Introduction

Edward Lee Thorndike (1874–1949) was an American psychologist during the turn of the century. He is well known for his early behavioral animal studies, but most of his work throughout his career focused on learning, educational philosophies, intelligence, and test theory.

Personal Life and Academic Career

Edward Lee Thorndike was born on August 13, 1874 in Williamsburg, Massachusetts to Edward R. Thorndike and Abbie (Ladd) Thorndike. His father was a prominent Methodist minister with congregations in both Maine and Massachusetts. Thorndike, along with his two brothers, Ashley and Lynn, and his sister, Mildred, grew up in a devoutly Christian household, though they were likely influenced by their mother’s fundamentalist beliefs as well. They were raised with expectations of education and excellence, and all four went on to win academic scholarships and pursue academic careers: Ashley as a professor of English, Lynn as a historian, Mildred as a high school teacher, and Edward Lee as a psychologist and educator.

Throughout his childhood, Thorndike’s family moved frequently around New England as his father followed the church’s request to move congregations. This may have contributed to Thorndike’s noticeable shyness and social uneasiness – two traits that may have influenced his pursuit of research and learning. As he grew up, Thorndike’s views of the world shifted away from his religious upbringing and toward a strictly empirical and science-based perspective. He pursued his education with the same passion and dedication that his father demonstrated toward the church, and he graduated in 1895 from Wesleyan University in Middletown, Connecticut with a bachelor’s degree and an impressive academic record.

Thorndike’s budding interest in psychology was strongly influenced by William James’ The Principles of Psychology, and he applied to and was accepted for graduate training in this field at Harvard University. Thorndike worked under James himself for 2 years, initially studying learning in children but switching to animal work after a failed “mind-reading” study. After 2 years Thorndike left Harvard for Columbia University. He worked with James McKeen Cattell, who was researching individual differences in human intelligence at the time.

Thorndike spent his graduate years studying animal learning and intelligence, and although previous psychological researchers relied on philosophical debates to study psychology, Thorndike focused on incorporating empirical scientific methodology similar to that used in physics and biology. He relied on controlled observation via empirical testing techniques and demonstrated a particular aptitude for developing experimental paradigms. He developed two novel research techniques that have become commonplace in modern psychology and animal research, the maze and the puzzle box. The latter was developed and utilized for his doctoral thesis, “Animal intelligence: An experimental study of the associative processes in animals,” for which he was awarded his doctorate in 1898. Later, he incorporated this work in his publication Animal Intelligence in 1911 (Thorndike 1898, 1913).

Thorndike married Elizabeth Moulton on August 29, 1900. They had four children, all of whom followed in their father’s footsteps of academic pursuits and earned doctoral degrees in science or mathematics. After graduating with his doctoral degree at the age of 24, Thorndike was employed as an assistant professor for 1 year at the College for Women of Case Western Reserve in Cleveland, Ohio. However, he was unhappy there and moved back to Columbia University in New York, where James E. Russell was working to transition the Teachers College into affiliation with the education department at Columbia. Thorndike became one of the college’s founding faculty members and helped establish it as a base of scientific inquiry on education and the training of educational researchers. He remained there for the rest of his career, dedicating himself to the study of human learning, education, and mental testing. He retired in 1940 but continued to work until his death. Thorndike died of a stroke at his home in Montrose, New York, on August 9, 1949.

Research Interests and Major Contributions

Thorndike’s contributions spanned the fields of learning, educational science, intelligence, and test theory. Thorndike is well known for founding connectionism theory, a theory that states that learning occurs due to connections formed between specific stimuli (S) and responses (R). This is often referred to as the original S-R framework of behavioral psychology. Thorndike’s early puzzle box experiments and early animal work on cats, dogs, and chicks allowed him to empirically plot learning curves for what animals learned, how quickly the learning occurred, and how long the learning was retained. Results from these experiments led Thorndike to propose three primary laws that predicted behavioral associations or connections: the law of effect, the law of readiness, and the law of exercise. The law of effect stated that in response to a stimulus (S), responses (R) that were closely followed by a satisfying result (or reward) were most likely to become ingrained as a behavioral pattern and would occur more often in the future in response to the same stimulus. The law of readiness explained that a pattern of responses could be linked together to obtain the achievement of a goal (which would result in annoyance if prevented). The law of exercise stated that frequent connections of stimulus and response would result in more strongly established behavioral patterns.

Thus, Thorndike concluded that animal learning is not the result of logical reasoning or imitation, but that it is a basic trial and error process of behavioral responses, only some of which lead to beneficial or desired outcomes. Influenced by Charles Darwin’s work on evolution, Thorndike was convinced that the results of his animal research were not limited to the specific species he studied. Instead, he believed that connectionism theory was equally applicable to both animal and human learning, and he soon shifted his research focus away from animal studies in favor of studying learning in humans.

