Processing Stage Flexibility Of The SNARC Effect:Task Relevance Or Magnitude Relevance?

Numbers could automatically produce the spatial representation and further affect the spatial judgement.One of the landmark findings of spatial-numerical associations is the spatialnumerical Association of Response Codes effect（SNARC）,which shows that responding to small numbers with left-hand is faster than right-hand and the converse for large numbers.Previous studies usually induce different interference factors to examine whether it affects the SNARC effect to exploring the processing stage of SNARC effect,and further reveal the mechanism of spatial-numerical associations.Two recent studies by Nan et al.（2021）and Yan et al.（2021）used the same experimental paradigm to check whether the SNARC effect occurred in the semantic-representation stage but reached contradictory conclusions,showing that the SNARC effect was influenced by a magnitude Stroop effect in a magnitude comparison task but not by a parity Stroop effect in a parity judgment task and was always influenced by the Simon effect in two tasks.The two studies had two distinct operational factors:the task type（magnitude comparison task or parity judgment task,with the numerical magnitude information task-relevant or task-irrelevant）and the semantic representation stage-related interference information（magnitude or parity Stroop effect,with the interference information magnitude-relevant or magnitude-irrelevant）.To determine which factor influenced the SNARC effect,in the present study,the Stroop effect was switched in the two tasks based on the previous studies.The parity Stroop effect was induced in the magnitude comparison task（experiment la and 1b）and the magnitude Stroop effect was induced in the parity judgement task（experiment 2a and 2b）.The findings of four experiments consistently showed that the SNARC effect was not influenced by the parity Stroop effect in the magnitude comparison task but was influenced by the magnitude Stroop effect in the parity judgment task,besides the SNARC effect was influenced by the Simon effect in both two tasks.Combined with the results of Nan et al.（2021）and Yan et al.（2021）,the findings indicated that regardless of the task type or the task-relevance of numerical magnitude information,magnitude-relevant interference information was the primary factor to affect the SNARC effect,and the SNARC effect may actually occurred in both stimulus representation and response selection stages.Furthermore,this finding provided an empirical basis for a newly proposed two-stage processing model（stage of the spatial representation of magnitude,stage of spatial representation to response selection）,and further suggested that different interference information acting in the two stages might be the core reason for the processing stage flexibility of the SNARC effect.