Neurological impairments of object constancy: The effects of orientation and size disparities

Abstract

Data are reported on the effects of size and orientation disparities in object matching and naming tasks, with five patients whose impaired object constancy has been previously documented (Humphreys & Riddoch, 1984). Only three of the five patients were detrimentally affected by size disparities between prototypical and rotated objects, and none of the patients were affected by disparities between the depicted size of objects and their real-life size. Those patients affected by joint orientation and size disparities appear to have a general deficit in object constancy, apparent whenever there is a large change in the viewpoint–dependent description of an object relative to its prototypical position (e.g. when size disparities are added to orientation disparities). Other patients are more selectively impaired, either by decreases in the saliency of feature information when viewpoint changes, or by problems in deriving orientation information only under particular conditions (such as fore-shortening). The implications of these results for understanding the processes involved in normal object constancy and identification are discussed.