RESUMO
This research examined effects of instruction upon acquisition of Piaget's concept of horizontality and determined sex differences related to this acquisition. Hypotheses tested were that there are no significant differences (a) in performance on perception and prediction tasks, (b) by sex in the ability to comprehend horizontality, (c) by sex in the stage of development after instruction, and (d) by sex after instruction on the number of correct responses on horizontal tasks. Subjects were 18 male and 17 female rural, public school pupils ranging in age from 8 years, 0 months to 9 years, 11 months. Test instruments were a cylindrical bottle half-filled with colored water and eight pictures of bottles positioned at angles from 0 to 315 degrees at increments of 45 degrees. Chi square tests indicated that males performed significantly better than females on perception and prediction, and that instruction significantly improved male performance on prediction and female performance on prediction and perception. It was concluded that females, if given instruction, could more closely approximate the performance of males on the horizontal water level task.