Body Movements Modulate SNARC Effect

Spatial Numerical Association of Response Codes (SNARC) effect, in which people respond faster to small numbers with the left hand and to large numbers with the right hand, had inspired intensive studies on spatial-numerical representation since it was first demonstrated by Dehaene et al (2013). Recent studies also showed that participants generated significantly more small numbers after left head turns than after right head turns. One possible explanation for the head-turn bias to the brain’s internal random number generator is from Embodied Cognition, the idea that human cognition are profoundly shaped by the accumulation of the sensory experience during the interactions between our body and the exterior world. Body movements and sensory processing are closely linked with cognition processing. Head-turning shifts attention to the direction of head-turning and activates corresponding spatial-numerical representation. Head is the key component for high level cognition and it is not surprising that head movements affect high-level processing such as numerical cognition. However, is there a similar role of other body movements on high-level cognition? The present study first investigated whether the hands have the same role as the head on numerical cognition and further investigated whether two simultaneous body movements influence numerical cognition in the same way, especially when involving incongruent directions of body movements (head-left turning plus hand-right turning).Random number generation paradigm was adopted. The numbers generated in left-direction movements and in right-direction movement were analyzed. In experiment1, participants lifted either their left hands or right hands on the side of the body. Compared with the number of small numbers generated in the baseline (when participants kept still), the number of small number generated was greater for left-hand lifting, but smaller for right-hand lifting, showing a SNARC effect. In experiment2, participants did hand-lifting and head-turning movements simultaneously and there was no SNARC effect. In Experiment3, participants moved their hands or heads between left and right direction rhythmically in two separate blocks. In both body movement conditions, more smaller numbers were generated in the left-turning relative to the right-turning, showing a SNARC effect. Experiment4investigate the influence of two simultaneous body movements on number generation. Participants were requested to perform two blocks: congruent and incongruent blocks. In the congruent block, head-turning and hand-turning were in same directions and a SNARC effect occurred, while in the incongruent block, head-turning and hand-turning were in opposite directions (eg. head left-turning plus hand right-turning) and SNARC effect disappeared.The main findings of mis study are:1. More small numbers were generated in the left-turning relative to the right-turning in both hand and head movements, indicating typical SNARC effects. Thus, the hands have the same role as the head on numerical cognition.2. When involving two simultaneous body movements, there was a SNARC effect in the congruent condition while no SNARC effect in the incongruent condition. The results further suggested that embodied cognition does influence the spatial-numerical representation.