[1][2] A Review of General Psychology survey, published in 2002, ranked Thorndike as the ninth-most cited psychologist of the 20th century.

Through his contributions to the behavioral psychology field came his major impacts on education, where the law of effect has great influence in the classroom.

The younger, Lynn, was a medievalist specializing in the history of science and magic, while the older, Ashley, was an English professor and noted authority on Shakespeare.

In 1898 he completed his PhD at Columbia University under the supervision of James McKeen Cattell, one of the founding fathers of psychometrics.

In 1899, after a year of unhappy initial employment at the College for Women of Case Western Reserve in Cleveland, Ohio, he became an instructor in psychology at Teachers College at Columbia University, where he remained for the rest of his career, studying human learning, education, and mental testing.

[6] During the early stages of his career, he purchased a wide tract of land on the Hudson and encouraged other researchers to settle around him.

[5] Thorndike was a pioneer not only in behaviorism and in studying learning, but also in using animals in clinical experiments.

[7][verification needed] Thorndike was able to create a theory of learning based on his research with animals.

[11] Thorndike's puzzle boxes were arranged so that the animal would be required to perform a certain response (pulling a lever or pushing a button), while he measured the amount of time it took them to escape.

"[13] Thorndike meant to distinguish clearly whether or not cats escaping from puzzle boxes were using insight.

He reasoned that if the animals were showing insight, then their time to escape would suddenly drop to a negligible period, which would also be shown in the learning curve as an abrupt drop; while animals using a more ordinary method of trial and error would show gradual curves.

Thorndike put his testing expertise to work for the United States Army during World War I, participating in the development of the Army Beta test used to evaluate illiterate, unschooled, and non-English speaking recruits.

[17] He argued that "selective breeding can alter man's capacity to learn, to keep sane, to cherish justice or to be happy.

"[18] He stated:I hope to have made it clear that we have much to learn about eugenics, and also that we already know enough to justify us in providing for the original intellect and character of man in the future with a higher, purer source than the muddy streams of the past.

It is a noble thing that human reason, bred of a myriad unreasoned happenings, and driven forth into life by whips made aeons ago with no thought of man's higher wants, can yet turn back to understand man's birth, survey his journey, chart and steer his future course, and free him from barriers without and defects within.

Until the last removable impediment in man's own nature dies childless, human reason will not rest.

Thorndike was among some of the first psychologists to combine learning theory, psychometrics, and applied research for school-related subjects to form psychology of education.

Thorndike opposed the idea that learning should reflect nature, which was the main thought of developmental scientists at that time.

Although Thorndike's description of the relation between reinforcers and punishers was incomplete, his work in this area would later become a catalyst in further research, such as that of B.F.

[24] While conceding that society could "complicate or deform"[25] what he believed were inborn differences, he believed that "if we [researchers] should keep the environment of boys and girls absolutely similar these instincts would produce sure and important differences between the mental and moral activities of boys and girls".

[26] Indeed, Watson himself overtly critiqued the idea of maternal instincts in humans in a report of his observations of first-time mothers struggling to breastfeed.

Selected sources extrapolated from Appendix A include: In the preface to the third book, Thorndike writes that the list contained therein "tells anyone who wishes to know whether to use a word in writing, speaking, or teaching how common the word is in standard English reading matter" (p. x), and he further advises that the list can best be employed by teachers if they allow it to guide the decisions they make choosing which words to emphasize during reading instruction.

If a word is not on the list but appears in an educational text, its meaning only needs to be understood temporarily in the context in which it was found, and then summarily discarded from memory.

[33] His influence on animal psychologists, especially those who focused on behavior plasticity, greatly contributed to the future of that field.

His work represents the transition from the school of functionalism to behaviorism, and enabled psychology to focus on learning theory.

[11] His work on motivation and attitude formation directly affected studies on human nature as well as social order.

[11] Thorndike's research drove comparative psychology for fifty years, and influenced countless psychologists over that period of time, and even still today.

[38] His law of effect and puzzle box methodology were subjected to detailed criticism by behaviorists and many other psychologists.

[40] Because of his "racist, sexist, and antisemitic ideals", amid the George Floyd protests of 2020, the Board of Trustees of Teachers' College in New York voted unanimously to remove his name from Thorndike Hall.