Detailed History of I.Q.
RANDOM QUOTE: "Scientists animated by the purpose of proving that they are purposeless constitute an interesting subject for study. ? De Officiis" --- Alfred North Whitehead
|There are many individuals who long for the good old days
of simplicity, when we got along with one unanalyzed intelligence.
Simplicity certainly has its appeal. But human nature is exceedingly
complex, and we may as well face that fact. The rapidly moving events of
the world in which we live have forced upon us the need for knowing human
intelligence thoroughly. Humanity's peaceful pursuit of happiness depends
upon our control of nature and of our own behavior; and this, in turn,
depends upon understanding ourselves, including our intellectual
resources. (Guilford, 1969, p. 119)
Although humans have some instinctive behavior patterns, generally individuals are required to learn new behaviors in order to handle changing situations. Until the advent of psychological testing, psychologist accepted the idea that intelligence was the ability to learn, to develop a new way of doing something (Guilford, 1977). This section is organized around the work of individuals involved in the testing movement. An effort has been made to include events in their lives which may have influenced the predisposition each developed toward the task. The testing movement is significant because the tests began to drive theories of intelligence, rather that theories forming the basis for developing tests, a situation Sternberg (1985) maintains the test he is currently developing rectifies.
Individuals Involved in Developing the Test
The exploration of the testing movement begins with Francis Galton, who envisioned a test, continues with James Cattell who provided a name for the test, Alfred Binet who developed a successful test, Charles Spearman who restricted the concept of intelligence, Stern who transferred the test to different audiences, Henry Goddard who translated the test to English, Robert Yerkes who distributed the test to thousands and Lewis Terman who ingrained testing into the American way of life.
The Ground Work
Franz Gall's work in phrenology during the start of the 19th century implanted the concept of a connection between intelligence and physical factors. Gall became interested in the relationship as a young boy when he observed that classmates with prominent eyes tended to have good memories. He carried the idea into his adulthood profession as a physician and scientist and proposed 37 different strengths, weaknesses, and idiosyncrasies an individual might possess which could be revealed through variations in his or her skull size and shape (Gardner, 1985).
Lewis Terman's work a century later may have been influenced by the science Gall and his colleague Joseph Spurzheim developed. As a young boy, Terman encountered phrenology and may have developed his early belief in innate intelligence as a result of it (Fancher, 1985).
Gardner (1985) noted that not all of Gall's ideas were incorrect. Gall was the first modern scientist to believe that different parts of the brain are responsible for different functions. He also claimed "there do not exist general mental powers, such as perception, memory, and attention; but, rather, there exist different forms of...[these] for each of the several intellectual faculties, such as language, music or vision" (Gardner, 1985, p. 13).
Pierre Flourens removed parts of animals' brains and observed their behaviors. Flourens' work cast doubt on Gall's theory of brain specificity after the Frenchman demonstrated that animals could still function without various brain parts. Pierre-Paul Broca questioned Flourens work when he discovered a connection between specific brain lesions and particular physical impairments (Gardner, 1985).
A part of the brain is named Broca. The arguments over the specific functions of the parts of brain reflected the tie developing between physical factors and intelligence. A tie that later came to light with the work of Francis Galton.
Prior to discussing Galton, two additional individuals should be mentioned. Wilhelm Wundt in German and William James in America were instrumental in establishing psychology as a science (Gardner, 1985). In 1875 Wundt established the first psychological laboratory in the world in Leipzig. There he developed the experimental psychological science. His early work focused on functions of the senses. A theme that directed the work of the early investigators. Wundt believed that sensations and feelings combine to become ideas and percepts. The percepts form meanings based on association with past experiences (Zusne, 1975). This theory of associations will surface later in theories of creativity.
About the time that Wundt was establishing his Leipzig laboratory, James established one at Harvard. James was not the experimenter Wundt was, and he did not agree with Wundt on association. James believed that certain inborn capacities of the mind existed and they helped order reality (Zusne, 1975).
The inborn capacities James considered complimented the work of Galton and the beginning of the testing movement.
Sir Francis Galton (1822-1911)
Although the literature emphasizes that Charles Darwin was Galton's older half cousin, and Galton's penance toward the involvement of heredity in intelligence was prompted by the publication of Darwin's Origin of the Species (Clark, 1979; Davis & Rimm, 1989; Howley, Howley, & Pendarvis, 1986), Galton's predisposition toward a heredity controlled intellect was set much earlier. From infancy, Francis Galton was programmed for and expected to be successful. He was the youngest of seven children in a wealthy, prominent English family. Adele, his sickly, older sister of twelve years, took his early education upon herself (Fancher, 1985). The attention she lavished on him encouraged him to excel in scholarly endeavors. By age two and one half, he was able to read simple children's books, and by age four he had mastered some Latin and French. During these early years, his accomplishments were praised and he and his family assumed that he would be among England's finest scholars.
When Galton eventually entered the larger realm of education beyond his home at age eight, he discovered that there were others who could perform academically better than he. During the next ten years he watched his scholastic aspirations for greatness evaporate. Although he did well, he failed to earn the highest honors. This phenomena was inconceivable to him, since he had grown up with all the social advantages. He began searching for an alternative rationale for his limited greatness. The conclusion he eventually drew was that there must be some innate difference between those whose achievement went beyond his and himself. The ground work was set for his later work in intelligence theory and testing.
His father died in 1844 and left him a substantial amount of money. He abandoned an academic career and led the idle life of the wealthy for six years. He eventually decided to explore Africa, an adventure from which he gained notoriety as a geographer and author. He became interested in meteorology, developed the first weather map and discovered high and low pressure weather systems (Fancher, 1985).
