ABSTRACT
For Piaget, it all began with measurement. Taking the twentieth century’s new slide-rule for assessing mental capacity ‘psychometrically’, he turned it into an instrument of diagnosis and explanation. It was in the course of administering the Binet-Simon intelligence tests, using the usual criteria (the age at which 50% of children could pass a given test), that Piaget became aware that ‘mistakes’—patterned and interprétable— were as measurable as correct answers and the reasoning behind the child’s response became as important as correctness per se. The measure was no longer a score, but a typical pattern of responding; a typical mode of explanation and justification of the answer. Based now on theoretical rather than on actuarial grounds, new tests specifically designed to amplify and explore these responses were generated by Piaget and his colleagues and were later represented in the major domain-dedicated works on number, space, geometry, logic and so on (Piaget and Szeminska, 1952; Piaget and Inhelder, 1956; Piaget et al., 1960; Inhelder and Piaget, 1964). Thus, for example, the original three-term reasoning test adapted directly from Burt (1919), Edith is fairer than Suzanne; Edith is darker than Lili; Which is the fairest/darkest of the three? (Piaget, 1928), became elaborated subsequently into a set of tests designed to capture the grasp of transitive relations at their earliest point of emergence in the child’s thinking. These were ‘concrete’ tasks such as the famous measuring problem (Piaget, et al., 1960) in which children are required to build a tower equal in size to one which is spatially remote from the one under construction. This relies on the grasp of the principle: if A=B and B=C then A=C, and thus is similar in its formal requirements to the three-term reasoning task. The fact that the concrete task is typically solved at around seven years (by 50% of the group sampled) whilst the linguistic version is solved at around twelve/thirteen years (Piaget, 1928) was less significant than the fact that both reputedly measured the same underlying principle of relation coordination. In this way the test battery was augmented by an explanatory principle which was as much an interpretation of the tests themselves as it was of the child. ‘Measurement’ of intellectual development would never mean the same thing again. The schism was born between the laboratory, with its task analysis, and the ‘field’ of educational and clinical practice with its batteries of tests.
