Assessment of conservation of number: an attempt to enhance ecological validity and diagnostic sensitivity.

Two procedures were used to assess conservation of number in 56 kindergarten boys and girls. In the Standard condition children responded to the usual verbal questions about number. In the Modified condition the ability to conserve number was inferred from the child's judgments concerning which operations did or did not produce a promised increment in his collection of candies. In comparison to the Standard tests, the latter procedure was intended to be simpler verbally, more motivationally engaging, and more similar to the real-life situations in which children make judgments about quantity. Children performed significantly better in the Modified condition than in the Standard condition, a finding which suggests that the usual tests may not fully capture the child's understanding of number. Performance was also significantly better on tests of identity conservation than on tests of equivalence conservation. This identity-equivalence difference, however, was limited to the Standard condition; the two concepts were of equal difficulty when assessed by means of the Modified procedure.