Late in 1859, Galton read Darwin's On The Origin of the Species. Influenced by the publication, he concluded that intelligence was related to the keenness of one's senses. The conclusion provided him with a rationale for his earlier academic disappointments. Galton reasoned that evolution would favor individuals with keen senses that enabled them to sense danger more quickly and enabled them to better locate food sources (Davis & Rimm, 1989).
Galton surmised that human talents could also be genetically passed from generation to generation. In Hereditary Genius which he published in 1869 (Carroll, 1982) he presented a list of almost one thousand individuals who represented three hundred different families (Fancher, 1985). He collected data on family performances over several generations in a variety of fields. The most comprehensive study involved eight generations of the Bach family, and he did find that families with a talent such as music tended to produce musicians (Galton, 1952). By today's research standards, Galton's study of families was flawed. He did not possess the knowledge necessary to study the genetic traits of the families; he failed to use random sampling; he failed to take into account environmental conditions, including social influence; and he used secondary sources which were unreliable (Howley, Howley, Pendarvis, 1985).
Because Galton did not believe education was a key factor in intelligence, the only hope he saw for improving society was to develop a genetically superior breed of humans. He went so far as to propose that the state arrange and support a eugenics program which would develop a superior breed (Fancher, 1985). Since individuals usually do not attain eminence until middle age, he needed to find a way to assess an individual's intelligence earlier, while he or she was still at childbearing age. This led to his attempt to measure intelligence.
He set about to measure intelligence through the senses. By 1882 he had established in London the first mental test center in the world (Zusne, 1975). His tests involved visual acuity, auditory acuity, tactile sensitivity, and reaction time (Colangelo & Davis, 1991). Those who wished to be tested paid three pence each for the assessment. As was the case later with Binet, the impetus for part of Galton's work came from low functioning individuals. Galton partly based his sensory acuity tests on observations he had made of mentally handicapped individuals and wrote the following:
The discriminative faculty of idiots is curiously low; they hardly distinguish between heat and cold, and their sense of pain is so obtuse that some of the more idiotic seem hardly to know what it is. In their dull lives, such pain as can be excited in them may literally be accepted with a welcome surprise. (Fancher, 1985, p. 43)
It wasn't until the release of his book Inquiries into Human Faculty and Its Development in 1883 that his work on the creation of a mental test came into the public eye. From 1884 to 1890 he collected data on members of the general public at the Anthropometric Laboratory (Carroll, 1982), and although he collected data on more than nine thousand paying customers, he had no way of precisely measuring interrelationships. An advancement which eventually did materialize as a result of this work was the Pearson Correlation. Because of a need to analyze the data from his study, Galton paved the groundwork for the correlation statistical measure, which was eventually developed by his student Karl Pearson. Galton can also be credited with founding the study of measurement of individuals, a field which was further developed by J. M. Cattell. Galton was the first to make extensive use of the questionnaire method for gathering data in psychology. He also formulated the concept of regression toward the mean. He was one of the first to delve into twins studies (Fancher, 1985). Galton can also be called the inventor of the percentile rank (Carroll, 1982).
Although Galton's legacy is the nature side of the nature-nurture controversy, he did not totally rule out the influence of the environment. Tannenbaum (1983) noted that Galton recognized genius as a "matter of reputation for greatness, judged by contemporaries or by posterity, not as something revealed through psychometrics" (p. 67). Tannenbaum went on to report that many of the personality traits of geniuses described by Galton have been confirmed by more than a century of research:
Nevertheless, his insights into persons who had earned renown in science...led him to the conclusion that these people were endowed with superior intellectual ability, tremendous energy, good physical health, a sense of independence and purposefulness, and exceptional dedication to their field of productivity . . . they had vivid imaginations, strong, quick, and fluent mental associations, and a drive powerful enough to overcome many internal or external constraints. (p. 67)
James McKeen Cattell (1860-1944)
Cattell conducted doctoral studies in reaction time with Wilhelm Wundt in Leipzig. He collected thousands of measurement on himself and another student. While Cattell was interested in individual differences in reaction time, his professor was interested in general features of the mind (Zusne, 1975). Eventually Cattell completed his degree in Leipzig and moved to England where he met Francis Galton. For a brief time Cattell set up a laboratory at Cambridge similar to Galton's and began pursuing his interest in individual differences. He returned to the United States and served as a professor of psychology at the University of Pennsylvania for a limited time (Carroll, 1982) before becoming a prominent figure in 1888 in the new psychology of individual differences at Columbia (Fancher, 1985).
The term "mental tests" was penned by Cattell in an 1890 article titled, "Mental Tests and Measurement" which was published in Mind (Zusne, 1975). In the article he proposed ten mental tests to be used with the general public. These tests were part of a series of 50 which were being completed by graduate students. Cattell attributed much of foundation for this work to Galton. The ten tests involved dynamometer pressure, the strength of one's hand squeeze; rate of movement of the hand through a distance of 50 centimeters, when started from rest; sensation areas, the so-called "two-point threshold;" pressure causing pain; weight differentiation; reaction time for sound; time for naming colors; bisection of a 50-centimeter line; judgment of ten seconds of time; and number of letters repeated in one learning (Fancher, 1985). Tannenbaum (1983) noted that of the ten tests, four dealt with temporal functions and the rest with sensory acuity or simple motor skills. According to Davis and Rimm (1989), Cattell's call in 1890 for tests which would measure mental ability was partly responsible for the favorable reception Binet's test later received in the United States.
