Magnitude Representation In The Numerical Processing: An ERP Study

Magnitude representation is one of the most important questions in number cognition. There are two opposing views on magnitude representation in the numerical processing. Some researchers assume that numerical processing relies on a single, abstract magnitude representation, that is, the magnitude representation is independent of numerical notations. While others deny the existence of a unitary abstract magnitude representation and argue that magnitude representation is dependent on surface format of numbers. Each hypothesis has received considerable amount of supporting evidence. From the conflicting results, we find that the level of magnitude representation is different in previous studies. Therefore, we suppose the representation of magnitude is influenced by the level of magnitude processing in different tasks. According to this hypothesis, we attempt to further investigate the representation of magnitude by recording event-related potentials, with numerical comparison and addition tasks selected to represent two different levels of magnitude representation.This study included three experiments. Adopting a delayed match-to-sample paradigm, the first experiment investigated whether the representation of magnitude depended on the surface format of the numbers, with the Arabic numbers and non-symbolic dots (similar to those on the faces of a mahjong) selected as materials. In the second experiment, the same materials as the first experiment were used, while a delayed verification task paradigm was adopted, in order to investigate whether the representation of magnitude is independent of numerical notations in arithmetic tasks, such as addition tasks. In the third experiment, the same task paradigm as in the second experiment was adopted while the Arabic numbers, Mandarin numbers and non-symbolic dots were adopted as materials. We further explored whether magnitude was indeed represented in an abstract fashionThe main findings of this study are as follows:(1) The magnitude representation will be influenced by the level of magnitude processing in different tasks. In some tasks accessible to shallow processing, the representation of magnitude depends on the surface format of the numbers. While in other tasks a deep level of processing is needed, magnitude is represented in a single, abstract representation.(2) The single, abstract magnitude code might be in the form of Arabic format or at least close to Arabic format.