AP® Psychology · Unit 3 · Topic 3.8
The Law of Effect
The law of effect says behaviors followed by satisfying consequences get repeated, and behaviors followed by unpleasant ones fade out, with no understanding required at all.
Edward Thorndike put cats in puzzle boxes they could only escape by pressing a lever or pulling a loop. The first time, a cat flails around and stumbles onto the lever by accident. Escape follows. Next trial, that same accidental swipe happens a little sooner, because it was followed by something satisfying. Over many trials the useless flailing drops away and the lever-press gets faster and more direct. Thorndike called this the law of effect: behaviors followed by satisfying consequences become more likely to recur, and behaviors followed by annoying or unhelpful consequences become less likely to recur. Nothing about insight or reasoning is required. The cat never figures out how the latch works. The consequence just quietly edits the odds of each behavior happening again.
This is trial-and-error learning, and it is the seed that grew into operant conditioning. B.F. Skinner later built a whole system of reinforcement and punishment on exactly this principle, formalizing what counts as a consequence and how schedules of consequences shape behavior over time. But the core idea stays Thorndike's: consequences select behavior the way natural selection selects traits — not by teaching understanding, just by making some actions survive and others disappear from the organism's repertoire.
The law of effect is easy to confuse with classical conditioning because both involve learning through experience, but they work on completely different targets. Classical conditioning rewires an involuntary reflex by pairing it with a new stimulus — salivating to a bell instead of just to food. The law of effect strengthens or weakens a voluntary action based on what happens after the animal does it. Stimulus-response pairing versus behavior-consequence pairing: that is the real dividing line.
Key terms
- Law of effect
- Behaviors followed by satisfying consequences are strengthened; behaviors followed by unsatisfying consequences are weakened.
- Puzzle box
- Thorndike's experimental box that an animal could escape only by performing a specific action, like pressing a lever.
- Trial-and-error learning
- Gradually improving performance by repeating accidental successes and dropping unsuccessful actions, without understanding why.
- Operant conditioning
- Learning in which voluntary behavior is shaped by the consequences that follow it, built on the law of effect.
- Classical conditioning
- Learning in which a neutral stimulus comes to trigger an involuntary reflex response through repeated pairing.
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End of topic.