A number of investigators enthusiastically began embracing mental testing in the 1890's, although nonproductive results began to dampen the movement. By this time Karl Pearson had perfected his correlation technique. In 1901 one of Cattell's graduate students, Clark Wissler, compared the mental test scores of 300 Columbia University and Bernard College students with their academic grades using Pearson's formula and found little correlation. Wissler's results disappointed psychologists (Fancher, 1985). This was the first "substantial" application of the formula (Carroll, 1982. Wissler eventually left psychology and became an anthropologist (Fancher, 1985) while Cattell's "anthropometric test movement" died as psychologists began following the work of Alfred Binet, who was developing measures of "high mental processes" (Zusne, 1975). Despite his failed attempt at developing a "mental test," Cattell provided a number of contributions. He founded The Psychological Corporation in 1921, which is still in existence (Zusne, 1975). He produced a large-scale study of over 1000 eminent American men of science which revealed the impact on social class on professional careers in science (Tannenbaum, 1983). As Zusne (1975) noted:
Cattell never wrote a text and was author of relatively few papers. His influence on psychology was very strong, nevertheless, mainly because of his personality and because he happened to represent the functionalist point of view in the form of mental tests when Americans were most ready to accept both. His ability and willingness to speak out fearlessly on issues, psychological and social, and to be involved in public affairs made him prominent. (p. 226)
Alfred Binet (1857-1911)
Binet entered the field of psychology somewhat through the back door. He left medical school after he suffered an emotional breakdown. While browsing through books on psychology at the library during his recovery, he became interested in psychological experiments. Following a premature article touting his own theory of the famous two-point threshold experiments, which was severely rebuked by the Belgian physiologist Joseph Delboeuf, Binet became a fan of the work of John Stuart Mills, an associationism psychologist.
In an 1883 article entitled "Le Raisonnement dans les Perceptions," (Reasoning in Perception) published in Revue Philosophique Binet wrote:
The operations of the intelligence are nothing but diverse forms of the laws of association: all psychological phenomena revert to these forms, be they apparently simple, or recognized as complex. Explanation in psychology, in the most scientific form, consists in showing that each mental fact is only a particular case of these general laws. (Fancher, 1985, p. 52)
Binet eventually recognized the limitations of the theory, but it would remain an influence on this thinking and later surfaced when he set about developing an intelligence test. "Binet would argue that 'intelligence' whatever else it was could never be isolated from the actual experiences, circumstances, and personal associations of the individual in question" (Fancher, 1985, p. 53).
Binet began working with Charles Fere' under the direction of Jean Martin Charcot on the relationship between hysteria and hypnosis. Charcot believed the in-depth study of a few subjects was preferable to working with a large sample of subjects. The case study approach left an impression on Binet. The experiments in hysteria and hypnosis that Binet and Fere' conducted with a subject named Blanche Wittmann were tainted with poor design and were eventually discredited because the two had failed to recognize the subject's sensitivity to unintentional suggestion. Despite public humiliation, Binet had learned case-study method well from Charcot while at the Salpetriere Hospital. He also managed to produce three books and 20 articles on topics as esoteric as sexual fetishism, illusions of movement, and child psychology (Fancher, 1985).
In the autumn of 1891, he approached Henri Beaunis who had founded the newly created Laboratory of Physiological Psychology at the Sorbonne, and offered to work without pay (Zusne, 1975). Binet had learned his lesson regarding acceptance of unauthenticated authority and became a model experimenter who went on to thoroughly test his theories. Three years later he became the director of the laboratory. During his life time he never was paid for the position.
About the time he was ending his work at Salpetriere, he began experimenting with tests and puzzles on his young daughters Madeline and Alice and published three articles in 1890. He noted that the difference in reaction time of children compared to adults was contingent on whether the child was paying attention. The importance of the child's state of mind and the influence of the environment on testing would remain significant to Binet (Fancher, 1985).
He reported empirical data on his daughters as they grew and included a discussion of the different styles of intelligence between them in a 1902 publication entitled L'Etude Experimentale de l'Intelligence (The Experimental Study of Intelligence) (Zusne, 1975). He noted his daughters' different styles when they were learning to walk and equated the difference to two equally intelligent adults using different ways to solve a problem:
Mere numbers cannot bring out . . . the intimate essence of the experiment. This conviction comes naturally when one watches a subject at work . . . The experimenter judges what may be going on in [the subject's] mind, and certainly feels difficulty in expressing all the oscillations of a thought in a simple, brutal number, which can have only a deceptive precision . . . We feel it necessary to insist that the suggestibility of a person cannot be expressed entirely in a number. (Fancher, 1985, pp. 62-63)
Although he appreciated the richness of the case study, Binet saw the need to develop some standard dimension along which individuals could be compared quickly. Although he and his assistant Victor Henri only had a vague idea in 1896 about what they wanted to study in this new field which Binet called individual psychology, they knew they had to begin testing the more intellectual and complicated processes. His observations on the "functional" nature of young children's thought when they described objects prompted him to conclude that abstraction was one of the "hallmarks" of increasing intelligence. The fact that a child often did as well as an adult on many sensory tests compelled him to abandon those tests. He and Henri began testing memory, imagery, imagination, attention, comprehension, suggestibility, aesthetic sentiment, moral sentiment, muscular strength and willpower, and motor ability and hand-eye coordination. After eight years of study, they reported no success in 1904:
...it is premature to look for tests permitting a diagnosis during a very limited time (one or two hours), and that, much to the contrary it is necessary to study individual psychology without limiting the time especially by studying outstanding personalities. (Fancher, 1985, p. 68)
Because of the influence of a young physician named Theodore Simon who in 1899 wanted to do doctoral research with Binet, Binet became interest in the mentally handicapped. At the same time he became a member of La Societe Libre pour l'Etude Psychologique de l'Enfant (Free Society for the Psychological Study of the Child). As a result of the university education laws, French law required all children be given several years of public education. This included mentally handicapped children (Fancher, 1985).
