Genetics of Childhood Disorders: II. Genetics and Intelligence

Abstract

The modern measurement of human intelligence began in England in the latter half of the ItJrh cenrury when Sir Francis Calton, the half-cousin of Charles Darwin, developed a rest from a simplistic theory, People rake in informarion rhrough rheir senses; therefore, the most inrelligenr people must have the best developed senses. Calton developed a test composed of sensory, motor, and reaction-rime tasks, all of which produced reliable, consistent results. Ulrirnarcly, only Ga1£on's emphasis on the generics of intelligence proved sound; around the rum of the 20rh cenrury, his influential rests were shown to be invalid measures of the complex construct. Binet seized the opening and published the firsr real intelligence test in 1tJ05. Binet's inrelligence rest, based on g'' or general inrelligence theory, comprised many brief tasks of memory, judgmenr, and reasoning. He focused on language, rather than the nonverbal abilities emphasized by Calton: introduced the mental age concepr; and revolurionized resring by insisring that one must be willing to accepr measurement error in order to measure complex human inrelligence. Lewis Terman of Stanford University, also a believer in s- translared, adapted. and standardized the Binet-Simon scales in the United States. When he published the Stanford-Binet in 1916, it became the undisputed king of intelligence rests and retained that ririe t()r nearly a half-century, A second grear influence on the development of IQ tests in the United Stares was America's enrry into World War 1 in 1917. The necessity of resring large numbers of recruirs quickly hi to the development of group-administered intelligence rests: the Army Alpha (a multiple-choice Binet-like test of language abilirics) and the Army Beta (composed of nonverbal tasks), to assess the mental abilities of immigranrs who spoke English poorly. Ultimately, the individually adminisrered Army Performance Scale Examination was developed for suspected malingerers and for others who could nor be rested validly in a group format. The practical ourcomes of rhis war efforr were many, including the notion that IQ rests were useful for adults (nor jusr children), rhey were valid (data from almost 2 million soldiers were analyzed), and they were conrroversial (thanks to irresponsible misinterpretarions of the data hy some prejudiced wartime researchers that led to cries of racism and inferiority). The link between the practical innovations of Binet, Terman, and wartime psychologisrs and current clinical assessment