Judgments of horizontality of still water: effects of perceptual and cognitive factors.

Three experiments examined failure to solve the Piagetian water-level horizontality task in terms of artifacts of experimental procedure, perceptual characteristics of the task, and the physical principles involved in the task. The possibility that rotational set accounts for task failure was examined in Exp. 1 (N = 154 college students) with no evidence of an effect, although the spatial tasks used correlated with performance on the horizontality task for women but not for men. In Exp. 2 (N = 159) a procedure of focussing attention on the movement of water and air using a carpenter's level also did not affect horizontality performance. However, Exp. 3 confirmed that performance (N = 57) on the horizontality task was related to understanding the basic principle of the level. These results were discussed in terms of possible experiences of the subjects as well as the relative contributions of perceptual and cognitive factors.