Nonabstract representation for number - evidence from event-related potentials.

We investigated whether the mental representation of numbers was abstract amodal or modality-dependent by taking N270 as an index, the amplitude that represents the conflict between internal representation and perceptual input. Participants were instructed to justify whether the magnitude of the second number (S2) was similar to that of the preceding number (S1), whereas the surface formats of numbers between S1 and S2 were manipulated. The result indicated that N270 was elicited even when the two numbers were in the same magnitude but displayed in different surface formats. Therefore, our results supported an encoding-complex model for number representations, that is, there are no abstract amodal representations for numbers; instead, they are represented by surface-format-specific codes.