A Study On The Spatial Representation And Processing Mechanism Of Negative Numbers

The spatial representation of numbers has been the most important area of the investigation on the mechanism of number processing, which is one of the hot research topics. Although lots of studies had investigated the spatial representation of positive numbers, studies which focused on negative numbers were surprisingly rare. Moreover, there were problems, such as improper experimental task or paradigm, and incompatible research results in previous studies on negative numbers. At the same time, the two important debates in negative number processing were not solved yet. The first one was the debate between phylogenetic hypothesis and the ontogenetic hypothesis on the direction of negative numbers representation. Another was the debate between holistic processing and separate processing on the processing of the sign and digit of negative number. Addressing itself to these problems, this study was conducted using the speeded magnitude classification paradigm to further investigate the spatial representation and the mechanism of negative number processing.This study included three experiments. The first experiment which contained one part of positive numbers judgment and another part of negative numbers judgment was aimed at investigating the difference between two types of numbers' processing and the direction of spatial representation for them. The second experiment was aimed at further investigating the direction of negative numbers' spatial representation through a mixed display technique, in which both positive numbers and negative numbers are displayed serially but only negative numbers were targets of magnitude judgment. By this way, the participates were forced to pay attention to the minus sign. The third experiment was aimed at investigating the processing of the sign and digit in negative numbers by adopting the asynchronous display method. There were three display methods: sign and digit were synchronously displayed, sign was displayed first and digit was displayed first.The main findings of this study are as follows:(1) Faster left-side decision for negative numbers with small absolute value and faster right-side decisions for negative numbers with large absolute value, which meant the negative numbers are mapped onto the mental number line according to their absolute instead of numerical value. This result was compatible with the phylogenetic hypothesis.(2) Compared to positive numbers, negative numbers had higher activation thresholds.(3) The sign and the digit of negative numbers can be processed independently, which supported the separate processing view.