In the fall of 1904, the Minister of Public Instruction of France appointed a committee to study and make recommendation regarding the education of mentally retarded children in Paris (Zusne, 1975). Binet was appointed to the group because of his position in La Societe, and he and Simon were hired for the task of developing an assessment method. Officials had noticed that
...teachers' judgments of student ability were biased by such traits as docility, neatness, and social skills. Some children were placed in schools for the retarded because they were too quiet, too aggressive, or had problems with speech, hearing, or vision. (Davis & Rimm, 1989, p. 5)
He immediately saw a need for a diagnostic system (Fancher, 1985) and it was Binet and Simon who opened the flood gates to test the special mental qualities of children (Tannenbaum, 1983).
The French government had established three levels of mental retardation and Binet and Simon set out in 1904 to develop a test designed to distinguish the three levels, as well as a level of normal weakness. They wanted the tests to be free of school related activities. They soon discovered that different levels of mastery were associated with a child's age. Their first intelligence test was published in 1905 and consisted of 30 items in ascending difficulty. The easiest item involved following a match with one's eyes which they believed reflected the earliest sign of intelligence. The task was also considered the upper limits of the most retarded. The most difficult tasks were beyond the ability of the subnormals, as they were called at the time, but could easily be passed by a child of 11 or 12 years. The test contained items to discriminate over a range of mental functions, including attention, memory, discrimination, imagination, and verbal fluency. Its limited field testing was conducted with 50 normals and 45 subnormals (Fancher, 1985).
Binet believed intelligence was a multifaceted psychological faculties which were tied together in a real world and controlled by practical judgment.
There is in intelligence, it seems to us, a fundamental agency the lack or alteration of which has the greatest importance for practical life; that is judgment, otherwise known as good sense, practical sense, initiative, or the faculty of adapting oneself...Compared to judgment the rest of the psychology of the intellect seems of little importance. (Fancher, 1985, p. 74)
His test was expanded to 58 items in 1908 and included ages 3-13. The new test concentrated greater emphasis on separation at the six, seven and eight-year-old range. In 1911, Binet made his final revision of the test and refined it to include five items at each age level. He also extended the scope to include 15-year-olds and added an adult category (Fancher, 1985).
It was in the scoring of this final revision that the concept of mental age was born (Colangelo & Davis, 1991; Davis & Rimm, 1989; Lyman, 1986; Zusne, 1975), although Binet actually used the term level (Fancher, 1985). A subject received one-fifth of a year for each correctly answered question on the test which determined his or her level. Binet believed that children grow in intelligence and are therefore at different stages at different ages. Even though he develop a scoring system which provided a specific level, throughout his life Binet maintained that a single number could not be used to describe an individual's intelligence. He believed this could only be accomplished through a case study (Fancher, 1985), an approach which Reis and Renzulli (1985) three-quarters of a century later advocate for identifying children for gifted program services.
Binet always maintained that the test was intended only for healthy, motivated subjects who were from ordinary French culture. Binet believed that intelligence was not static and was subject to substantial change in an individual. His 1909 publication Idees Modernes sur les Enfants (Modern Ideas about Children) presented ideas for improving a child's intelligence, even at the lowest levels where he felt attention could be expanded. He believed individuals did have a mental ceiling, but few people ever approached that limit. Clark noted (1979) that Binet's belief that intelligence was educable would not again be sounded until the 1960s and that many of his article and speeches could be considered radical even today.
In 1905, Binet felt it might be possible to further extend his scales to the normal adult and even to the genius, but in 1908 he expressed reservations and wrote, "We are of the opinion that the most valuable applications of our scale will not be for the normal subject, but instead for the inferior degrees of intelligence" (Fancher, 1985, p. 81). Interestingly, he later reversed his position again and extend the scales for adults. The foundation of Binet's test was developed through his work with children, whose learning patterns do not always replicate adults. If Binet had initially started with adults when developing a test, the test and theories of intelligence might be viewed very differently today.
Binet's theory about intelligence did not actually match the test he developed, a grand tradition that some psychometricians continue even today.
What we call intelligence, in the narrow sense of the term, consists of two chief processes: First, to perceive the external world, and then to reinstate the perceptions in memory, to rework them, and to think about them. (Binet, 1890 as cited in Carroll, 1982, p. 36)
In 1909 Binet and Simon listed the following three criteria for intelligent thought: la direction, the taking and maintaining of a given mental set; l'adaptation, the adaptation of thought for the purpose of obtaining a given end; and la critique, the taking of a critical attitude toward one's thought, and correcting it where necessary (Carroll, 1982).
Galton and Binet both died in the same year. Galton was an old man and had long ceased working; Binet was 54 and at the height of his career. Despite the 277 publications credited to him (Dennis, 1954 cited in Albert, 1983), Binet did not leave behind many followers and his techniques were soon applied with "Galtonian" ways (Fancher, 1985).
