The calibration of walking without vision and the early development of spatial orientation

44 THE CALIBRATION OF WALKING WITHOUT VISION AND THE EARLY DEVELOPMENT OF SPATIAL ORIENTATION John J. Kieser and Anne E. Garing Department of Psychology and Human Development Box 5 12 Peabody, Vanderbilt University Nashville, TN 37203 People can view a target in an open field, close their eyes, and walk to its remembered location accurately. That young children can do this with varying degrees of precision is widely known from watching children’s games like pin-the-tail-on-the-donkey. In order to do this, we suppose children visually perceive their perspective from the starting point; then when blindfolded, they integrate knowledge of the initial perspective with information for selfmovement, in order to keep up-to-date on changes in their perspective relative to the remembered surroundings while walking. But how do children know how far to walk or turn to reach remembered objects - how many steps (and what size) are needed to reach a remembered object that is 3m ahead or 145deg of turn to the left? Knowing this implied calibration of walking activities relative to remembered visually perceived distances and directions. The study of “walking without vision” is a method of investigating age-related changes in the calibration of children’s visuo-motor calibration. This paper presents a series of studies where walking without vision was studied psychophysically for simple translations and simple rotations for young children ranging from 20 to 60 months of age. For translations subjects viewed a target straight ahead at distances ranging from 0.5 to 3m, the room was completely darkened, children walked with the tester in the dark, and then were asked to find the target. The relation of the distance walked relative to the initial target distance was varied systematically. For example, a child seeing a target at lm might then walk 0.5m (in which case he would need to walk further to find it) or 1.5m (in which case he would need to backtrack to find it) across a series of trials to assess whether they could keep track of the distance walked relative to the remembered target distance. The method permits establishment of accuracy thresholds through varying the difference between the visually perceived initial target distance and the walked distance. Even the toddlers showed high levels of success in the task, but their success was strictly limited to the short target distances and in addition, accuracy thresholds improved markedly with age. An analogous method was used for rotations. Subjects viewed a target whose initial direction was varied from trial to trial, the room was completely darkened, the children turned by walking in place with the tester, and then were asked to find the remembered target. The relation of the distance turned relative to the initial target distance or turn was varied systematically. For example, a child seeing a target located 90deg to the right might then turn 45deg (in which case he would need to backtrack to find it). Even the youngest subjects, who were 18 months of age, succeeded on the trials that involved initial target distances of 45deg and 9Odeg turns assessed were 450deg). For rotations, like translations, there were impressive age-related increases in accuracy thresholds and in the distances of oriented walking.