The study investigated the conditions under which the allocentric reference frame of the SNARC effect is activated in the absence of an egocentric reference frame. In Experiment 1, visual images were presented as allocentric reference points to establish the allocentric reference frame. The results showed that the consistency between the image position and responding hand did not significantly affect the SNARC effect. This suggests that the allocentric reference frame was either not activated, or its activation was not strong enough to modulate the SNARC effect. In Experiment 2, a task requiring explicit judgment of image position was added to increase the activation strength of the allocentric reference points. The results indicated that image-hand consistency significantly influenced the SNARC effect: when the image position and responding hand were congruent, the SNARC effect was enhanced, while incongruence led to the complete disappearance of the SNARC effect. This finding demonstrates that, even without explicit manipulations of the egocentric reference frame, task-relevant external spatial cues can still modulate the SNARC effect. This suggests that allocentric reference frames can be activated under conditions with relatively low egocentric involvement. Overall, this study provides new empirical evidence for clarifying the functional mechanisms of different spatial reference frames in the SNARC effect.

numerical spatial representation, SNARC effect, egocentric reference frame, allocentric reference frame