Charles Spearman (1863-1945)
Spearman came to the field of psychology via a military career. The combination of a hidden philosophical side and a logical-mathematic fashion with which he was probably trained in the military was probably influential in his formulation of a theory of intelligence. When he was 34 he abandoned his military career to pursue psychology. He went to Germany and studied at the University of Leipzig with Wilhelm Wundt. Wundt's "voluntaristic psychology," which postulated that intentions and motives played a role beyond associationism, and ideas can be combined and related in new and hitherto unseen or heard ways when full conscious attention is focused on them, was very much to his liking. He had taken offense at John Stuart Mill's theory of associationism, which he had read while still in the military.
During the seven years he took to complete his Ph.D., Spearman began conducting experiments based on the work of Galton. Spearman designed a correlation matrix using test scores and academic rank using boys from a school in Hampshire, England (Carroll, 1982). Without knowing it he repeated the early work of Cattell which had been discredited with Wissler's use of the Pearson correlation. His own work showed a higher correlation and he wrote:
Had I seen [Wissler's] work earlier, I should certainly have thought the matter disposed of and should never have started my own work in this direction. Since the conflicting results were there, however, they had at least to be explained. After much pondering over them, I had at last a happy thought which embodied itself in the concept of "attenuation." (Fancher, 1985, p. 88)
What Spearman realized was that any measure of a variable will have some inaccuracy. The correlation of two measures will be underestimated because of the error variability of the measures. He set about developing a correlation formula which would compensate for the error involved in measurement. Spearman began correlating and adjusting a variety of scores with his new formula. The results produced correlations slightly above +1.00, he attributed the excess over 1.00 to random error. The mathematical procedure he developed became known as the tetrad equation. Factor analysis was not available at the time, since it was not developed until the 1930's (Zusne, 1975).
Spearman correlated a variety of subject grades and music skills for a group of boys from an upper-class preparatory school. He reasoned that the correlation among all the scores represented some general ability. He noticed that some of the scores correlated more highly than others. He attributed these correlation differences to specific abilities which the various variables assessed (Fancher, 1985).
In 1904, he first published his two-factor theory of intelligence in The American Journal of Psychology in an article titled " 'General Intelligence,' Objectively Determined and Measured." The paper was widely discussed and in 1906 he was offered a position at University College London where he spent the rest of his career.
Spearman began applying his statistical technique to scores on the Binet tests. He was impressed with the tests, but not with Binet's theory that intelligence was a collection of diverse functions grouped in different and individualized patterns for different people. Spearman felt his general factor was literally brain power, "the general level of mental energy which led people to perform well or poorly on all sorts of intellectual acts, but particularly those requiring abstract thinking" (Fancher, 1985, p. 95). He lent his support to his mentor Francis Galton's Eugenics Society and wrote in 1912, "One can...conceive the establishment of a minimum index [of g] to qualify for parliamentary vote, and above all, for the right to have offspring" (Hart & Spearman, 1912 as cited in Fancher, 1985, p. 95)
He refined his two factor theory of intelligence in 1927, noting that any mental test contained two types of information, the information which was specific to the test and the information representing a general factor. The first was now commonly referred to as "s" and the later "g". The "g" factor was what Spearman and later Wechsler felt was the best representative of the intelligence trait (Howley, Howley, & Pendarvis (1986). Spearman summarized his work in a book entitled The Abilities of Man, in which he also related the "g" and "s" factors to "attention, conation, and similar psychological processes" (Zusne, 1975, p. 244). In that publication he attributed the general factor to be the power of reasoning (Carroll, 1982).
The British statistician Godfrey Thomson touched off a debate that continues to-date when he demonstrated in the 1920's that even scores randomly created with tosses of dice could produce a hierarchical pattern of correlation coefficients similar to those Spearman utilized (Fancher, 1985).
By the 1930s Spearman had realized that other group factors beyond "g" existed. Along with Karl Holzinger, Spearman and his associate started the "Unitary Trait Study" to look into what kinds of group factors could be established (Carroll, 1982).
Gardner (1983) noted that debate in intelligence testing today still ranges between those who follow Spearman and his general factor of intelligence and those who follow Thurstone and his family of discrete mental abilities. Both sides can use statistical analysis to support their side. Gardner reported that the support for "g" comes primarily because most intelligence tests are paper and pencil and test the linguistic and logical-mathematic abilities which schools value, which is why "g" can somewhat accurately predict school success. Tannenbaum (1991) includes the "g" factor in his model as one five factors which interweave to form giftedness and wrote that "separate cross-validation studies of three batteries of widely used aptitute [sic] tests showed that a single general ability factor usually predicted criterion performance in each of a number of educational subjects and in job requirements at least as well as did the best single aptitude subtest in the respective batteries" (p. 27).
Despite giving Galtonians the one dimensional, inherited general ability they sought and propelling interpretation of intelligence away from Binet's pluralists view, Spearman left a well-known statistical legacy with the Spearman rank order correlation coefficient, the Spearman-Brown prophecy formula, and the correction for attenuation of the correlation coefficient (Zusne, 1975).
