Continuous visual properties explain neural responses to nonsymbolic number.

Nonsymbolic number and its continuous visual properties are confounded in everyday life: When number changes, its continuous visual properties also change. It could therefore be efficient to rely on the visual properties to judge number. The current consensus, however, holds that number is processed independent of its visual properties. In this study, we pitched these two opposing theories against each other. We used electroencephalography to look at the components suggested to process number. The first experiment showed that number and visual cues affect the N1 and/or the P2 component. To disentangle number and visual processes, we controlled the visual cues in the second experiment. Now, no number-related effects were present. When the data were reorganized according to visual cue instead of number size, N1 and P2 effects emerged. These results argue against the idea that number is processed independent of its continuous visual variables.

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