The development of hierarchical representation of two-dimensional space.

Adults represent the location of a point in a 2-dimensional space using 2 independent dimensions. They encode location along these dimensions both at a fine-grained level and categorically. In reporting location, they combine and weight the fine-grained and categorical information. In Experiment 1, we found that children as young as 5 years use the same 2 independent dimensions in fine-grained spatial coding of location in a circle as are used by adults-radius and angle. However, categorical coding and hierarchical combination are seen only for radius, at both 5 and 7 years. The adult pattern, where angle as well as radius is coded hierarchically, emerges by 9 years. Experiment 2 shows that there is nothing intrinsically difficult about the categorical coding of angular information; when angle is the only dimension to be encoded, younger children use hierarchical coding. Changes in 2-dimensional hierarchical coding may be due to cognitive load factors and to changes in ability to assign frames of reference.