Spatial ability can be divided into three parts -- spatial visualization, spatial perception and mental rotation. These three aspects are often used by developmental psychologists to explain gender differences in cognitive development and perception. Spatial perception and mental rotation are the methods especially used, as they show greater gender differences in spatial ability. Spatial perception is what enables people to make evaluations about vertical and horizontal directions of objects.
Developmental psychologists from the Pitzer College and University of California Los Angeles (UCLA) found that men perform better at tasks that involve mentally rotating objects. Although men and women are able to perceive objects in one position and still recognize that object when it is rotated to a new position, men are able to perceive this change in position faster than women can. This means that visual spatial skills of males are better developed to perceive changes in angles and the position of objects, compared to female skills.
Piaget's horizontality task involves showing a participant a half-full bottle of water and asking the participant to note the level of water. The participant is then asked to forecast where the water level will be when the bottle is slanted. According to Piaget, by age 12 a person attains the knowledge that the water level remains horizontal. But this realization is perceived later by girls than it is by boys. Studies, such as those done by Sholl M. Jeanne and published in Journal of Experimental Psychology: Learning, Memory, and Cognition on college men and women, show that women usually fail to perceive the surface of water in a tilted water bottle as being horizontal. This means that women have poor horizontality.
Research on gender differences in the spatial ability or the ability to perceive the horizontal dimension of objects has not yet arrived at a single explanation for these differences. One explanation put forward is the effect of socialization, which encourages male children to undertake more tasks such as sports, model building and science-related subjects, all of which enhance spatial abilities. According to an article cited in BBC's "Sex ID; Spatial Ability," testosterone levels in males have also been attributed as a possible explanation of gender differences in spatial ability.