Children's representation of spatial boundaries

Finding the way home, orienting into familiar and unfamiliar environments, computing our place and position with reference to internal and external cues are essential everyday tasks for animals. It is generally acknowledged that these tasks are accomplished by the brain by means of the internal formation of complex spatial representation, the so called “cognitive maps”. How the brain can form these cognitive maps is a very debated issue in the field of neuroscience. An important stream of research tried to find out what the main environmental features the brain tends to store while navigating are. In order to investigate this, researchers have observed the behavior of animals after being disoriented in a familiar environment. The reorientation paradigm turned out to be a very interesting tool to study spatial cognition because it allows researchers to figure out which environmental components the animals remember and rely on in order to find their way after they have lost track of their heading and position. Experiments with both human adults, children and nonhuman animals have shown that an important feature of the environment the subjects tend to store to reorient is the geometry of the boundaries’ layout (e.g., room shape). Children from as early as 2 years of age have been shown to be able to use the geometric shape of the spatial layout by searching an object hidden in one corner of a rectangular enclosure both in the correct corner and in its geometric equivalent. But which perceptual and physical factors define spatial boundaries? Which geometric components of boundaries are children most sensitive to? How are the same geometric components used in other spatial tasks such as map reading? In our studies we tried to answer these fundamental questions. In our first study we investigated whether children are sensitive to boundaries that constitute either physical or visual obstacles. To this aim we tested children in a reorientation task with both an arena made up of transparent surfaces and an arena made up of opaque surfaces. By using transparent surfaces, we were able to minimize the visually occlusive component of the boundaries but leave intact its physical component. Opaque boundaries presented, instead, both the visual and physical components. In our second study, we further investigated how does the material and visual appearance of boundaries affect navigation by testing children in an arena made up of 20 closely-aligned objects. In this experiment we made the surfaces visually discontinuous, but the configuration of objects was made sufficiently dense to prevent movement and to underline the geometric structure. In our third study, we asked which components of the Euclidean geometry are children most sensitive to while navigating by geometric boundaries and making a map task. In particular we investigated the use of distance and length both in a reorientation task and a map-placement task. The results showed that important developmental changes occur in children’s representation of spatial boundaries and of their geometric components. In particular children became proficient at using transparent surfaces only at the age of five and they start using boundaries made up of closely- aligned objects at the age of seven. At the same time, we showed that the young children (36 to 42 months) reorient correctly in a disorientation task by using the geometric property of distance, rather than length. The same group of children were shown not to be able to use distance nor length in a map task, while they showed the ability to use angle. These results suggest that not all kinds of boundaries are processed equally by children and that their visual aspect might be more important that their property of being obstacles to movement, particularly early in development. They are important because they inform of which material and physical properties of boundaries children are most sensitive to and they can help understanding how to design and build safe environments for children. Moreover, they suggest the geometric property used by young children to reorient is distance, essentially contributing to the wide debate on how children and animals could solve the reorientation task. Finally, they showed that the use of geometric properties in a reorientation task and in a map task might have two different developmental trajectories, suggesting these two competences might be mediated by two different systems and providing an important insight into the development of geometric competences in children.