What is the law of exercise?

Edward L. Thorndike, answered from the texts and cited to the page.

Edward L. Thorndike answers

The Law of Exercise is the name I give to the pair of tendencies — use and disuse — that govern whether a connection between a situation and a response grows stronger or weaker over time. The Law of Use states that when a modifiable connection between a situation S and a response R is made, that connection's strength is, other things being equal, increased.¹

By strength I mean roughly the probability that the connection will be made when the situation recurs — a greater probability for the same span of time, or an equal probability sustained for a longer span.² To think "6+7=13" attentively and for ten seconds will increase the strength of that bond more than to think of it lightly and for only half a second; vigor and duration of the making matter, not frequency alone.³

The Law of Disuse is the complement: when a modifiable connection between S and R is not made during a length of time T, man responds, other things being equal, by a decrease in the strength of that connection.⁴ These two tendencies I list together under the single name, the Law of Exercise.⁵ But exercise alone does not tell the whole story of learning, which is why the Law of Effect must stand beside it — the strengthening or weakening of a connection according to whether a satisfying or annoying state of affairs accompanies or follows it.⁶

The two laws together, exercise and effect, are the effective original forces in what has variously been called nurture, training, learning by experience, or intelligence itself.⁷

Sources

1. The Law of Use is: When a modifiable connection is made between a situation and a response, that connection's strength is, other things being equal, increased.

   Educational Psychology Vol 2 The Psychology of Learning

2. By the strength of a connection is meant roughly the probability that the connection will be made when the situation recurs. Greater probability that a connection will be made means a greater probability for the same time, or an equal probability, but for a longer time.

   Educational Psychology Vol 2 The Psychology of Learning

3. To think '6+7=13' attentively and for ten seconds will thus increase the strength of its bond more than to think of it lightly and for only half a second.

   Educational Psychology Vol 1 The Original Nature of Man

4. To the situation, 'a modifiable connection not being made by him between a situation S and a response R, during a length of time T,' man responds originally, other things being equal, by a decrease in the strength of that connection.

   Educational Psychology Briefer Course

5. The tendencies of use and disuse may be listed together under one name as the Law of Exercise.

   Educational Psychology Briefer Course

6. To the situation, 'a modifiable connection being made by him between an S and an R and being accompanied or followed by a satisfying state of affairs' man responds, other things being equal, by an increase in the strength of that connection. To a connection similar, save that an annoying state of affairs goes with or follows it, man responds, other things being equal, by a decrease in the strength of the connection.

   Educational Psychology Briefer Course

7. These tendencies for connections to grow strong by exercise and satisfying consequences and to grow weak by disuse and annoying consequences should, if importance were the measure of the space to be allotted to topics, preempt at least half of this inventory. They are the effective original forces in what has variously been called nurture, training, learning by experience, or intelligence.

   Educational Psychology Briefer Course