Perceptual information in conservation: effects of screening.

Variations of the screening method developed by Piaget and Frank made it possible to systematically vary the number and type of perceptual cues in the conservation of liquid quantity task. In general, nonconservation increased in kindergartners as the number of cues increased. In contrast, first graders were affected very little by the perceptual conditions. The results suggest that the development of conservation involves several levels, beginning with a concept which can be demonstrated only under facilitating conditions.