---
title: "Law of Effect — AP Psychology Definition & Exam Guide"
description: "Thorndike's Law of Effect says behaviors followed by satisfying outcomes get repeated. It's the foundation Skinner built operant conditioning on in AP Psych."
canonical: "https://fiveable.me/ap-psych-revised/key-terms/law-of-effect"
type: "key-term"
subject: "AP Psychology"
unit: "Unit 4"
---

# Law of Effect — AP Psychology Definition & Exam Guide

## Definition

The Law of Effect is Edward Thorndike's principle that behaviors followed by satisfying consequences become more likely to recur, while behaviors followed by discomfort become less likely. It is the foundational idea behind operant conditioning in AP Psychology.

## What It Is

The Law of Effect is Edward Thorndike's big idea from his famous puzzle box experiments. He put cats in boxes they could escape by pressing a lever or pulling a string. At first the cats flailed around randomly, but over many trials they escaped faster and faster. Thorndike's conclusion was simple and powerful. Responses followed by satisfaction get "stamped in" and become more likely when the situation repeats. Responses followed by discomfort get "stamped out" and fade.

In plain terms, consequences steer behavior. That one sentence is the seed of everything you learn about [operant conditioning](/ap-psych-revised/unit-3/8-operant-conditioning/study-guide/Xm5MTJSoAPDoVPrr "fv-autolink"). [B.F. Skinner](/ap-psych-revised/key-terms/bf-skinner "fv-autolink") took the Law of Effect and turned it into a full system, replacing vague words like "satisfaction" with measurable concepts like reinforcement and punishment. So when you see reinforcement schedules, shaping, or operant behavior on the exam, you're really seeing the Law of Effect in more precise clothing.

## Why It Matters

The Law of Effect lives in the learning topics of [AP Psychology](/ap-psych-revised "fv-autolink"), specifically Introduction to Learning (Topic 4.1) and Operant Conditioning (Topic 4.3). It matters because it marks the historical pivot from classical conditioning (Pavlov's reflexive, stimulus-triggered learning) to operant conditioning (voluntary behavior shaped by consequences). The exam expects you to know that Thorndike came first and Skinner built on him. If a question asks where the idea of [reinforcement](/ap-psych-revised/key-terms/reinforcement "fv-autolink") came from, the answer traces back to the Law of Effect. It's also your go-to concept whenever you need to explain why a behavior increases or decreases over time, whether the example is a rat in a Skinner box, a kid doing chores for allowance, or a student who stops raising their hand after getting laughed at.

## Connections

### B.F. Skinner (Topic 4.3)

Skinner took Thorndike's Law of Effect and made it scientific. Where Thorndike talked about "satisfaction" and "discomfort," Skinner measured response rates and defined reinforcement and [punishment](/ap-psych-revised/key-terms/punishment "fv-autolink") by their effect on behavior. Think of the Law of Effect as the rough draft and Skinner's operant conditioning as the published version.

### Punishment (Topic 4.3)

Punishment is the "discomfort weakens behavior" half of the Law of Effect. But here's the catch the exam loves. Punishment often suppresses behavior temporarily without teaching a replacement, so the Law of Effect alone can't fully explain long-term behavior change.

### Reinforcement Schedule (Topic 4.3)

[Reinforcement schedules](/ap-psych-revised/key-terms/reinforcement-schedules "fv-autolink") answer a question Thorndike never got to. The Law of Effect says satisfying consequences strengthen behavior, and schedules (fixed-ratio, variable-interval, etc.) tell you how the timing of those consequences changes how strong and persistent the behavior becomes.

### Conditioned Stimulus (Topic 4.1)

This is your classical-versus-operant boundary line. A [conditioned stimulus](/ap-psych-revised/key-terms/conditioned-stimulus "fv-autolink") triggers an automatic response before the behavior happens, while the Law of Effect is about consequences after a voluntary behavior. If the example involves what comes before the behavior, think Pavlov. If it's about what comes after, think Thorndike.