William Stern (1871-1938)
The German psychologist William Stern developed the idea of the intelligence quotient in 1912. While studying student scores on Binet's test he noticed that the variations in mental age increase proportionally with the mental age. A students who at age nine might score one year below age would score two years below age level when he reached age 13. Stern discovered that if the chronological age were divided by the mental age, the ratio was somewhat constant (Carroll, 1982). He named the ratio of the mental age divided by the chronological age the intelligence quotient (Fancher, 1985). Earlier, Stern had translated Binet's French niveau intellecuel (intellectual level) into German Intelligenzalter (intellectual age). Fancher (1985) noted that the term age implies more precision and carries a connotation of innate sequences more than Binet's term level. Although Stern is primarily known for developing the intelligence quotient, his theory of intelligence is worth mentioning. He agreed with Spearman that "intelligence does really signify a general capacity which colors in a definite way the mental behavior of an individual" (Fancher, 1985, p. 101), however he cautioned the following:
There are persons who have a pretty high grade of general intelligence, but who manifest it much better in critical than in synthetic work; again, there are persons in whom the receptive activities of the intelligence are superior to the more spontaneous activities, and so on. (Stern, 1914, cited in Fancher, 1985, p. 101)
Stern was a versatile person who produced a three-volume set, Person und Sache: System der philosophischen Weltanschauung in which he advocated the study of the total person. He believed that "...[e]very mental function is centered in a person, which is therefore the object of psychological study rather than the function" (Zusne, 1975). At this point in the review of the testing movement, the underlying concept for most of the current mental ability tests had been established and a standardized score was set. One can observe that the test is already being applied with incompatible theories of intelligence. A second point worthy of noting is a "Catch 22" in which the individuals responsible for refining the results of the test are cautioning against the limiting refinement of what intelligence is.
Henry Goddard (1866-1957)
Goddard was a high school teacher and principal before he began his studies for a Ph.D. in psychology at age 30. He studied under G. Stanley Hall, who was the first president of the American Psychological Association and founder of the American Journal of Psychology. Goddard's thesis was on psychological factors in faith healing.
After a brief stint teaching at Pennsylvania's West Chester State Teacher's College, he was named director of research at the Training School for the Feebleminded in Vineland, New Jersey. Goddard visited Europe and attempted to meet Binet. He was not successful and was disappointed in Binet's work (Fancher, 1985) . Upon returning to the United States he created his own version of Binet's test ( Zusne, 1975) and to his surprise found that it worked well when classifying the children at Vineland. In 1911, he reported on the evaluation of 2000 normal children (Stanley, 1976) and as Colangelo and Davis (1991) noted, "The transition from using the Binet tests with below-average children to employing them with normal and above-average children thus was complete and successful" (p. 6).
Goddard was not a fan of Binet's theory of intelligence. The Mendelian theory of dominate and recessive genes had impressed him and he applied it to intelligence. As Fancher (1985) noted, Goddard's conception of intelligence was more unitary than Spearman and more exclusively hereditary than Galton. While Galton was an advocate of fostering population growth at the upper end of intelligence distribution, Goddard was dedicated to prevention at the lower end. He believed individuals at the lower end should not be permitted to reproduce and in 1912 wrote a book entitled The Kallikak Family: A Study in the Heredity of Feeble-mindedness. With the aid of his assistance Elizabeth Kite, he followed two separate lines of offspring of a Revolutionary War era gentleman. The one line was purported to be mentally feeble, while the other healthy. The book contained family photos which Goddard had retouched and exaggerated accounts of the family history.
Goddard wanted to limit reproduction by "feebleminded" people, but he felt the public would not accept mass sterilization of this group, so instead, he proposed building institutions to house the bulk of them. At these institutions they would be prevented from conceiving children. Although his plan was expensive, Goddard argued that the long term benefits would outnumber the short term expense, since feeblemindedness would be eliminated in one generation and no longer be a financial burden.
He soon turned his attention from the feebleminded and began administering the test to immigrants arriving at Ellis Island. A large percentage of the immigrants did not do well on the test and although Goddard did acknowledge that poor environments and a lack of knowledge of American culture might have influenced their scores, he cautioned that eastern Europeans might be unwanted denigrated stock.
Goddard has the dubious honor of probably being the first individual to be guilty of massive abuse of the tests. It was he who opened the flood gates for execution of intelligence tests for social uses. His primary contribution was bringing the Binet-type test to the attention of American psychologists. He did modify his theory of hereditary feeblemindedness and acknowledged that it had been overstated and that proper education could improve the performance of many children. He left Vineland in 1918 and went to Ohio State University where he became interested in gifted children (Fancher, 1985).
Robert Yerkes (1876-1956)
Yerkes was president of the American Psychological Association when the United States entered World War I in 1917. He was anxious to show the value of the young field of psychology (Fancher, 1985). Yerkes proposed blanket administration of intelligence tests to military recruits. He stated, "We should not work primarily for the exclusion of intellectual defectives, but rather for the classification of men in order that they may be properly placed in the military service" (Fancher, 1985, p. 119).
Yerkes' proposition changed the role of mental testing in two ways. It expanded the use of the test and implemented group, rather than individual administration. Secondly, it changed the role of the test. The scores were now being used for positive as well as negative selection. Instead of indicating what an individual could not accomplish, it was being used to predict what one might accomplish.
Yerkes convinced the Surgeon General of the army to consider his plan; the navy had turned him down. His committee began developing the Army Alpha test which was based on the previous work of Goddard, Otis, Bingham, Wells, and Thurstone. Lewis Terman and David Wechsler, among others, helped develop the test (Fancher, 1985). For those developing the test, "...the critical points were abilities to understand language to perform reasoning with semantic and quantitative relationships, to make 'practical judgments,' to infer rules and regularities from data, and to recall general information" (Carroll, 1982, p. 36).
Their test took 25 minutes to administer and consisted of eight subtests. Because such a high number of recruits were illiterate in English, a second test, called the Beta, was developed for illiterate recruits. Both tests produced a mental age score, the concept of IQ which had been proposed earlier by Stern was considered inappropriate for these tests (Carroll, 1982).
