Edward L. Thorndike was a US psychologist who did work on learning and education at the beginning of the 20th century.
Among Thorndike's most famous contributions were his research on cats escaping from puzzle boxes, and his formulation of the Law of Effect. Both of these, then under the rubric of 'instrumental learning,' prefigured operant conditioning work done by the radical behaviorists, whose notion of reinforcement was a clever conceptual reworking of the Law of Effect.
The puzzle box experiments (performed in William James' basement - because Harvard didn't want animals in its buildings!) were motivated in part by Thorndike's dislike for statements that animals made use of extraordinary factulties such as insight in their problem solving: "In the first place, most of the books do not give us a psychology, but rather a eulogy of animals. They have all been about animal intelligence, never about animal stupidity." (Animal Intelligence, 1911). (Much the same thesis was argued to apply to human beings by John B. Watson at around the same time.)
Thorndike meant to distinguish clearly whether or not cats escaping from puzzle boxes were using insight. Thorndike's instruments in answering this question were 'learning curves' revealed by plotting the time it took for an animal to escape the box each time it was in the box. 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's finding was that cats consistently showed gradual learning, which he took as support for his thesis that cats did not learn by miracle or even quickly, but by a gradual strengthening of an association between the situation and the response used to escape the box.