Interference effects in the conservation of weight

On the assumption that the ability to overcome the effects of interference between the physical properties of an object is a basic component in the acquisition of conservation, we hypothesized that children would tend to negate conservation not only when the form of an object is altered but also when, without deforming the object, one of its properties (e.g., color or temperature) is altered; when variations (e.g., movement or orientation) are introduced into the concrete situation in which weight is exerted; or when other spatial properties (e.g., volume or surface) are made to interact with weight. The results indicate that children up to 8 years of age may have difficulty accepting the conservation of weight even when a transformation does not deform the object and that children up to 13 years may accept the conservation of weight but may find it difficult to explain why an object appears heavier in those instances where weight has to be coordinated with another spatial property. The theoretical implications of these results are discussed.