Thorndike, Edward L. (1874–1949)
THORNDIKE, EDWARD L. (1874–1949)
Edward L. Thorndike was an American psychologist, educator, lexicographer, and pioneer in educational research. The groundwork for research into learning was provided in 1913–1914 by his three-volume Educational Psychology, which set forth precepts based on his experimental and statistical investigations. These precepts–which covered such wide-ranging topics as teaching practices and individual differences between students and such administrative concerns as promotion decisions and grouping according to ability–came to dominate professional thinking.
While such men as John Dewey and Robert M. Hutchins influenced the philosophy of education, Thorndike and those whom he inspired wrote reading and arithmetic books for pupils, school dictionaries and spelling lists, tests, and pedagogical guidebooks and teachers' manuals. Because, however, it is far more difficult to assess influence in the operations of many thousands of American classrooms than to analyze ideas in the words of educational theorists, Thorndike's contributions are taken largely for granted.
The Man and His Career
In its external details, Thorndike's life was uneventful and circumspect; its drama lay in his genius (his IQ was estimated at nearly 200) and in the tumultuous times to which his work bore such marked reference. Born in Williamsburg, Massachusetts, on August 31, 1874, of a family line resident in New England since 1630, Thorndike, like a surprising number of other notables of his day, was reared in a clergyman's household. But in an era when science was challenging religion as a source of truth, when inquiry and universal education threatened dogmatism and sectarian inculcation, and when a career in the church was becoming less attractive than life in the laboratory, Thorndike rejected even his father's liberal brand of Methodism for an agnostic secularism. Yet, in his evangelical regard for science, Thorndike transferred to science a religious-like belief in the possibility of personal and societal salvation. Science was, he said repeatedly, "the only sure foundation for social progress."
Thorndike grew up in a household where excellence was expected, for the children of a minister were to be models for the congregation in all matters. In academic performance the Reverend Thorndike's children complied, all earning excellent grades and winning the scholarships which made college studies possible. In addition, all established academic careers: Ashley as a professor of English, Lynn as a historian, and Mildred as a high school English teacher; eventually all three Thorndike brothers taught at Columbia University. Edward Thorndike's children continued this scholastic brilliance but turned, like father, from literary to scientific and mathematical careers. All four children earned Ph.D. degrees: Elizabeth Frances in mathematics, Edward Moulton and Alan in physics, and Robert Ladd in psychology. Thus, from his own boyhood, when his parents encouraged early reading and supervised homework, to his own close guidance of his children's schooling, Thorndike brought high degree of personal involvement to his professional study of education.
Because of the church's requirement that a minister be moved regularly, Thorndike grew in eight New England towns before 1891, when he left home to enter Wesleyan University in Middletown, Connecticut. Never feeling at home anywhere in his childhood, when he possessed the power to decide for himself he chose to stay put: he spent forty years at Teachers College, Columbia University, spurning other positions offered, and built a home at Montrose, New York, at age thirty-three. He died there on August 9, 1949, near age 75, leaving his widow, Elizabeth Moulton, whom he married in 1900, and their four grown children.
The early moving about left Thorndike with pronounced shyness and social uneasiness, helping to make the lonely privacy of research a comfortable world. His educational work also displays a certain nonsocial cast. Unlike the psychologies of the Progressive educators with whom he shared many beliefs, Thorndike's educational psychology was not a social one. To him learning was an essentially private, organic undertaking, something that happened under one's skin, in the nervous system; the "connections" of interest to the teacher were properly those between stimulus and response–not the interactions between individual students, which concern those who view a class primarily as a social group.
During Thorndike's youth the United States fully entered the age of industrialization and urbanization. The mill towns of New England were part of the industrial revolution that was attracting hundreds of thousands of immigrants a year to manufacturing jobs and making Boston, Pittsburgh, Chicago, and New York great, if trouble-plagued, cities. Coming to New York City in 1897 to complete his doctoral studies at Columbia University, Thorndike was to remain there for the rest of his life, except for a brief tenure from 1898 to 1899 as a teacher of psychology and pedagogy at the College for Women of Western Reserve University in Cleveland, Ohio.
It was understandable that an urban setting would be attractive to the modern academic man, particularly to the man of science; it was in the cities that industrial wealth built museums, libraries, and laboratories, and it was there that philanthropic foundations had their headquarters. Such foundations as the Carnegie Corporation of New York, the General Education Board, and the Commonwealth Fund established the Institute of Educational Research at Teachers College, to which Thorndike devoted his energies almost exclusively from 1921. It was at this time that the wealth and centrality of New York City were helping to make Columbia a great national university and its Teachers College the most important center for the training of the leaders in public education in the United States. By 1900 all leading American universities were, like Columbia, in urban settings. Moreover, the leadership of public education nationally was passing into the hands of the superintendents of big-city school systems and to their counterparts in the state capitals and in the Federal Bureau of Education.
By the turn of the century, elementary education in the United States was virtually universal; thereafter, the task was to extend secondary schooling to the entire nation. The need for teachers was great. Although the normal schools, frequently rural institutions, continued to train many teachers, departments of education became common within universities after 1900. Thorndike first arrived at Teachers College in 1899, when its status was changing from that of a private normal school to the education department of Columbia University. Because universities were preeminently places of research, their departments for training teachers and school administrators partook of the prevailing atmosphere favoring scholarly and scientific inquiry. In leaving Western Reserve for Teachers College, Thorndike abandoned a traditional training school for a place which he quickly helped make a center for the scientific study of education and for the training of educational researchers. As its dean, James Earl Russell, recalled: "In developing the subject of educational psychology … for students in all departments, Professor Thorndike has shaped the character of the College in its youth as no one else has done and as no one will ever again have the opportunity of doing" ("Personal Appreciations" 1926, p. 460).
In addition to urban resources and leadership for research and to the prestige accorded science by the universities, there was another incentive for expanding educational research: the widespread desire in educational circles to have teaching recognized as a profession. Schoolmen were aware of the high total of public spending for education and shared the prevailing faith in schools as critical agencies of character training and national development. Even in an occupation marked by low prestige, minimal preparation, a preponderance of women, high turnover, and legal dependence upon boards of laymen, professional status was regarded as an attractive, realizable goal.
One of the characteristics claimed by an occupational group seeking professional status is its possession of a large and growing body of expert knowledge. The function of research was to replace the folklore of the teaching craft with scientifically verifiable assertions. Thorndike acknowledged after thirty years of work that research had yielded only a few answers to the practical questions raised by school operations. He maintained, however, that a true profession awaited those who patiently researched fundamental educational questions. The principal barrier was not, he believed, the limitations of science, but the traditional conservatism and inertia characteristic of institutionalized education.
