The Spatial-Numerical Association of Response Codes (SNARC) effect (Dehaene et al., 1993) is a key phenomenon in numerical cognition. It describes the tendency for individuals to respond faster to smaller numbers with a left-side key and to larger numbers with a right-side key, suggesting a mental mapping of numerical magnitudes onto space. While this effect has been widely replicated, its precise nature remains debated, particularly regarding its task dependency.

 

In this Stage 1 Registered Report, Roth et al. (2025) present a highly powered study that systematically investigates whether the SNARC effect differs in two widely used numerical cognition tasks: magnitude classification (MC) and parity judgment (PJ). In the MC task, participants determine whether a presented number is smaller or larger than a reference value (typically 5). This task explicitly requires magnitude processing, making numerical magnitude directly relevant to the response. In contrast, the PJ task requires participants to judge whether a number is odd or even, a decision that does not explicitly involve numerical magnitude.

 

The authors address a fundamental theoretical question in numerical cognition: while the SNARC effect in PJ is often considered continuous, does it follow a categorical pattern in MC? To investigate this, the study directly compares continuous and categorical representations of the SNARC effect across these two tasks, using Bayesian statistical approaches to determine the best-fitting model. By systematically analysing the SNARC effect in these widely used paradigms, this work aims to refine our understanding of how numerical magnitudes are mapped onto space and whether this mapping depends on task demands. The findings of this study will provide crucial insights into the cognitive mechanisms underlying numerical-spatial associations, highlighting the extent to which task structure shapes the emergence of the SNARC effect.

 

Three expert reviewers provided valuable feedback across multiple rounds of review. Based on ​detailed responses to the reviewers’ and recommender’s comments, the recommender judged that the manuscript met the Stage 1 criteria and therefore awarded in-principle acceptance.​​​

 
URL to the preregistered Stage 1 protocol: https://osf.io/968ad

 

Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly journals:

 

 

 

1. Dehaene, S., Bossini, S., & Giraux, P. (1993). The mental representation of parity and number magnitude. Journal of Experimental Psychology: General, 122(3), 371–396. https://doi.org/10.1037/0096-3445.122.3.371

 

2. Roth, L., Cipora, K., Overlander, A. T., Nuerk, H.-C., & Reips, U.-D. (2025). Shape of SNARC: How task-dependent are Spatial-Numerical Associations? A highly powered online experiment. In principle acceptance of Version 3 by Peer Community in Registered Reports. https://osf.io/968ad