A trial was conducted with the test on 80,000 men. The army was sufficiently impressed and authorized testing for all new recruits beginning in 1918. The tests were administered at a rate of 200,000 per month, and over 1,750,000 had been administered by the end of the war in November of 1918 (Fancher, 1985).
With the development of group tests, Carroll (1982) noted the occurrence of three breaks from Binet's original thinking. First, with Binet's individual test, the respondent was expected to produce a correct answer, as opposed to recognize one, which existed with a group test. Second, the Binet test was scored by how far one could advance through a set of task which were theoretically arranged from simplest to most complex. The group test assessed how many items one could correctly answer at restricted time frame. Finally, the group test had a heavy emphasis on paper and pencil skills.
Following the group testing in World War I, a flood of tests which imitated the army tests were initiated. Some were poorly designed with no regard to test construction, while others were developed by some of the leading psychologists of the time, including Otis, E. L. Thorndike and Thurstone (Carroll, 1982). Tannenbaum (1983) noted that fervor to develop tests of mental measurement was so great in the early 1900s that no less than 350 titles of intelligence, achievement, aptitude and personality tests were available. Carroll (1982) noted that Edward Thorndike (1874-1949) was the person most instrumental in the United States in disseminating the new discoveries in correlational methods. Thorndike's book, Introduction to the Theory of Mental and Social Measurements (1904), contained detailed discussions of statistical methods, including correlation, appropriate for the construction and application of mental tests. Thorndike saw intelligence as a general capacity that manifests itself in a large variety of tasks. It was the capacity to form connections among ideas and concepts. Persons of high intelligence were those who had the capacity to form a large number of connections and had the opportunity through experience and education to do so.
Yerkes had grown up on a Pennsylvania farm. He was headed for a medical career when he detoured to Harvard and became interested in animal behavior, and eventually psychology. Like many of the individuals describe in the mental measurement movement, he was also an advocate of the eugenics movement.
Yerkes disagreed with some of the format of Binet's test. Binet had designed certain types of tests for certain ages. Yerkes believed all subjects could be better compared it they had attempted the same types of tasks. For example, Binet may have only had ten-year-olds tested for memory of a span of digits. Yerkes felt that items should be included at each level and he was influential in having his idea used with the army tests.
The social controversy involving Yerkes work started after the end of the war. The army testing program provided a massive amount of data which Yerkes and his colleague began to analyze. Fancher (1985) pointed out three controversial finding which Yerkes revealed. First, Yerkes asserted that the average army recruit had low native intelligence. In his 800 page book entitled Psychological Examining in the United States Army published in 1921, he calculated the average recruits mental age to be around 13. Second, A Study of American Intelligence was published in 1923 by Yerkes' colleague Carl Brigham. He reported that immigrants from northern Europe scored lower than native-born American whites, and also that immigrants from southern and eastern Europe scored much lower than those from northern Europe. Brigham failed to consider that the amount of time an immigrant had been in the country influenced his test score and northern Europeans, on the average, had been in the country much longer than the other two groups. Third, Yerkes and Brigham noted that blacks scored lower than whites and blacks from northern states often scored higher than whites from southern states.
Yerkes failed to consider the environmental factors of the subjects, as well as the inappropriateness of the test. The statistical report of the army testing program contained one of the early applications of multiple correlation in psychological testing (Carroll, 1982).
Yerkes was best known in psychology circles not for his work in human intelligence, but for experimental studies of animal behavior, an area he pioneered with Thorndike. He is best known for the Yerkes-Dodson law which states that "strong motivation interferes with learning a difficult discrimination problem but helps to learn a simple one" (Zusne, 1975, p. 325).
Lewis Terman (1877-1956)
Terman was involved in the development of the army tests. He too grew up on a farm, only in Indiana. Terman was academically advanced and moved directly to third grade after a single term in first grade. He had exhausted local education opportunities by the time he was 12. He entered teacher's' college when he was 15. Eventually Terman ended up at Clark University studying with the G. Stanley Hall (Fancher, 1985). Hall believed in predeterminism which assumes that an individual is "programmed in a sequentially time-controlled way, and that regardless of events or environments the program will prevail" (Clark, 1979, p. 16). Goddard had just finished his fellowship with Hall when Terman entered.
Terman developed an interest in precocious children and mental testing while at Clark. Hall disagreed with Cattell and distrusted mathematical methods, so he did not encourage Terman's interest in mental testing. However, Terman did compare high performing students with low performing students for his Ph.D. theses. At the time he was unaware of the work of Binet and Simon, and he developed an eight part test consisting of invention and creative imagination, logical processes, mathematical ability, language mastery, interpretation of fables, the game of chess, memory, and motor skill. He did not find significant differences, partly because of the test and partly because he had failed to take into account the subject's age.
When Terman became familiar with the Binet test he was impressed primarily because it addressed some of the testing problems he had encountered with his theses. Terman and his graduate student H.G. Childs noticed that scores on the Binet test were inflated for young American children and deflated for older students. They set out creating a more accurate test for American students and introduced this version in a 1912 article. The second revision in 1916 was called the Stanford Revision of the Binet-Simon Scale, and it was field tested on 2300 individuals. This later became know as the Stanford-Binet which has been the standard against which all subsequent tests have been measured (Fancher, 1985). One of Terman's modifications was the application of Stern's mental quotient to measure intelligence. Terman referred to it as intelligence quotient or IQ (Zusne, 1875). Terman had been one of the first people to be tapped by Yerkes in 1917 to develop the army tests, and he went on to develop a variety of tests and became a wealthy man from the royalties (Fancher, 1985). He published the first revision of the Stanford-Binet in 1937 with Maude Merrill (Zusne, 1975). It was again revised in 1960 and 1986 (Davis & Rimm, 1989).