## On the AP Exam

The Law of Effect shows up almost entirely in multiple-choice questions, usually in one of three ways. First, straight identification, where a stem describes "behaviors followed by favorable consequences become more likely" and asks you to name the principle or its creator (Thorndike, not Skinner). Second, the Thorndike-Skinner relationship, asking how Skinner's research refined the Law of Effect into operant conditioning with measurable reinforcement. Third, application questions giving a scenario (a dog repeating a trick after treats, a worker slacking after a bonus is removed) and asking which principle explains it. Watch for limitation questions too, like why the Law of Effect struggles to explain long-term change through punishment alone. No released FRQ has used this term verbatim, but it's a clean concept to apply when an FRQ scenario asks you to explain why a behavior increased or decreased after a consequence.

## Law of Effect vs Operant Conditioning

These overlap so much that it's easy to treat them as the same thing, but the exam tests the difference. The Law of Effect is Thorndike's general principle that consequences shape behavior, discovered through his cat puzzle boxes. Operant conditioning is Skinner's expanded, systematic framework built on that principle, with precise terms like positive/negative reinforcement, punishment, shaping, and schedules. Quick rule: Law of Effect = the founding idea (Thorndike), operant conditioning = the full theory (Skinner).

## Key Takeaways

- The Law of Effect is Thorndike's principle that behaviors followed by satisfying consequences become more likely, and behaviors followed by discomfort become less likely.
- Thorndike discovered it using puzzle boxes, where cats learned to escape faster over repeated trials because escape (the satisfying outcome) strengthened the lever-pressing response.
- B.F. Skinner built operant conditioning on the Law of Effect, replacing vague terms like "satisfaction" with measurable concepts like reinforcement and punishment.
- The Law of Effect applies to voluntary behavior shaped by consequences, which separates it from classical conditioning, where a stimulus triggers an automatic response.
- A known limitation is that punishment under the Law of Effect may suppress a behavior temporarily without producing lasting change, since it doesn't teach a replacement behavior.
- On the exam, attribute the Law of Effect to Thorndike and operant conditioning to Skinner; mixing up the names is the classic trap answer.

## FAQs

### What is the Law of Effect in AP Psychology?

It's Edward Thorndike's principle that responses followed by satisfying consequences become more likely to recur, while responses followed by discomfort become weaker. It's covered in the learning topics (4.1 and 4.3) as the foundation of operant conditioning.

### Did Skinner come up with the Law of Effect?

No, Thorndike did, based on his cat puzzle box experiments. Skinner came later and refined the Law of Effect into operant conditioning, adding precise, measurable [concepts](/ap-psych-revised/unit-2/2-thinking-problem-solving-judgments-and-decision-making/study-guide/gHqqU9CdMYyy4lPn "fv-autolink") like reinforcement schedules and the Skinner box.

### How is the Law of Effect different from classical conditioning?

The Law of Effect deals with voluntary behavior and what happens after it (consequences strengthen or weaken the response). Classical conditioning, from Pavlov, deals with automatic responses triggered by a stimulus that comes before the behavior, like salivating at a bell.

### Is the Law of Effect the same as reinforcement?

Not exactly. The Law of Effect is the broad principle that consequences shape behavior, while reinforcement is Skinner's more specific term for any consequence that increases a behavior. Reinforcement is basically the modern, measurable version of Thorndike's "satisfaction."

### Is the Law of Effect on the AP Psych exam?

Yes, mainly in multiple-choice questions. Expect stems that describe consequences strengthening behavior and ask you to name the principle or Thorndike, or questions about how Skinner's operant conditioning refined Thorndike's original idea.

## Related Study Guides

- [4.3 Operant Conditioning](/ap-psych-revised/unit-4/operant-conditioning/study-guide/DUhup3HeqinYuyytGAJ4)
- [Unit 4 Overview: Learning](/ap-psych-revised/unit-4/review/study-guide/SSzKbswC0PjWeQ3FbTj0)

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