Why Spatial-Numeric Associations Aren ’ t Evidence for a Mental Number Line

Abstract

In the well-known SNARC effect, people are shown to be faster at responding to relatively large numbers with their right hands, and to relatively small numbers with their left hands, on magnitude-irrelevant tasks. It is typically assumed that both the SNARC effect and the Simon effectin which right-hand responses are facilitated when stimuli appear on the right-hand sideare explained by spatial mappings of stimulus to response; where the former is the result of representing numbers spatially (i.e. along a mental number line) and mapping right-hand responses to large numbers and left-hand responses to small numbers, and the latter is the result of responding to stimuli on the right side of visual space with the right hand and vice-versa. However, the principle of polarity correspondence can also account for these findings; this theory asserts that in binary representations of dimensions, one pole is dominant and tasks are facilitated when dominant stimulus values are mapped to dominant response values. In previous studies, dominance and spatial mapping have been confounded. The current paper uses non-spatial responses (spoken yes and no responses) to consider whether polarity correspondence can account for the SNARC effect.