Learning occurs best when a person is mentally prepared.
Thorndike's third law, and the one that aged worst — it is closer to a statement about motivation than a testable regularity, and modern instructional design uses prerequisite knowledge instead.
In practice
- A trainee sent on the advanced course without the introductory one sits through three days and retains the coffee breaks.
- A class taught long division before it is secure with subtraction learns a procedure it has no way to check.