A Psychology for Educators
At Teachers College, Thorndike taught psychology to large numbers of teachers and school administrators. In his early courses and in such books as his Notes on Child Study (1901a), Principles of Teaching, Based on Psychology (1906), and Education: A First Book (1912), he tried to inform educators of what was already known of human nature and human variation, of what had been written about behavior and learning by such creative psychological thinkers as Scotland's Alexander Bain and William James at Harvard, under whom Thorndike had once studied. Increasingly, however, he turned away from concentrating his efforts on converting teachers to a scientific attitude and away from deducing educational precepts from existing psychological thought. Instead, he began to construct a new educational psychology–one more in keeping with the experimental quantified directions laid out by the "new psychology" being developed in German and American research centers.
The scientific requirement. As much as he admired the brilliance, humane perceptiveness, and stylistic elegance of William James's Principles of Psychology, Thorndike was of that new generation of younger psychologists who, after 1895, sought to sever psychology's ties with "mental philosophy" by rejecting armchair theorizing, avoiding such philosophical concepts as "soul," and opting for the methods, language, and standards of physics and experimental biology. He was deeply impressed by the painstakingly precise observations of animal behavior by Charles Darwin, by the methodological controls in the memory studies of Hermann Ebbinghaus, and by the statistical inventiveness of Sir Francis Galton and Karl Pearson. Discussions in the summer of 1900 with the famed experimentalist Jacques Loeb at the Marine Biology Laboratory at Woods Hole, Massachusetts, finally convinced Thorndike that his talent lay in "doing science," and that he "ought to be shut up and kept at research work" (Jonçich, p. 265).
Lacking mechanical aptitude, Thorndike never incorporated into his research the elaborate instruments found in Wundt's Leipzig laboratory and among Titchener's students at Cornell, or favored by Charles Judd, another important educational psychologist. Thorndike's approach was basically observational and problematic: place the subject in some problem (test) situation–seeking to escape from a confining place, having to rank his attitudes, choosing the correct response among several alternatives to avoid a mild shock–then observe the behavior aroused and report it in quantitative form. The typical Thorndike experiment was a simple paper-and-pencil investigation, like the first he ever attempted: as a Harvard graduate student he tried to measure children's responsiveness to unconscious cues by giving candy rewards to those correctly guessing the number or object he had in mind.
Lessons from animal studies. Despite his typically simple approach, Thorndike is credited with two research techniques basic to modern psychological studies of animal behavior: the maze and the problem box, both of which were invented for his now classic study of learning, Animal Intelligence (1898). A thoroughgoing Darwinist, Thorndike was convinced that, because of evolutionary continuity, the study of animal behavior is instructive to human psychology. Hence, when he had difficulty in securing human subjects, Thorndike switched easily from children to chickens in his Harvard studies.
A significant portion of Animal Intelligence is a critique of the uncontrolled observation and casually acquired anecdotal reportage prevalent in what little comparative psychology existed in the 1890s. The faulty methods, Thorndike declared, contributed spurious data and led to unwarranted interpretations. The most serious error was attributing to animals a higher order of intelligence than would be justified by scientific observations of animal behavior. His own painstaking research with cats and dogs, and later with fish and monkeys, convinced Thorndike that the process of animal learning rested not on some form of reasoning and not even on imitation. Learning depends, instead, upon the presence of some situation or stimulus (S) requiring the animal to make various, more or less random responses (R); as a result of such trial and error, the correct, or most adaptive, response is eventually made (for example, hitting a lever to escape a box or to reach food). The effect produced by the appropriate response is a sort of reward: it may be escape, food, sex, or a release of tension (in animals and humans) or an experienced feeling of success or other learned rewards (in humans alone). The effect acts physiologically, creating or reinforcing a neural connection between that response and the situation which provoked it; repetition of that or a similar stimulus becomes more readily able to produce the previously successful response, and inappropriate responses are forgone. Learning has taken place.
Reward: the key to learning. The basic principle which Thorndike formulated to account for the S-R connection is the law of effect; in the language of such later psychologists as Clark Hull and B. F. Skinner, this is a reinforcement theory of learning.
If, as Thorndike maintained, human behavior represents primordial attempts to satisfy native and learned wants, then an effective, positive, and humane pedagogy is one which facilitates the making of desired and successful responses, forestalls incorrect responses, and is generous with rewards; a poor teaching method, on the other hand, carelessly permits wrong responses and then must punish them to prevent their becoming established as bad habits. Initially Thorndike assumed that reward and punishment were equal opposites, effects evenly capable of causing learning. Reward is preferable since it is more efficient to forestall inappropriate responses by producing and rewarding desired behavior than by punishing incorrect responses; a positive pedagogy is preferable to a punitive one. As a result of empirical studies undertaken in the late 1920s and 1930s, however, Thorndike concluded that he had been mistaken earlier. Punished responses are not weakened as rewarded connections are strengthened; despite common sense and tradition, punishment may actually enhance the probability that an undesired response will be repeated.
Thorndike was virtually the first educator to give theoretical and empirical attention to effect, although reward and punishment had been given practical attention by generations of schoolmen. Still, the pedagogical emphasis at the turn of the century centered on punitive and repressive measures and on fault-finding. In 1906 Thorndike warned teachers that the most common violation of human nature was the failure to reward desired behavior. In propounding the law of effect, then, Thorndike gave a psychologist's support to those educational philosophers, like John Dewey, and those founders of Progressive schools, like Marietta Johnson, who wished to make schools more humane and to have them better relate educational methods to the nature of childhood. However, because of his articulation of another law of learning–the law of exercise–Thorndike's psychology differed from that Progressivist thinking which emphasized spontaneity and favored student selection of activities and freedom from a planned curriculum sequence and from drill. (The law of exercise states that once a given response is made to a particular stimulus, each recurrence of that stimulus tends to recall that response; hence, an S-R bond is being strengthened. The educational implication of the law promotes drill, or practice, of desired responses and careful teacher attention to forming appropriate habits.)
