Does the ATOM (a theory of magnitude) model represent the advance in psychological research?

Time, space and quantity are important aspects of human and animal lives. When analysing the studies, an interaction among these three aspects arises. The relationship between number and space is represented by the so-called SNARC (Spatial-Numerical Association of Response Codes) effect. This effect reflects the association between small numbers (i.e., 1) and the left side of space while large numbers (i.e., 9) are placed in the right side of space. The SNARC effect proves that humans represent numbers along a mental number line with a left-to-right orientation (in Western culture). It has been found that time is linked with spatial representation, showing an experiential relativity of perceived time in humans according to the environmental scale. This finding suggests that time and space can influence each other strongly. Classical models suggest using multiple switches and accumulators so that an organism can quantify time and number simultaneously. More recently these models have been revised to postulate an integration between number and time, lying in the same neural circuits. All these findings are unified in a theory (ATOM model) stating that time, space and quantity are part of a generalized magnitude system in the primates’ brains, where specific cortical areas process these elements of the environment. There is relatively little in the literature on how spatial, numerical and temporal dimensions interact in the cognitive system and on the parallel or hierarchical nature of such interaction. We describe the nature of the ATOM model, analysing how each dimension is associated with other ones. Then we review the studies that have tested the interaction among the three representations. Finally, we suggest some future directions in this research field.