---
title: "Weber's Law — AP Psychology Definition & Exam Guide"
description: "Weber's Law says the just noticeable difference is a constant proportion of the original stimulus. Learn the formula, examples, and how AP Psych tests it."
canonical: "https://fiveable.me/ap-psych-revised/key-terms/webers-law"
type: "key-term"
subject: "AP Psychology"
---

# Weber's Law — AP Psychology Definition & Exam Guide

## Definition

A principle describing the relationship between stimulus and resulting sensation, stating that the Just Noticeable Difference is a constant proportion of the original intensity of the stimulus.

## Related Study Guides

- [3.1 Principles of Sensation](/ap-psych-revised/unit-3/principles-sensation/study-guide/9G8CkjXjhzo9PSEgGtqZ)

## Review

### Related Terms

- [Psychophysics](/ap-psych-revised/key-terms/psychophysics): The study of relationships between physical stimuli and mental phenomena.
- Fechner's Law: It states that perceived intensity increases as a logarithm to actual physical intensity.
- Stevens' Power Law: An empirical relationship in psychophysics between an increased level of physical stimulus and perceived intensity.