Piaget's water-level tasks: Performance across the lifespan with emphasis on the elderly

Recognition of the invariance of horizontality is commonly measured by paper-and-pencil forms of Piaget's water-level tasks. Whereas there exist a large body of studies on the performance of children, adolescents, and adults, empirical data of the elderly are still missing. Here, we present the results of a large cross-sectional study comprising N = 1704 participants of 4-95 years of age. Analysis of the influence of subjects' age on the performance on eight water-level tasks revealed that the ability to solve the tasks correctly was nonlinearly related to age, increasing for children and adolescents, peaking in participants of middle age, and decreasing for the elderly. Only for two tasks, depicting bottles nearest to a full upside down position, subjects' sex exerted a significant influence on performance, favouring males. However, females of middle and older age also had lower success rates than males to solve the tasks correctly. Some possible causes of the age-associated decline of performance in the elderly are discussed. (C) 2008 Elsevier Ltd. All rights reserved.