Later, after earning his doctoral degree at Columbia University, Thorndike expanded his interests in learning to include the process of education itself. He applied connectionism theory to multiple fields of education, including spelling and reading (Thorndike 1921), mathematics (Thorndike 1922), the measurement of intelligence (Thorndike et al. 1927), and adult learning (Thorndike et al. 1928). He also explored the impact of both reward and punishment on behavioral patterns (or learning) and initially proposed that both reward and punishment were equally effective methods of learning. However, in response to empirical work performed in the 1920s and 1930s, he found that punishment could increase the likelihood of an undesired response. This research on learning and behavioral patterns provided both theoretical and empirical evidence for educators who were, at that time, striving to shift educational systems away from punitive policies and toward teaching methods emphasizing encouragement and praise.

Thorndike’s educational philosophies were based primarily in his law of effect and law of exercise. He proposed that sole utilization of punitive measures, the primary method in schools at the time, was not an effective way of establishing S-R bonds. Instead, he proposed that pairing educational tasks with reward would establish the connections necessary for learning and that repetition of this would strengthen that bond. Thorndike proposed that this S-R bonding method of learning would instill intrinsic motivation in students to succeed, and he referred to this overall conceptualization of learning as the law of habit.

Thorndike was not the first to question the punitive focus of educational environment at the time. Some educational philosophers had proposed radical philosophy changes and directives in response to punitive learning environments that emphasized student-directed explorations of topics in an unstructured and unregulated manner. However, Thorndike also adamantly opposed this style of teaching and insisted that, because of the law of habit, regular direction, practice, and repetitious drilling was necessary to strengthen S-R bonds. To put this theory into practice, Thorndike developed structured lessons for school use incorporating reward.

As Thorndike’s learning theories became widespread among educational philosophers, he became aware of problems with regard to how achievement and progress were measured in education. This served as the catalyst for his interest in test theory and development. Assessment in educational settings had been largely subjective, unstandardized, and teacher developed, and Thorndike worked to create more objective and standardized forms of measuring learning, educational progress and achievement, and intelligence in general.

Although Thorndike was largely self-taught in statistics, his dedication to theory-based quantification led him to develop the first university course on educational measurement in 1902. Soon after, he wrote a handbook on social statistics (An Introduction to the Theory of Mental and Social Measurement), widely considered to be the first textbook on test theory. In addition, Thorndike developed a plethora of standardized scales designed to measure a wide range of attributes, including handwriting and drawing, oral and silent readings skills, English language proficiency, and logical reasoning. He soon became interested in developing and utilizing standardized examinations for entrance into colleges and law schools and aptitude tests for personnel selection such as clerics and pilots.

His experience with developing standardized testing procedures led to his selection for the United States Army’s Committee of Classification of Personnel in 1917, where he was tasked with developing and administering intelligence tests to aid in classifying recruits. He played a significant role in developing the Alpha and Beta intelligence tests during World War I, laying the foundation for more improved intelligence tests in the future. While themes of intelligence and “intellect” appeared throughout both his early animal work and his education research, the experience of developing these tests inspired him to pursue research on human intelligence in the context of stimulus-response (S-R) learning. Specifically, Thorndike proposed that intelligence itself was not a unitary construct but was based on the strength of varying groups of S-R bonds. However, he also thought that individuals differed in their naturally occurring ability to form these bonds. This led him to conduct a number of comparative studies of siblings, twins, and unrelated individuals which convinced him that differences in the ability to form S-R bonds (i.e., what he considered intellectual differences) was largely based in genetics.

Thorndike eventually proposed four general dimensions to intelligence: altitude (difficulty of a task), width (the variety of tasks within a given difficulty), area (a function of both width and altitude), and speed (the number of tasks completed in a given time). He emphasized altitude above the other dimensions and considered this particular factor to be largely influenced by genetics. This lay in stark contrast to Charles Spearman’s single factor of intelligence, which was proposed in 1904. Thorndike and Spearman engaged in a lifelong debate over the fundamental nature of intelligence, a debate that continues in contemporary psychology.

Conclusion

Overall, Thorndike’s contributions to multiple scientific fields, including learning, education, test theory, and intelligence, resulted in him being one of the most productive American psychologists during the beginning of the twentieth century. Throughout his career, he published over 500 books and articles, many of which revolutionized the field at the time. He was the recipient of many awards and accolades throughout his professional career, which reflect the impact his work had across academic disciplines. In 1912 he was elected as president of the American Psychological Association, and in 1917 he became one of the first psychologists to be admitted to the National Academy of Sciences. In 1921 he was ranked number 1 in American Men of Science, and in 1934 he became the president of the American Association for the Advancement of Science, the only social scientist to do so. Although his work spanned a wide variety of fields, he considered himself a psychologist first and foremost. Leaving behind a lifetime’s worth of impactful contributions to learning, education, testing, and intelligence, Thorndike provided foundational understanding that continues to impact modern research in these fields.