“Whatever exists at all exists in some amount. To know it thoroughly involves knowing its quantity as well as its quality” (Thorndike, 1918, p. 16). This quotation captures the attitude that E. L. Thorndike brought to the study of education. The hallmark of his work was his abiding faith in the quantifiability of all aspects of human experience.


Edward Lee Thorndike was born in Williamsburg, Massachusetts, on August 31, 1874, to Edward Roberts and Abbie (Ladd) Thorndike. E. R. Thorndike was a Methodist minister who served churches in Maine and Massachusetts. Perhaps in reaction to a strict religious upbringing, throughout his life, E. L. Thorndike favored science over religion.

Upon graduation from Wesleyan University in 1895, Thorndike went to Harvard University to study with William James and begin his psychological studies of learning. He soon moved from Harvard to James McKeen Cattell's lab at Columbia University where he undertook his famous puzzle box studies with cats. After earning his doctorate Thorndike spent a year at Western Reserve University before becoming a member of the founding faculty at Teachers College (TC), Columbia University, in the fall of 1899. He remained at TC until his retirement in 1940, publishing approximately 500 books, monographs and papers. (For a list of publications, see Gates, 1949.)

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Thorndike married Elizabeth Moulton on August 29, 1900. They had four children, all of whom earned PhDs. The second son, Robert L., followed in his father's footsteps at Teachers College.

E. L. Thorndike's work was widely recognized within his own lifetime. He was elected president of the American Psychological Association (1912), the American Association for the Advancement of Science (1933), and the Psychometric Society (1936). Cattell ranked him first among American psychologists in a 1921 poll for American Men of Science. Thorndike died of a massive cerebral hemorrhage on August 9, 1949.


E. L. Thorndike formulated a theory of mental associations called connectionism. He believed that the central nervous system was the basis of all behavior. Learning took place when connections were formed between neurons. The purpose of education was to facilitate the formation of desirable connections.

Thorndike was fascinated with individual differences, trying to measure them, explain them, and use them for prediction. He believed that science could solve human problems, and he applied scientific method to problems of education. Much of his career was spent trying to develop methods to measure individual differences and to use these measurements to make education more efficient and successful.

Thorndike set out to place education on a sound scientific footing. The prevalent educational practice in 1900 was the doctrine of mental discipline. Curriculum was founded on opinion, not evidence. Based on his studies he concluded that education must be conducted in the subject to be learned and tailored to the ability levels of the students. He continued his pursuit of quantification and scientific method in education in one of the first books on psychological and educational measurement (Thorndike, 1904).

In addition to his efforts to make education more efficient and scientifically sound, Thorndike expended considerable effort from 1900 to 1925 in developing measures of intellect. Beginning in 1903, he and his students developed a wide variety of measures of human abilities, culminating in the CAVD, a “test constructed (in 1922–1925) as a sample of what a measuring instrument for a mental ability should be” (Thorndike, 1949, p. v.). The acronym stood for Comprehension, Arithmetic, Vocabulary and Direction following, four of the more important dimensions of intellect in Thorndike's view.

In the 1930s, Thorndike turned his attention to problems of lexicography, and in this work, he revolutionized the way dictionaries were produced. For years he had been keeping records of the frequency of word usage in the English language. He used these counts to determine which words to include in his dictionaries and what the order of definitions should be. He also required that each word be defined only using words that were more frequently used than the word being defined. All modern dictionaries now apply these principles.

E. L. Thorndike's influence on education and psychology is so pervasive that it is hard to detect. He pioneered the scientific study of education and made major contributions to the measurement of human abilities, comparative psychology, and social psychology. The hundreds of students he taught have spread his ideas throughout American education and psychology. Most 21st-century education faculty can trace their intellectual ancestry to him through their mentors. A full biography of E. L. Thorndike is available in Joncich (1968).

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Thorndike, E. L. (1903). Educational Psychology. New York: Lemcke & Buechner.

Thorndike, E. L. (1904). An introduction to the theory of mental and social measurements. New York: Science Press.

Thorndike, E. L. (1913). An introduction to the theory of mental and social measurements. New York: Teachers College, Columbia University Press.

Thorndike, E. L. (1918). The nature, purposes, and general methods of measurement of educational products. In S. A. Courtis (Ed.), The Measurement of Educational Products (17th Yearbook of the National Society for the Study of Education, Pt. 2. pp. 16–24). Bloomington, IL: Public School.

Thorndike, E. L. (1949). Selected Writings from a Connectionist's Psychology. New York: Appleton-Century-Crofts.


Gates, A. I. (1949). The writings of Edward L. Thorndike. Teachers College Record, 51, 28–31.

Joncich, G. (1968). The sane positivist: A biography of Edward Lee Thorndike. Middletown, CT: Wesleyan University Press.