Recognition and Knowledge of the Water-Level Principle

Abstract

Piaget and Inhelder showed that children do not realize that the surface of a fluid remains horizontal in a tilted vessel. Several studies have since shown that many adults do not have an adequate concept of the water-level principle. However, in all these studies, drawings of vessels, or other abstract displays, were used. The present experiment is an investigation of whether adults who do not know the water-level principle are able to recognize the correct orientation of a fluid surface in realistic three-dimensional scenes and in cinematographic sequences. It was found that all subjects who could state the principle clearly, could precisely and accurately recognize the correct fluid level. More than half the subjects did not know the principle and all these subjects showed evidence in their judgments of only the crudest perceptual schema.