Carroll (1982) noted that "probably the person most responsible for the dissemination of psychological measurement statistics in the 1920's was Truman L. Kelly...[whose] book Statistical Method marked an important milestone in the application of rigorous statistical methodology to problems in psychology, education, social science fields" (p. 46). Kelly worked with Terman from 1920-31 at Stanford University in the development of the Stanford-Binet other tests (Carroll, 1982).
Terman was of the Galtonian school and believed that intelligence was genetic. Clark (1979) noted that the Stanford-Binet "originated when no one questioned the belief in fixed intelligence. Later revisions are still based on this assumption" (p. 15). Terman also felt that intelligence was the ability to do abstract thinking. Guilford (1977) emphasized that Terman failed to define abstract thinking and the Stanford-Binet test which Terman developed called for understanding or knowledge and memory more than abstract thinking. Tannenbaum (1991) noted that Terman never proposed a theory of intelligence; he simply developed a test to assess abstract thinking ability.
In 1940, psychologists at the University of Iowa reported studies which showed that IQ scores increased for students adopted into good foster homes. The researcher attributed the increase to the environmental factors. Terman led the charge against the report and claimed that the researchers had used poor methodologically and had overstated the environmental differences. He was apparently sensitive to the environmental, a stance he would soon modify.
He began a longitudinal study in 1920 of 1528 boys and girls with IQ scores of 140 and above (Colangelo & Davis, 1991; Davis & Rimm, 1989; Howley, Howley, & Pendarvis, 1986). His earlier position on genetics was modified some in the fifth volume of his Genetic Studies of Genius series (Terman & Oden, 1947) when he wrote:
At any rate, we have seen that intellect and achievement are far from perfectly correlated. Why this is so, what circumstances affect the fruition of human talent, are questions of such transcendent importance that they should be investigated by every method that promises the slightest reduction of our present ignorance. So little do we know about our available supply of potential genius, the environmental factors that favor or hinder its expression, the emotional compulsions that give it dynamic quality, or the personality distortions that make it dangerous. (p. 352)
Several legacies were left by Terman from the study. One was that the gifted differ from the nongifted in degree rather than in kind (Tannenbaum, 1991). A second was that by the 1930s the terms giftedness and high IQ were becoming synonymous (Ramos-Ford & Gardner, 1991)
David Wechsler (1896-1981)
Wechsler immigrated to the United States with his parents when he was six years old. He was studying memory loss associated with long term alcoholism for a master's degree when the United States entered World War I. He joined the Yerkes testing program while he was in the army. Wechsler administered individual Stanford-Binet tests to recruits who had done poorly on the alpha or beta tests. During this time he recognized that the test questions were not appropriately assessing soldiers' abilities (Fancher, 1985).
Based on observation he made with children's scores, Wechser came to the conclusion that intelligence was not entirely fixed. He noted that as children grew older, the variance in their scores diminished. He suspected this might be do to environmental factors. A second area where he broke with traditional theorists was regarding the "g" factor of intelligence. Wechsler had briefly studied with Spearman and felt Spearman theory was too restrictive and overlooked the factors of motivation and personality. He noted that individuals might excel at certain types of items on a test. In 1932, he published a paper in the Journal of Applied Psychology entitled "Analytic Use of the Army Alpha Examination" in which he touted the advantages of the army tests over the Standford-Binet in certain cases because they allowed for the diagnosis of special abilities and disabilities (Fancher, 1985).
That same year he was appointed head of psychology at New York's Bellevue Hospital. Since he was responsible for testing thousands of adults, he set about to develop an appropriate test which first, was designed for adults rather than children and second, which viewed intelligence as multidimensional. Since adult performance on tests tended to level off in the twenties, he needed to abandon the Stern-Terman formula which divided mental age by chronological age. Wechsler based his scoring of the distribution of the normal curve. He equated the mean score for an appropriate age group to a value of 100 and developed tests which resulted with a standard deviation of 15. The first Wechsler Bellevue Scale was developed in 1939 and revised as the Wechsler Adult Intelligence Scale (WAIS) in 1955.
The tests consisted of eleven subtests, each of which provided a score. Six of the subtest covered verbal material, much as the army Alpha test did, and five of subtests covered performance material, similar to the army Beta test. Information, comprehension, arithmetic, digit span, similarities, and vocabulary skills were included in the verbal section. Picture arrangement, picture completion, block design, object assembly and digit symbol substitution entailed the performance section. As Fancher (1985) noted, "In the hands of skillful interpreters, the Wechsler test patterns provide multiperspectived views of the intellectual workings of many different kinds of people" (p. 156). A children's scale was developed in 1949 and a preschool and primary scale was developed in 1963. With Wechsler, we return to Binet and the roots of the testing movement. Wechsler's work followed the philosophy and spirit of Binet. Wechsler (1969) wrote in 1950 that "general intelligence cannot be equated with intellectual ability, but must be regarded as a manifestation of the personality as a whole...factors other than intellectual enter into our concept of general intelligence, and...in everyday practice, we make use of them knowingly or not" (p. 73). Wechsler noted that some of these factors are drive, persistence, will, and preservation, "or in some instances, to aspects of temperament that pertain to interests and achievement" (p. 69).
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