The mismeasure of human part 1 (validity of IQ tests, and the Hereditarian Theory of IQ)

The Hereditarian Theory of IQ

Alfred Binet and the original purposes of the Binet scale 

by: Aria Ratmandanu

            When Alfred Binet (1857-1911), director of the psychology laboratory at the Sorbonne, first decided to study the measurement of intelligence, he turned naturally to the favored method of a waning century and to the work of his great countryman Paul Broca. He set out, in short, to measure skulls, never doubting at first the basic conclusion of Broca's school: 

             The relationship between the intelligence of subjects and the volume of their head . . . is very real and has been confirmed by all methodical investigators, without exception. . . . As these works include observations on several hundred subjects, we conclude that the preceding proposition [of correlation between head size and intelligence] must be considered as incontestable (Binet, 1898, pp. 294-295). 

                  

         Binet went to various schools, making Broca's recommended measurements on the heads of pupils designated by teachers as their smartest and stupidest. In several studies, he increased his sample from 62 to 230 subjects. "I began," he wrote, "with the idea impressed upon me by the studies of so many other scientists, that intellectual superiority is tied to superiority of cerebral volume .

           Binet found his differences, but they were much too small to matter and might only record the greater average height of better pupils (1.401 vs. 1.378 meters). Most measures did favor the better students, but the average difference between good and poor amounted to a mere millimeter—"extremementpetite" as Binet wrote. Binet did not observe larger differences in the anterior region of the skull, where the seat of higher intelligence supposedly lay, and where Broca had always found greatest disparity between superior and less fortunate people. To make matters worse, some measures usually judged crucial in the assessment of mental worth favored the poorer pupils—for anteroposterior diameter of the skull, poorer students exceeded their smarter colleagues by 3.0 mm. Even if most results tended to run in the "right" direction, the method was surely useless for assessing individuals. T h e differences were too small, and Binet also found that poor students varied more than their smarter counterparts. Thus, although the smallest value usually belonged to a poor pupil, the highest often did as well. 

             When Binet returned to the measurement of intelligence in 1904, he remembered his previous frustration and switched to other techniques. He abandoned what he called the "medical" approaches of craniometry and the search for Lombroso's anatomical stigmata, and decided instead on "psychological" methods. The literature on mental testing, at the time, was relatively small and decidedly inconclusive. Galton, without notable success, had experimented with a series of measurements, mostly records of physiology and reaction time, rather than tests of reasoning. Binet decided to construct a set of tasks that might assess various aspects of reasoning more directly.

            In 1904 Binet was commissioned by the minister of public education to perform a study for a specific, practical purpose: to develop techniques for identifying those children whose lack of success in normal classrooms suggested the need for some form of special education. Binet chose a purely pragmatic course. He decided to bring together a large series of short tasks, related to everyday problems of life (counting coins, or assessing which face is "prettier," for example), but supposedly involving such basic processes of reasoning as "direction (ordering), comprehension, invention and censure (correction)" (Binet, 1909). Learned skills like reading would not be treated explicitly. The tests were administered individually by trained examiners who led subjects through the series of tasks, graded in their order of difficulty. Unlike previous tests designed to measure specific and independent "faculties" of mind, Binet's scale was a hodgepodge of diverse activities. He hoped that by mixing together enough tests of different abilities he would be able to abstract a child's general potential with a single score. Binet emphasized the empirical nature of his work with a famous dictum : "One might almost say, 'It matters very little what the tests are so long as they are numerous.' "

           Binet published three versions of the scale before his death in 1911 . The original 1905 edition simply arranged the tasks in an ascending order of difficulty. The 1908 version established the criterion used in measuring the so-called IQ ever since. Binet decided to assign an age level to each task, defined as the youngest age at which a child of normal intelligence should be able to complete the task successfully. A child began the Binet test with tasks for the youngest age and proceeded in sequence until he could no longer complete the tasks. The age associated with the last tasks he could perform became his "mental age," and his general intellectual level was calculated by subtracting this mental age from his true chronological age. Children whose mental ages were sufficiently behind their chronological ages could then be identified for special educational programs, thus fulfilling Binet's charge from the ministry. In 1912 the German psychologist W. Stern argued that mental age should be divided by chronological age, not subtracted from it,* and the intelligence quotient, or IQ, was born.