Education as Specific Habit Formation
Accepting William James's views, Thorndike wrote:
Intellect and character are strengthened not by any subtle and easy metamorphosis, but by the establishment of particular ideas and acts under the law of habit …. The price of a disciplined intellect and will is eternal vigilance in the formation of habits ….Habit rules us but it also never fails us. The mind does not give us something for nothing, but it never cheats. (1906, pp. 247–248)
A radical educational theory stressing freedom, spontaneity, inner direction, and "unfolding," one that "stands out of nature's way," was to Thorndike a "something for nothing" pedagogy. In its place, Thorndike's psychology required the careful ordering of learning tasks, as in the Thorndike Arithmetics (1917), which he prepared for school use; practice (exercise, drill) with reward; and measurement of progress through frequent testing, preferably by standardized tests so that more reliable estimates of learning could be had.
Another "something for nothing" educational theory–this one from the conservative, formalistic right wing of educational opinion–was the belief in mental (formal) discipline: that various mental or perceptual faculties are strengthened by being exercised upon some formal, preferably difficult task; that the study of a rigorously logical subject, like geometry, promotes logical behavior; and that practice in accurate copying transfers to other behavior, making one more accurate generally.
Some skepticism about transfer of training had already developed, on a priori grounds, before Thorndike published the first major empirical challenge to this widely held theory. The proponents of more modern subjects–vocational courses, the modern languages, physical education, even the sciences–had attacked formal discipline and faculty psychology because the defenders of the classical studies had based classical domination of the curriculum primarily on the grounds that these difficult and abstruse subjects, which were unappreciated by pupils, had tremendous transferability value, just as lifting the heaviest weights develops muscle power better than lighter burdens do. Between 1901 and 1924, Thorndike's research supported those educational reformers who believed that a subject or skill should be included in the curriculum because of its intrinsic value, and not because of unproved assertions about transfer power.
Education as a Science
In his Educational Psychology, Thorndike wrote: "We conquer the facts of nature when we observe and experiment upon them. When we measure them we have made them our servants" (1903, p. 164). Equally as important as empiricism to Thorndike's psychology was his emphasis on measurement and quantification; poorly prepared by the schools in mathematics and largely self-taught in statistics, Thorndike became the educational world's exponent of the use of science's universal language of description, numbers. His theme was, all that exists, exists in some amount and can be measured. He introduced the first university course in educational measurement in 1902, and two years later he wrote the first handbook for researchers in the use of social statistics, An Introduction to the Theory of Mental and Social Measurements.
Educational and intellectual tests. The movement toward testing was the primary outcome of attempts to translate qualitative statements (Mary seems to be having trouble in reading) into quantitative and comparable terms (In grade 5.6, Mary tests at 4.4 in reading comprehension and 4.7 in vocabulary knowledge). Standardized achievement tests in school subjects were built on centuries of use of teacher-made tests. What the twentieth century added was the standardization necessary for reliability and comparison of results from class to class. Professionally written and administered to thousands of pupils, using norms based on nationwide samples of students, achievement tests were created for every level of schooling, from primary through graduate school, including tests for out-of-school adults at various age levels. In 1921 use of these tests was established when 2 million pupils took standardized tests of academic achievement; thereafter, growth in the use and development of tests was virtually taken for granted. Thorndike contributed several works on construction of tests and devised various tests of his own: rating scales for handwriting, drawing, and composition; tests of oral and silent reading skill, geographical knowledge, English usage, spelling, reading and reasoning; and college entrance tests and law-school entrance examinations.
Intelligence and scholastic aptitude tests have a shorter history but have been even more crucial in shaping school practices (like promotion policies, grouping, and grading) and professional and public thinking. Alfred Binet's point scale, developed in France early in the twentieth century, is the landmark contribution. But before such testing could have great educational or social impact, it was necessary to find means of adapting the individually administered, Binet-type artifact tasks to groups using paper and pencil. This did not come about until World War I, when the U.S. Army commissioned psychologists to prepare and administer tests to aid in classifying recruits. Thorndike was a member of the Committee on Classification of Personnel from 1917 to 1919 and supervised work on the Beta form (the form for illiterate recruits); it and the Alpha form (for literates) were administered to 2 million soldiers by 1919, the world's first effort in the mass measurement of intelligence. Within three years, 1 million schoolchildren took similar tests, many of them the National Intelligence Test which a group of former army psychologists, including Thorndike, had developed. He later devised the CAVD (sentence completion, arithmetic, vocabulary, following directions) intelligence examination and a nonlanguage scale (for illiterates).
Aside from the kind of general intelligence measurements which concern educators most, Thorndike was interested in other types of aptitudes, believing that intelligence is not a unitary or general factor but is constituted of millions of discrete stimulus-response bonds; any intelligence test is simply a selective sample-taking of all the possible learned connections that might be present. Thorndike believed that since individuals differ, primarily by heredity, in their relative ability to form connections (that is, to profit from experience, to learn), and since any one individual is unevenly endowed in the ability to form connections of different types, tests of intelligence-in-general may miss certain aptitudes useful for vocational counseling, hiring programs, or selection of employees for special training programs.
In 1914 Thorndike began devising tests for use in locating persons with clerical aptitudes and interests and thereby fathered personnel-selection psychology in business and industry. In 1918 he headed the wartime search for men with aptitude for learning to fly. To try to prophesy flying success was itself a pioneering venture in a day when hardly a flying school existed in the United States and the aircraft industry was yet unborn. Such wartime experience in measuring aptitudes was continued in Thorndike's later research into vocational guidance for schools. He advocated special efforts and new departures in vocational education for those schoolchildren–perhaps as much as a third of the total–who "may learn only discouragement and failure" from much of the existing curriculum (Jonçich, p. 473). The vocational education movement lagged, however, with the decline of public interest in the 1920s and massive unemployment of the 1930s.
Studying human variation. The new instruments for measuring ability and achievement and especially the widespread use of these instruments inspired new knowledge of and intensified concern with individual differences. "It is useless to recount the traits in which men have been found to differ, for there is no trait in which they do not differ," Thorndike wrote in Individuality (1911, p. 6). The new educational psychology, he said, must reject classical psychology's assumption of a typical mind from which pattern there were only rare departures; it must study individual minds, be a differential psychology which describes, explains, and seeks to make predictions about human variation.
Society's commitment to universal schooling must not, Thorndike believed, obscure its responsibility to every individual and its respect of difference. While psychology will, as a science, search for universal laws explaining human behavior, the pedagogical art, Thorndike believed, must recognize that it is individuals who act, who learn or refuse to learn.
