Ace in the hole: playing cards show the role of order and magnitude in the SNARC effect.

The SNARC effect indicates that numbers are mapped from left to right as in a mental number line. Accumulating evidence suggests that it could be attributed both to the magnitude or to the order of numbers, but the role of these two aspects has not yet been disambiguated since the two are tightly correlated. This study investigated the influence of order and magnitude in the SNARC effect using playing cards as stimuli. While most people organize cards in ascending order (AO), according to the Western reading-writing direction, a minority of people arrange them in descending order (DO). In this regard DO people should spontaneously associate low magnitude cards (e.g., 2) to the right, and high magnitude cards (e.g., 6) to the left. Therefore, in DO individuals, cards’ order would elicit a spatial mapping opposite to the canonical mapping of quantities (i.e., mental number line). In Experiment 1, DO participants performed magnitude classification on simple numerals and on playing cards, showing a regular SNARC effect when classifying numbers and no significant effect when classifying cards. Conversely, in Experiment 2, AO participants showed a regular SNARC effect when classifying both numbers and cards. In Experiment 3, a separate group of DO participants was recruited and tested online to replicate Experiment 1 and clarify the occurrence of spatial associations in card classification. Results indicated that DO participants showed regular SNARC effects both in number and card classification, suggesting that magnitude played a key role overruling the order of cards. This is apparently in contradiction with the view that specific experiences with ordered stimuli should determine the direction of an association.