Abilities in visual perception have received much attention in psychometric studies. Over the years since Spearman first announced the identification of a general factor in intelligence, a number of separate abilities in the realm of visual perception, to some extent independent of general intelligence, have come to be recognized, but research studies have often led to contradictory and confusing conclusions about exactly what abilities exist and how they should be defined and measured. Often these abilities have been discussed under the heading of “spatial ability,” because at least some of them have to do with how individuals deal with materials presented in space – whether in one, two or three dimensions, or with how individuals orient themselves in space. Dimensionality is, of course, an inherent attribute of space as commonly perceived, but it may not be the central attribute that is of concern in spatial ability or visual perception in general. What appears to be of more concern is the fact that objects, forms, or symbols are perceived as laid out in the space presented to the eyes (or in the “mind's eye,” imaginal memory), whether in real-life interactions between the individual and his or her surroundings or in pictorial or printed representations of forms, objects, or text on paper.