The practical consequence of the fact of individual differences is that every general law of teaching has to be applied with consideration of the particular person … [for] the responses of children to any stimulus will not be invariable like the responses of atoms of hydrogen or of filings of iron, but will vary with their individual capacities, interests, and previous experience. (1906, p.83)
Of these sources of variation, the most important in Thorndike's view was differing capacities–differences caused primarily by genetic inequalities. To the persisting debate about heredity and environment, Thorndike offered comparative studies of twins, siblings, and unrelated individuals, of family histories, and of school eliminations (dropouts). His findings convinced him that heredity is the primary determinant of intellectual difference and, because such other traits as personal morality, civic responsibility, industriousness, and mental health correlate positively with intelligence, that genetic endowment is the critical variable for welfare and social progress. So, in the interest of improving the human gene pool, he espoused eugenics.
In an age when psychoanalysis introduced arresting concepts of the primitive motivations of mankind, when the arts made a virtue of the "natural," when such educational theorists as G. Stanley Hall espoused a naturalism in education which urged teachers to step aside lest they interfere with nature's way, Thorndike offered dissent. Investigations of original nature and its differing expressions in individuals is not an end in itself, he argued. To find that heredity shapes human potential more than does a favorable environment does not end society's responsibility to improve its institutions, any more than the discovery of gravity was an excuse to cease man's efforts to fly. "The art of human life is to change the world for the better," Thorndike wrote in Education: A First Book (1912, p. 1). "Only one thing [in man's nature] is unreservedly good, the power to make it better. This power of learning … is the essential principle of reason and right in the world," he wrote in Educational Psychology (1913–1914, Vol. 1, pp. 281–282).
It is to institutions called schools and universities that modern societies assign most of the formal stimulation of this power of human learning. For his efforts to improve the abilities of educational institutions to capitalize upon learning potential Thorndike received much recognition during his lifetime: the presidencies of and honorary memberships in numerous American and international scientific and educational associations, honorary degrees from many universities, and election to the National Academy of Sciences. A most appropriate award, the Butler Medal in gold, was bestowed upon Thorndike by Columbia University in 1925 "in recognition of his exceptionally significant contributions to the general problem of the measurement of human faculty and to the applications of such measurements to education" (Jonçich, p. 487).
See also: Educational Psychology; Intelligence, subentry on Measurement; Learning Theory, subentry on Historical Overview.
"Annotated Chronological Bibliography, 1898–1925." 1926. Teachers College Record 27 (6):466–515.
Callahan, Raymond. 1962. Education and the Cult of Efficiency. Chicago: University of Chicago Press.
Cremin, Lawrence A. 1961. The Transformation of the School: Progressivism in American Education, 1876–1957. New York: Knopf.
Curti, Merle. 1935. The Social Ideas of American Educators. New York: Scribner.
Jonçich, Geraldine. 1968. The Sane Positivist: A Biography of Edward L. Thorndike. Middletown, CT: Wesleyan University Press.
Lorge, Irving. 1949. "Thorndike's Publications from 1940 to 1949: A Bibliography." Teachers College Record 51 (1):42–45.
Murchison, Carl, ed. 1936. A History of Psychology in Autobiography. Vol. 3. Worcester, MA: Clark University Press.
O'Connell, Geoffrey. 1938. Naturalism in American Education. New York: Benzinger Brothers.
"Personal Appreciations." 1926. Teachers College Record 27 (6):460–465.
"Publications from 1898 to 1940 by E. L. Thorndike." 1940. Teachers College Record 41 (8):699–725.
Thorndike, Edward L. 1898. "Animal Intelligence." The Psychological Review, Monograph Supplements 2, no. 4.
Thorndike, Edward L. 1901a. Notes on Child Study. New York: Macmillan.
Thorndike, Edward L. 1901b. "The Influence of Improvement in One Mental Function Upon the Efficiency of Other Functions." 3 parts. With Robert S. Woodworth. Psychological Review 8 (3):247–261; (4):384–395; (6):556–564.
Thorndike, Edward L. 1903. Educational Psychology. New York: Lemcke and Buechner.
Thorndike, Edward L. 1906. Principles of Teaching, Based on Psychology. New York: A. G. Seiler.
Thorndike, Edward L. 1911. Individuality. Boston: Houghton Mifflin.
Thorndike, Edward L. 1912. Education: A First Book. New York: Macmillan.
Thorndike, Edward L. 1913a. An Introduction to the Theory of Mental and Social Measurements (1904). 2nd edition, revised. New York: Teachers College Press.
Thorndike, Edward L. 1913b. Educational Administration: Quantitative Studies. New York: Macmillan.
Thorndike, Edward L. 1913–1914. Educational Psychology. Vol. 1: The Original Nature of Man. Vol. 2: The Psychology of Learning. Vol. 3: Work and Fatigue, Individual Differences and Their Causes. New York: Teachers College Press.
Thorndike, Edward L. 1917. Thorndike Arithmetics. Books 1, 2, and 3. Chicago: Rand McNally.
Thorndike, Edward L. 1923. Psychology of Algebra. New York: Macmillan.
Thorndike, Edward L. 1928. "Curriculum Research." School and Society 18:569–576.
Thorndike, Edward L. 1935. Thorndike-Century Junior Dictionary. Chicago: Scott Foresman.
Thorndike, Edward L. 1940. Human Nature and the Social Order. New York: Macmillan.
Thorndike, Edward L. 1962. Psychology and the Science of Education: Selected Writings of Edward L. Thorndike, ed. Geraldine Jonçich. New York: Teachers College Press.
Thorndike, Edward L., and Gates, Arthur I. 1929. Elementary Principles of Education. New York: Macmillan.
Thorndike, Edward L., et al. 1928. Adult Learning. New York: Macmillan.
Geraldine Jonçich Clifford
Thorndike, Edward L.
Thorndike, Edward L.
Edward Lee Thomdike (1874-1949) has been rightly called America’s most productive psychologist. He was an indefatigable researcher with wide interests. As important as his capacity for work was his responsiveness to the intellectual and social currents generated by contemporary scientific and technological developments. He once described his career as “a conglomerate amassed under the pressure of varied opportunities and demands,” and he doubted whether being faithful to one’s own plans made science as rich as did following the world’s plans for the scientist. Showing great imaginative and creative powers while living this credo, Thorn-dike so much determined the character of the whole of modern American psychology that his contribution is largely taken for granted.
