Investigating the Orientation Effect on the Water-Level Task: Who? When? and Why?

Four experiments with adults on Piaget's ( J. Piaget & B. Inhelder, 1956 ) water-level task investigated previous reports that containers tilted at larger angles produce more error than those tilted at smaller angles. Experiment 1 found that this orientation effect occurred in both male and female subjects when the angles were manipulated between subjects but was absent in male subjects when manipulated within subjects. Experiments 2 and 3 indicated that male, and to a lesser degree female subjects, appear to benefit from exposure to easier (less-tilted) stimulus trials and, as a result, perform more accurately on subsequent difficult trials. Experiment 4 implicated mental rotation processes in the orientation effect by demonstrating that accuracy varied as a function of how far subjects needed to mentally rotate the container from its initial position to its test position. A developmental sequence is proposed in which relevant spatial abilities are assumed to facilitate acquisition of the principle that liquids are invariantly horizontal, which in turn leads to more accurate performance on the task. Differences in cognitive strategies may be responsible for the Gender × Orientation interaction observed under some conditions.