Abstract
The acquisition of logic involved in the concept of equivalence, and its relationship to attainment of conservation of liquid were studied. Equivalence was operationalized according to set theory model—as relationships characterized by three logical properties of reflexivity (R), symmetry (S), and transitivity (T). Each property was assessed by two procedures. Twenty-eight children (age range 4–0 to 5–5) were administered: (1) Pretest for relational terms, (2) Equivalence Battery, (3) Liquid Conservation Task, (4) Liquid Conservation Task—Reduced saliency condition. The three logical properties (each assessed two ways) do not develop in an invariant ordinal sequence (R S T); however, a “psychometric” order of increasing task difficulty did emerge. For all three abilities, one assessment procedure was consistently easier than the other. A significant positive relationship between age and degree of mastery of equivalence logic was found. In this study, complete mastery of equivalence was a necessary condition for attainment of conservation. The data support the proposition that saliency of perceptual change in a conservation task may be a roadblock to attainment of conservation in some preschool children, indirectly suggesting that mastery of equivalence logic probably is not a sufficient condition for conservation.