Historical background . “It is certain that man should try to match his understanding of masses, atoms, and cells by understanding of himself,” Thomdike wrote in Human Nature and the Social Order (1940, p. 97). These words express the sentiment that had ordered not only his career but those of his fellow builders of a science of man since the dawn of the Darwinian age. Just as Bacon, Locke, and Newton had invigorated and redirected the physical sciences, so empiricism and theory building in the biological and social sciences flourished after the publication of Darwin’s Origin of Species in 1859. The doctrine of evolution made man an objective, physical fact in a natural world. The interplay of organism and environment became something to be examined. The biological and psychological processes of the lower animals became relevant to the understanding of man. Interest in the differences between species and in the theory of natural selection generated a curiosity about intraspecies variation; the study and measurement of individual differences grew into a major enterprise of the “new psychology,” especially in the United States. In sum, psychology became “genetic.”
It was feared by some that in the process of becoming genetic, the various social sciences would threaten the existing social order. Others, however, heralded the new sciences of man, modeled as they were upon the spirit and methods of the physical sciences, as basic to a future “social engineering.” They hoped the new sciences would make social problems amenable to solution and would enrich social life, just as the older physical sciences had produced technological and material progress.
To become scientific, however, psychology had to do more than view human nature and institutions as part of a continuum connecting all organic life; it had to renounce armchair theorizing and introspection, develop a new methodology, and imitate the rigor and precision of the established sciences in gathering and interpreting data. The important features of the new approach were experimentation and quantification.
Psychological experimentation received early direction from the German psychophysicists, especially Fechner and Helmholtz. Next, Wilhelm Wundt founded the first psychological laboratory, at Leipzig in 1879. By 1900 such laboratories were common as centers for research and training, especially in the United States. Although they were at first preoccupied with such psychophysical phenomena as sense perception and reaction time, many laboratories later turned to investigations of memory, learning, and problem solving. The methodological prototypes of contemporary American psychological investigation and data gathering were soon evident: G. Stanley Hall’s questionnaires, Thorndike’s problem boxes and paper-and-pencil tests, Charles Judd’s instruments.
By 1900 the “new psychology” was committed to the use of quantification: in the collection of empirical data through counting and measuring, as a statistical method of testing hypotheses, and as the universal language of scientific reporting. Public record keeping was improving rapidly, furnishing a potentially invaluable source of social science data. Still more important were early refinements in statistical methods of manipulating data. Galton developed the correlation coefficient for biology and applied it to psychology; he also used certain conceptual tools of astronomy. Pearson, Spearman, and Cattell contributed early improvements, and Thorn-dike popularized the statistical treatment of social science data, writing the first influential handbook in the field, An Introduction to the Theory of Mental and Social Measurements (1904). Thorndike’s statement, “Whatever exists, exists in some amount and can be measured,” epitomizes his devotion to quantification.
There was yet another component in the intellectual legacy available to Thomdike. American pragmatism was evolving as an articulated philosophical system, and although Thomdike was not an exponent of philosophical pragmatism, he approached science from a pragmatic standpoint. He rejected traditionalism, sentimentalism, and a priori postulates. His theories of value and social action were firmly guided by appraisals of consequences. Furthermore, he helped to give American psychology its behavioristic and functional cast; behavior was to give the social sciences their data, and behavior was to test their theories.
The formative years . Thomdike was born in Williamsburg, Massachusetts, the second of four children. His father, Edward Roberts Thomdike, was first a lawyer, then a Methodist clergyman. The religious environment of the home has been described as rather austere, and the children were active in church activities. As an adult Thomdike helped support the local Methodist church financially but did not attend or require attendance of his children. He believed churches had certain benefits for some people and could perform useful philanthropic tasks; however, he sought to guide his own life by ethical and not religious precepts.
Intellectual pursuits were important in his childhood home: his mother, Abigail Thomdike, described as highly intelligent, may well have encouraged them, and they were certainly stimulated by contact with the several intellectual, sophisticated congregations in the Boston-Cambridge area to which his father ministered. The children had good academic records and won scholarships and other aid, permitting them all to complete college despite the family’s modest finances. The eldest son, Ashley, became a professor of English; Lynn, the third son, a historian; and Mildred, the youngest child, a high school English teacher. At one time or another, all three Thomdike brothers were professors at Columbia University.
During Thorndike’s boyhood the family moved frequently, propelled by the regulation that a Methodist minister must change congregations every few years. Thomdike attended elementary schools in several Massachusetts towns, and high schools in Lowell, Boston, and Providence, R. I. Although his schooling did not suffer because of these frequent moves, the discontinuity in social contacts may have contributed to a certain reticence, extreme self-reliance, and lack of easy sociability apparent in the mature Thomdike. He came to prefer a small circle of cherished friends and disliked routine gatherings, whether they were faculty meetings or national scientific conventions. His work consumed his time and attention, wherever he was, and he found personal contention, competition, and the effort to influence others distasteful, viewing such activities as distractions from the research to which he had devoted himself.
Thomdike entered Wesleyan University in Connecticut in 1891 without having chosen a career. As a boy he had had no interest in science; rather, his early bent had been toward English, a field to which he indirectly returned much later via word counts, semantic and phonetic studies, the authorship of dictionaries, and a theory of speech origins. He pursued the standard classical curriculum at Wesleyan, graduating in 1895 with honors, including membership in Phi Beta Kappa, but still without a commitment to any field. However, he had read William James’s The Principles of Psychology and found its ideas and erudition extremely impressive. A scholarship to Harvard University permitted him to sample several disciplines, and after study under James, Thomdike decided upon psychology. He earned another bachelor’s degree in 1896 and an m.a. in 1897.
Although he had no intention of specializing in comparative psychology, Thomdike began experimental studies of animal learning, convinced that the existing research was impoverished and unsound. A substantial fellowship at Columbia University took him to New York City in 1897 to complete his doctoral study. Columbia offered additional training in biology and statistics, and James McKeen Cattell provided him with laboratory space. The next year Thomdike published his doctoral dissertation, Animal Intelligence (1898-1901). Rarely has a doctoral thesis earned the appellation “classic” yet Thorndike’s study was just that—a classic in comparative psychology, in learning theory, and in psychological methodology.
