Linking numbers to space: from the mental number line towards a hybrid account

Several psychophysical and neuropsychological investigations suggest that the processing of number and spatial information is strongly associated. A popular account for this bulk of evidence argues that this association has its origin in the underlying mental representation of numbers taking the form of a horizontally oriented mental number line, which is isomorphic to the representation of physical lines. Recently however, several alternative explanations have been put forward. We describe those theories and argue that no single current framework is on itself able to explain the full range of observations. To do this, a hybrid account is proposed which takes into account the underlying representation but emphasizes the processing mechanisms required by the task at hand.