A comparison of methods for estimating directions in egocentric space

A central issue for researchers of human spatial knowledge, whether focused on perceptually guided action or cognitive-map acquisition, is knowledge o f egocentric directions, directions from the body to objects and places. Se veral methods exist for measuring this knowledge. We compared two particula rly important methods, manual pointing with a dial and whole-body rotation (body heading), under various conditions of sensory or memory access to tar gets. In two experiments, blindfolded body rotation resulted in the greates t variability of performance (variable error), while the manual dial result ed in greater consistent bias (constant error). The variability of performa nce with body rotation was no greater than that of the dial when subjects' memory loads for directions to targets was reduced by allowing them to peek at targets in between trials, point to concurrent auditory targets, or poi nt with their eyes open. In both experiments, errors with the manual dial w ere greater for directions to targets that were further from the closest or thogonal axis (ahead, behind, right, left), while errors with body rotation with restricted perceptual access were greater for directions to targets t hat were further from an axis straight ahead of subjects. This suggests tha t the two methods will produce evidence of different organizational framewo rks for egocentric spatial knowledge. Implications for the structures and p rocesses that underlie egocentric spatial knowledge, and are involved in es timating directions, are discussed, as is the value of decomposing absolute errors into variable and constant errors.