Academic career . In 1898 Thomdike began teaching at the college for women at Western Reserve University in Cleveland, Ohio. On the recommendation of William James he returned to New York City in 1899 for a one-year trial as instructor in psychology and child study at Teachers College, Columbia University; thus began a forty-year association with that school. In 1901 he became adjunct professor and, in 1904, professor of educational psychology. He took on additional duties in 1922 as director of the division of psychology at the new Institute of Educational Research connected with Teachers College. He retired in 1940 but continued writing and published Selected Writings From a Connectionist’s Psychology in 1949. He died in the early morning of August 9, 1949, at Montrose, New York, a few days short of his 75th birthday. He was survived by his wife, Elizabeth Moulton, whom he had married in 1900, and their four children: Elizabeth Frances, born in 1902, a mathematician; Edward Moulton, born in 1905, and Alan, 1918, both physicists; and Robert Ladd, 1910, a psychologist.
Thomdike was awarded numerous honors during his lifetime: the presidencies of several scientific societies and honorary degrees from American and foreign universities. He was a member of the National Academy of Sciences, the American Philosophical Society, and the American Academy of Arts and Sciences. Foreign recognition brought him
honorary membership in the British Psychological Society, the Comenius Educational Association of Czechoslovakia, and the Leningrad Scientific-Medical Pedological Society. In 1925, for his contributions to psychological measurement and its applications to education, Columbia University awarded Thorndike the Butler medal in gold, granted once every five years for the most distinguished contribution made anywhere in the world to philosophy or to educational theory, practice, or administration. He served on various committees and commissions and was head of the comparative psychology department at the marine biology laboratory at Woods Hole, Massachusetts, from 1900 to 1902.
A theory of learning . For Thorndike’s generation of experimental psychologists, the study of mental processes had the greatest attraction. In Animal Intelligence Thorndike set down what proved to be a lasting framework for his theory of mind and the laws of learning. He brought into the twentieth century the British tradition of “associationism” his own learning theory came to be called “connectionism,” or sometimes “stimulus-response theory.”
The experiment that provided him with the empirical basis of his theory was the following: Observing the behavior of kittens as they tried to escape from simple boxes he had built, Thorndike concluded that it was random trial-and-error behavior that led to the animals’ striking the latch that would open the cage. The desirable consequence was then gradually associated with the one correct movement that would bring it about, and the unrewarded errors were eliminated.
According to Thorndike, mind has no separate identity as such, being merely a collective name for the brain cells, nerve cells, and chemicoelectric operations by which man reacts to internal and external stimulation. Thorndike had an unremitting bias in favor of physiological and biological explanations. In 1940 he reiterated this prejudice when he wrote that doctrines about processes such as learning, instinct, and suggestion—processes that can be translated into terms of conductivity, connection, facilitation, and other “known” neural actions—are “preferable to doctrines which rely upon fields of force, tensions, equilibria, valences, barriers, libido, specialized energies,” all yet un-demonstrated in the neurons (1940, p. 189).
Mind, said Thorndike, is man’s “connection system,” forming a bond between some stimulus— Thorndike preferred the word “situation,” recognizing the complexity of many stimuli—and some response made to it by the learner. All that a man knows, feels, “wants,” or does is dependent upon his having formed a connection between some situation and some response. The term “habit” is equally useful in accounting for a routine motor act or for a lofty abstraction; there are no qualitative differences between simple learning and the so-called higher mental processes.
Thorndike’s “laws of learning” explain the connection processes. His “law of exercise” recalls the. principle of “frequency,” or “use,” found in nineteenth-century association theory: a response made is likely to be made again, merely as a result of having been made before. The “law of effect” states that the consequences (satisfying or not satisfying) of a response will increase or decrease the probability that the connection was formed and that the response will be repeated. Vaguely implied in the writings of Alexander Bain and the British animal psychologist C. Lloyd Morgan, the law of effect was made an articulate and heuristic principle of learning by Thorndike. Although the law confirmed common-sense observations, Thorndike’s proposition that consequences can work back upon a stimulus-response connection neurologically has provoked considerable debate and experimentation.
Thorndike’s work on the amount and explanation of the transfer of training, beginning with the landmark Thorndike-Woodworth experiments published as “The Influence of Improvement in One Mental Function Upon the Efficiency of Other Functions” (Thorndike & Woodworth 1901), also sparked controversy. His research showed that learning any one skill has little effect upon the rate or ease of learning another, even for quite similar tasks. Furthermore, the small amount of transfer that does occur, he maintained, can be credited to the presence of “identical elements” in the two tasks or situations; it is not the result of insight or reason or conscious application of principles. Since educators argued that school subjects as disparate as the classical languages, mathematics, and manual training should all be included in the curriculum because of their “formal discipline” powers—their ability to train the memory, sharpen perceptions, and improve attention—considerable opposition was aroused. On the other hand, those educators who pleaded for a curriculum embodying content and activities that were highly specific, practical, and obviously relevant to daily life were encouraged by Thorndike’s results.
Determinants of human abilities . Thorndike believed that intellectual and achievement differences between people are quantitative, not qualitative. Individuals differ in the number and complexity of the connections that they possess and, beyond that, in their capacity to form connections. He held
heredity to be primarily responsible for human equality. He scorned environmental explanations and was interested in eugenics as a means of improving human beings and society, thus perpetuating the views of Galton, for one. Furthermore, Thorndike supported an established American belief: expressed in common-sense terms, it asserted the triumph of character over circumstances, the faith that the ingredients of success are in a man and not around him. The cultural ethos had emphasized character, perseverance, intuition, and good judgment; Thorndike added a high order of intelligence as a basic ingredient in the American success story.
With refinements in measures of individual variation and their more extensive use, the heredity-environment debate became more heated. The validity of political, educational, welfare, and religious policies was at stake, and social science research was called upon to justify opposing views. All through the years when environmental theories were dominant—owing partly to social reform movements and partly to the cogency of Pavlovian conditioning theories and of Watson’s brand of behaviorism—Thorndike held his ground. While his later writings acknowledged the importance of chance factors, such as opportunity, in determining whether innate potentialities would be realized, he consistently believed that heredity was prepotent and that the egalitarian vision of a true parity— whether attempted through education or a welfare state—was indeed just a dream.
Practical applications . In 1917-1918 Thorndike served on the Committee on Classification of Personnel for the United States Army, traveling between Washington, D.C., and his teaching duties in New York. The committee was responsible for the “Army Alpha” project, which was the first mass testing of intelligence, and which subsequently stimulated testing in schools, colleges, and industry. (The ultimate result of his and others’ efforts was the Army General Classification Test used in World War n.) Large numbers of people were trained in test construction and administration. The terms “intelligence quotient” (IQ) and “mental age” entered popular language. Furthermore, public attention was called to the great and inborn physical, intellectual, and educational differences found in the population and to the inequalities resulting from regional isolation and inadequate local schooling, which failed to develop the natural abilities of thousands of people. Adult education programs were invigorated when Thorndike’s investigations of adult learning in the 1920s showed that innate and individual factors and not age are the determinants of the amount and quality of achievement and the ability to continue learning.
