UNCERTAINTY IN ESTIMATING DISTANCES FROM MEMORY

Magnitude estimations involving spatial characteristics, such as dista nce, typically show a compressive function when estimates are made fro m memory. In particular, as the magnitude of a property grows larger a nd larger, estimates become more and more inaccurate, with increasing underestimates of the actual magnitude. Previous theories have attempt ed to explain this difference by supposing that magnitude estimation w as accomplished through a reperceptual process, in which the errors of perception are magnified, or a transformation process, in which the m emory trace undergoes a consistent alteration toward a more schematic form. The present experiments present evidence in support of an uncert ainty hypothesis. When subjects are uncertain of the actual value of a distance, they are forced to guess on the basis of the mean distance they encountered, because they are unable to retrieve the information accurately. When they can retrieve the information, they are more cert ain and their estimates are more accurate. This hypothesis was also ex tended to integrative conditions in which the subjects were presented with the stimulus display in a piecemeal fashion. In these cases, dist ance estimates were derived by combining spatial representations. This method of presentation caused distance estimates to become less accur ate.