               IQ testing has had momentous consequences in our century. In this light, we should investigate Binet's motives, if only to appreciate how the tragedies of misuse might have been avoided if its founder had lived and his concerns been heeded. In contrast with Binet's general intellectual approach, the most curious aspect of his scale is its practical, empirical focus. Many scientists work this way by deep conviction or explicit inclination. They believe that theoretical speculation is vain and that true science progresses by induction from simple experiments pursued to gather basic facts, not to test elaborate theories. But Binet was primarily a theoretician. He asked big questions and participated with enthusiasm in the major philosophical debates of his profession. He had a long-standing interest in theories of intelligence. He published his first book on the "Psychology of Reasoning" in 1886, and followed in 1903 with his famous "Experimental Study of Intelligence," in which he abjured previous commitments and developed a new structure for analyzing human thinking. Yet Binet explicitly declined to award any theoretical interpretation to his scale of 

        Intelligence, the most extensive and important work he had done in his favorite subject. Why should a great theoretician have acted in such a curious and apparently contradictory way ? 

            Binet did seek "to separate natural intelligence and instruction in his scale: "It is the intelligence alone that we seek to measure, by disregarding in so far as possible, the degree of instruction which the child possesses. . . . We give him nothing to read, nothing to write, and submit him to no test in which he might succeed by means of rote learning. "It is a specially interesting feature of these tests that they permit us, when necessary, to free a beautiful native intelligence from the trammels of the school. Yet, beyond this obvious desire to remove the superficial effects of clearly acquired knowledge, Binet declined to define and speculate upon the meaning of the score he assigned to each child. Intelligence, Binet proclaimed, is too complex to capture with a single number. This number, later called IQ, is only a rough, empirical guide constructed for a limited, practical purpose: 

            The scale, properly speaking, does not permit the measure of the intelligence, because intellectual qualities are not superposable, and therefore cannot be measured as linear surfaces are measured. 

            Moreover, the number is only an average of many performances, not an entity unto itself. Intelligence, Binet reminds us, is not a single, scalable thing like height. "We feel it necessary to insist on this fact," Binet (1911) cautions, "because later, for the sake of simplicity of statement, we will speak of a child of 8 years having the intelligence of a child of 7 or 9 years; these expressions, if accepted arbitrarily, may give place to illusions." Binet was too good a theoretician to fall into the logical error that John Stuart Mill had identified to believe that whatever received a name must be an entity or being, having an independent existence of its own.

          Binet also had a social motive for his reticence. He greatly feared that his practical device, if reified as an entity, could be perverted and used as an indelible label, rather than as a guide for identifying children who needed help. He worried that schoolmasters with "exaggerated zeal" might use IQ as a convenient excuse: "They seem to reason in the following way: 'Here is an excellent opportunity for getting rid of all the children who trouble us,' and without the true critical spirit, they designate all who are unruly, or disinterested in the schoo. But he feared even more what has since been called the "self-fulfilling prophesy." A rigid label may set a teacher's attitude and eventually divert a child's behavior into a predicted path : 

          Not only did Binet decline to label IQ as inborn intelligence; he also refused to regard it as a general device for ranking all pupils according to mental worth. He devised his scale only for the limited purpose of his commission by the ministry of education: as a practical guide for identifying children whose poor performance indicated a need for special education those who we would today call learning disabled or mildly retarded. Binet wrote : "We are of the opinion that the most valuable use of our scale will not be its application to the normal pupils, but rather to those of inferior grades of intelligence." As to the causes of poor performance, Binet refused to speculate. His tests, in any case, could not decide : 

            Our purpose is to be able to measure the intellectual capacity of a child who is brought to us in order to know whether he is normal or retarded. We should therefore study his condition at the time and that only. We have nothing to do either with his past history or with his future; consequently, we shall neglect his etiology, and we shall make no attempt to distinguish between acquired and congenital idiocy. . . . As to that which concerns his future, we shall exercise the same abstinence; we do not attempt to establish or prepare a prognosis, and we leave unanswered the question of whether this retardation is curable, or even improvable. We shall limit ourselves to ascertaining the truth in regard to his present mental state. 

               But of one thing Binet was sure: whatever the cause of poor performance in school, the aim of his scale was to identify in order to help and improve, not to label in order to limit. Some children might be innately incapable of normal achievement, but all could improve with special help. 

                    The difference between opponents is not, as some caricatures suggest, the belief that a child's performance is all inborn or all a function of environment and learning. I doubt that the most committed antihereditarians have ever denied the existence of innate variation among children. The differences are more a matter of social policy and educational practice. Hereditarians view their measures of intelligence as markers of permanent, inborn limits. Children, so labeled, should be sorted, trained according to their inheritance and channeled into professions appropriate for their biology. Mental testing becomes a theory of limits. Antihereditarians, like Binet, test in order to identify and help. Without denying the evident fact that not all children, whatever their training, will enter the company of Newton and Einstein, they emphasize the power of creative education to increase the achievements of all children, often in extensive and unanticipated ways. Mental testing becomes a theory for enhancing potential through proper education.