Thorndike contributed both directly and indirectly to the development of efficient, scientifically based schooling, the desire for which had begun late in the nineteenth century. He was influential as a teacher of psychology to teachers: early books like Notes on Child Study (1901), The Principles of Teaching Based on Psychology (1906), and Education: A First Book (1912) turned teachers toward a concern for human nature and the learning process and enlisted their support for the scientific movement in education. Thorndike’s numerous articles reporting studies using schoolchildren, school subjects, and various testing approaches were published between 1900 and 1925. The 1907 Annual Report of the U.S. Bureau of Education disclosed the statistics on pupils leaving school before graduation, dramatizing the inadequacies of existing programs and the extent of school retardation and thus giving aid to reformers of curriculum and teaching methods. Thorndike contributed much to the growing awareness of individual differences and to plans for educating the whole range of American children. The main divisions of modern educational psychology—measurement, learning, and individual differences—correspond to Thorndike’s own major interests.
Thorndike was active in the preparation of school materials and tools; various achievement scales, especially for handwriting and drawing, were one result. The psychology of school subjects became a preoccupation of some educational psychologists, and the Thorndike arithmetic and algebra texts were in widespread use. He also prepared college entrance examinations, a test for selecting students for the Columbia School of Law, and one of the best regarded of intelligence tests, the CAVD scale. (The acronym stands for sentence completion, arithmetical reasoning, vocabulary, and the ability to follow directions.) His counts of word usage established the basic vocabulary now used in virtually all school reading books, spellers, and spelling lists, and on achievement tests.
The Teachers College program of training in statistics and measurement as applied to education inspired other attempts to create a scientific approach to curriculum selection and to school administration. Experimental schools multiplied and research on city schools increased. Thorndike would have taken great exception to the poor controls, naivete, and pretentious pseudoscientism that often prevailed; nevertheless, the sponsors of these activities looked to Thorndike and to his institution for stimulation.
Theoretical work . There is much evidence to confirm the psychologist Irving Lorge’s description of Thorndike, his teacher and close friend, as a great eclectic. This can partly be attributed to Thorndike’s responsiveness to opportunities and requests to conduct studies. It is also related to the fact that the direction of Thorndike’s interests was determined not exclusively by the logic of inquiry but also by the nature of the criticisms that were made of his work: when his work was challenged, he sought new evidence to support his theories, and this search for new evidence often led him in unexpected directions.
It was a challenge to the “law of effect” that led to Thorndike’s discovery of the “spread,” or “scatter,” phenomenon. He devised numerous experiments: for example, subjects were asked to supply missing words in a long series of statements, the experimenter rewarding certain answers by saying “right” and punishing others by saying “wrong,” according to a predetermined key. Each series was repeated two or three times in succession. Predictably, the studies revealed that words that were rewarded were repeated—the connection was strengthened; they were “learned.” Surprisingly, however, some words called “wrong” were also repeated, the more so the nearer in distance they were to the “right” words; words in the series just before and just after the rewarded words received the maximum scatter effect from the reward’s power in strengthening responses, while those four or five words removed from the rewarded word were barely affected. Such findings tended to corroborate Thorndike’s contention that the law of effect operates irrespective of reason, in a mechanical or automatic fashion. The repetition of an action called “right” can be considered evidence that reason guides learning. But repetition of erroneous responses as a result of symbolic rewards, and irrespective of the subject’s understanding or insight, seriously challenges the cognitive psychologist’s basic thesis. Thorndike regarded this as his most important contribution to scientific advancement.
Further evidence of Thorndike’s continued growth was his reversal of his early views on reward and punishment in learning. He first believed these to be simple opposites within the law of effect. Later investigation showed that reward is the more effective and stable “confirming” agent; punishment may sometimes strengthen a connection rather than consistentiy weaken it. He also showed that belief in a simple hedonism was unwarranted; small satisfactions usually work as well as large rewards. The implications of his findings about reward and punishment were neglected, Thorndike complained, by educational, governmental, and penal institutions and by welfare agencies.
In 1929 Thorndike surprised the Ninth International Congress of Psychology, meeting at Yale University, by announcing that he had long erred in maintaining that “exercise” and “effect” were companion laws of equal potency. He had come to believe instead that exercise—mere repetition of a response—was of minor importance in explaining the formation and strengthening of connections. As a result of this new conviction, he began a massive experimental program. A series of books published in the 1930s, Human Learning (1931), The Fundamentals of Learning (1932), and The Psychology of Wants, Interests, and Attitudes (1935), reveal a theory trying to come to terms with data. As Leo Postman has observed, Thorndike clearly did not consider connectionism a finished product (Postman 1962, pp. 340, 349).
It was in the 1920s and 1930s that psychology became most highly fragmented into conflicting schools, each differing in its research methods, problems studied, and in its experimental results. New principles—like “belongingness,” an explanation of the way certain things are connected by the learner because they “seem to go together”—were used by Thorndike merely to account for variations in the operations of his basic and still mechanistic principles of learning. Similarly, he considered “mental set”—the observed tendency to respond to some things in an environment of possible stimuli and to disregard other things—to be the residue of established stimulus-response bonds still operating to condition the making of new connections. He continued to concede little to gestaltist criticism and what he called the “possibly sound elements of Freudianism” (1940, pp. 336 ff.). His theoretical pre-eminence in the 1930s was unquestioned; as Edward C. Tolman observed:
The psychology of animal learning—not to mention that of child learning—has been and still is primarily a matter of agreeing or disagreeing with Thorndike, or trying in minor ways to improve upon him. Gestalt psychologists, conditioned-reflex psychologists, sign-gestalt psychologists—all of us here in America seem to have taken Thorndike, overtly or covertly, as our starting point. And we have felt very smart and pleased with ourselves if we could show that we have, even in some very minor way, developed new little wrinkles of our own. (1938, p. 11)
Interest in other social sciences . The economic and social conditions of the 1930s stimulated the social sciences. The Carnegie Corporation, for example, offered Thorndike a large grant, which enabled him to apply his methods and theories to a
study of various social problems. While he was not interested in direct political activity, he had strong conservative and individualistic views, which emerged clearly in his writings of this period. At this time he was no longer primarily concerned with psychological theory. For instance, using census data and other statistics, he tried to analyze cities as he had earlier studied individuals. In Your City (1939) he presented the results and concluded that “good” cities are the result of good people whom they attract; good cities do not create good people. This was yet another expression of his hereditarian position; it had no discernible influence upon urban sociology.
