thus reveal underlying associations between size and space. The major objectives of the present dissertation, which comprises four studies and seven experiments, were to a) investigate the bidirectionality and symmetry of associations between numerical/physical size and space as they emerge as S-R compatibility effects and b) differentiate between the theories accounting for the effects on the basis of their divergent predictions. To investigate the bidirectionality and symmetry of the SNARC/SSARC effect, we compared the compatibility effect of a regular SNARC/SSARC task with number/size stimuli and location responses to the compatibility effect of a reciprocal SNARC/SSARC task with location stimuli and number/size response. Results concerning the SNARC effect revealed that with numerosity or digit/physical location stimuli and manual or vocal location/number responses, spatial-numerical associations are strongly asymmetrical allowing for the regular but not for the emergence of a reciprocal SNARC effect. However, with verbal number/location stimuli and vocal location/number responses, spatial-numerical associations are bidirectional and symmetrical allowing for a regular and reciprocal SNARC effect of similar size. Results concerning the SSARC effect revealed that with physical size/location stimuli and vocal location/size responses, spatial-size associations are strongly asymmetrical allowing for the regular but not for the emergence of a reciprocal SSARC effect. However, with verbal size/location stimuli and vocal location/size responses, spatial-size associations are bidirectional and symmetrical allowing for a regular and reciprocal SSARC effect of similar size. Thus, most interestingly, for both the SNARC and the SSARC effect, reciprocal effects emerge with verbal location stimuli but not with physical location stimuli. The effect of stimulus mode on the emergence of reciprocal (but not regular) SNARC and SSARC effects points towards some crucial feature of verbal location stimuli in eliciting reciprocal effects. Since in their current form none of the existing theories can explain the complete pattern of results without making additional assumptions, the results underpin the necessity to further develop and advance the theoretical accounts.