Modularity and development: the case of spatial reorientation.

In a series of experiments, young children who were disoriented in a novel environment reoriented themselves in accord with the large-scale shape of the environment but not in accord with nongeometric properties of the environment such as the color of a wall, the patterning on a box, or the categorical identity of an object. Because children's failure to reorient by nongeometric information cannot be attributed to limits on their ability to detect, remember, or use that information for other purposes, this failure suggests that children's reorientation, at least in relatively novel environments, depends on a mechanism that is informationally encapsulated and task-specific: two hallmarks of modular cognitive processes. Parallel studies with rats suggest that children share this mechanism with at least some adult nonhuman mammals. In contrast, our own studies of human adults, who readily solved our tasks by conjoining nongeometric and geometric information, indicated that the most striking limitations of this mechanism are overcome during human development. These findings support broader proposals concerning the domain specificity of humans' core cognitive abilities, the conservation of cognitive abilities across related species and over the course of human development, and the developmental processes by which core abilities are extended to permit more flexible, uniquely human kinds of problem solving.

Mechanisms of reorientation and object localization by children: a comparison with rats.

Neurophysiological studies show that the firing of place and head-direction (HD) cells in rats can become anchored to features of the perceptible environment, suggesting that those features partially specify the rat's position and heading. In contrast, behavioral studies suggest that disoriented rats and human children rely exclusively on the shape of their surroundings, ignoring much of the information to which place and HD cells respond. This difference is explored in the current study by investigating young children's ability to locate objects in a square chamber after disorientation. Children 18-24 months old used a distinctive geometric cue but not a distinctively colored wall to locate the object, even after they were familiarized with the colored wall. Results suggest that the spatial representations underlying reorientation and object localization are common to humans and other mammals. Together with the neurophysiological findings, these experiments raise questions for the hypothesis that hippocampal place and HD cells serve as a general orientation device for target localization.

Internally coherent spatial memories in a mammal.

Children aged 3.5-4.0 years were shown objects being hidden in three different locations in a rectangular environment, were disoriented to disable dead reckoning, and were asked without feedback where each object was. Results showed that children's spatial memories were internally coherents the locations subjects chose were in a correct spatial configuration relative to one another as well as to environmental geometry, despite the fact that the environment's symmetry would have revealed any individual binding of memory for object positions to local environmental features. This finding of internal coherence in the spatial representation of one mammal is discussed relative to neural and behavioral findings on navigation and spatial memory in mammals more generally.

A geometric process for spatial reorientation in young children.

Disoriented rats and non-human primates reorient themselves using geometrical features of the environment. In rats tested in environments with distinctive geometry, this ability is impervious to non-geometric information (such as colours and odours) marking important locations and used in other spatial tasks. Here we show that adults use both geometric and non-geometric information to reorient themselves, whereas young children, like mature rats, use only geometric information. These findings provide evidence that: (1) humans reorient in accord with the shape of the environment; (2) the young child's reorientation system is impervious to all but geometric information, even when non-geometric information is available and is re-presented by the child--such information should improve performance and is used in similar tasks by the oriented child; and (3) the limits of this process are overcome during human development.