His massive Human Nature and the Social Order (1940) was a compendium of information about human abilities, behavior, and wants, general psychological principles, and the facts of individuality. He contended that the social sciences require such knowledge of how humans behave, what people can be and do, and what they want to be and do, and he suggested applications of this knowledge to many fields: economics, government, philanthropy, religion, law, ethics. In 1943 he wrote Man and His Works, which was similar in conception but on a far smaller scale.
Thorndike’s direct influence upon the social sciences other than psychology was probably small. However, the rapid growth of psychology may have indirectly favored development of the other behavioral fields. Some social psychologists now use Hullian principles, a synthesis of Thorndike and Pavlov; but they often take learning theory largely for granted. Thorndike himself always made motivation secondary to learning: men act the way they do because such behavior has previously been reinforced. Thorndike’s influence on later work with attitude scales is doubtful. Statistical training has only lately become a common part of the sociologist’s education. And anthropologists and sociologists have studied intelligence testing primarily for what it reveals about cultural bias.
Major differences in points of departure between the several social sciences and the kind of psychology that interested Thorndike help explain this independent development. According to Thorndike, individual behavior, with all its variations, takes precedence over language, customs, and laws as a determinant of social action. This view of man contrasts with that of the sociologists, namely, that men are members of social groups and that although all men are not basically the same, their similarities are more crucial than their differences.
Another important distinction between psychology and the other social sciences is the differential emphasis given to environmental factors. Many social scientists have concluded, as a result of comparative cultural studies, that psychologists have exaggerated the importance of inherited qualities. The hereditarian Thorndike, however, continually saw all environments as the product of the genetic equipment of their inhabitants.
On one issue—the future possibilities of social science—there was common, widespread agreement among social scientists; it is reflected in Thorndike’s reiteration in 1940 of his lifelong certainty that “the welfare of mankind now depends upon the sciences of man …” (1940, preface).
[For the historical context and subsequent development of Thorndike’s ideas, seeintelligence and intelligence testing; learning; and the biographies of many of the psychologists mentioned in the text.]
(1898-1901) 1911 Animal Intelligence: Experimental Studies. New York: Macmillan.
(1901) 1903 Notes on Child Study. 2d ed. New York: Macmillan.
1901 Thorndike, Edward L.; and Woodworth, Robert S. The Influence of Improvement in One Mental Function Upon the Efficiency of Other Functions. Psychological Review 8:247-261, 384-395, 553-564.
(1904) 1913 An Introduction to the Theory of Mental and Social Measurements. 2d ed. New York: Columbia Univ., Teachers College.
1906 The Principles of Teaching Based on Psychology. New York: Seiler.
1912 Education: A First Book. New York: Macmillan.
(1913-1914) 1921 Educational Psychology. 3 vols. New York: Columbia Univ., Teachers College. * Volume 1: The Original Nature of Man. Volume 2: The Psychology of Learning. Volume 3: Mental Work and Fatigue and Individual Differences and Their Causes. Part 2 of Volume 3 first appeared in 1903 as Educational Psychology.
1931 Human Learning. New York: Appleton.
1932 The Fundamentals of Learning. New York: Columbia Univ., Teachers College.
1933 An Experimental Study of Rewards. Teachers College Contributions to Education, No. 580. New York: Columbia Univ., Teachers College.
1935 The Psychology of Wants, Interests, and Attitudes. New York: Appleton.
1936 Autobiography. Volume 3, pages 263-270 in A History of Psychology in Autobiography. Edited by Carl Murchison. Worcester, Mass.: Clark Univ. Press.
1939 Your City. New York: Harcourt.
1940 Human Nature and the Social Order. New York: Macmillan.
1943 Man and His Works. Cambridge, Mass.: Harvard Univ. Press.
Psychology and the Science of Education: Selected Writings. Edited by Geraldine M. Joncich. New York: Columbia Univ., Teachers College, 1962. -” Published posthumously. Contains writings first published between 1901 and 1939.
Selected Writings From a Connectionist’s Psychology. New York: Appleton, 1949. -” Contains writings first published between 1913 and 1946.
Curti, Merle E. (1935) 1959 Edward Lee Thorndike, Scientist: 1874-1949. Pages 459-498 in Merle E. Curti, The Social Ideas of American Educators. New ed., rev. Paterson, N.J.: Littlefield.
Edward L. Thorndike: 1874-1949. 1949 Teachers College Record 51:26-45. -* See especially pages 42-45 for a bibliography of Thorndike’s publications from 1940-1949.
Garrett, Henry E. (1930) 1951 Great Experiments in Psychology. 3d ed. New York: Appleton. * See especially “Thorndike’s Law of Learning,” pages 40-62.
Goodenough, Florence L. 1950 Edward Lee Thorndike. American Journal of Psychology 63:291-301.
Hullfish, H. Gordon 1926 Aspects of Thorndike’s Psychology in Their Relation to Educational Theory and Practice. Columbus: Ohio State Univ. Press.
In Honor of Edward Lee Thorndike. 1926 Teachers College Record 27:457-586. -> An annotated, chronological bibliography of Thorndike’s publications appears on pages 466-515.
In Honor of E. L. Thorndike. 1940 Teachers College Record 41:695-788. -> See especially pages 699-725 for a bibliography of Thorndike’s publications from 1898-1940.
Woodworth, Robert S. 1952 Edward Lee Thorndike, 1874-1949. Volume 27, pages 209-237 in National Academy of Sciences, Washington, D.C., Biographical Memoirs. Washington: The Academy.
Boring, Edwin G. (1929) 1950 A History of Experimental Psychology. 2d ed. New York: Appleton.
Hilgard, Ernest R.; and Bower, Gordon H. (1948) 1966 Theories of Learning. 3d ed. New York: Appleton.
Orata, Pedro T. 1928 The Theory of Identical Elements. Columbus: Ohio State Univ. Press.
Postman, Leo 1962 Rewards and Punishments in Human Learning. Pages 331-401 in Leo Postman (editor), Psychology in the Making: Histories of Selected Research Problems. New York: Knopf.
Tolman, Edward C. 1938 The Determiners of Behavior at a Choice Point. Psychological Review 45:1-41.