The Scientific Method: Learn It 2—Theories and Hypotheses

Theories and Hypotheses

Two key concepts in the scientific approach are theory and hypothesis.

What Is a Theory?

theory

A theory is a well-developed set of ideas that explains observed phenomena and allows researchers to make predictions about future observations.

  • For example, the theory of evolution by natural selection explains how genetic traits change over generations.

  • In psychology, theories help explain how children develop, how people behave in social situations, and why we experience particular emotions.

Theories are not guesses—they are comprehensive frameworks supported by evidence that guide scientific inquiry and prediction.

hypothesis

A hypothesis is a testable prediction logically derived from a theory or observation. Testing hypotheses allows scientists to refine or modify theories based on evidence.

  • A hypothesis is often phrased as an if–then statement.

    • Example: If I study all night, then I will earn a passing grade on the test.

The results of a study will either support or challenge the theory. When results do not align, researchers modify the theory and generate new hypotheses.

 

A diagram has seven labeled boxes with arrows to show the progression in the flow chart. The chart starts at “Theory” and moves to “Generate hypothesis,” “Collect data,” “Analyze data,” and “Summarize data and report findings.” There are two arrows coming from “Summarize data and report findings” to show two options. The first arrow points to “Confirm theory.” The second arrow points to “Modify theory,” which has an arrow that points back to “Generate hypothesis.”
Figure 1. The scientific method involves deriving hypotheses from theories and then testing those hypotheses. If the results are consistent with the theory, then the theory is supported. If the results are not consistent, then the theory should be modified and new hypotheses will be generated.

Example: The James-Lange Theory of Emotion

To see this process in action, let’s consider a classic psychological theory.

- James lange theory of emotion flowchart showing that arousal (like from a snake) leads to the heart pounding and sweating, which leads to the emotion of fear.
Figure 2. The James-Lange Theory proposes that emotional responses come after the physical experience.

The James-Lange theory of emotion proposes that emotional experience depends on physiological arousal—that is, our body’s physical reactions occur first, and emotions follow.

Northern copperhead snake
Figure 3. According to the James Lange theory of emotion, a person who is unable to experience the physical symptoms of being startled by a snake, like a racing heartbeat, would not experience the emotion of fear.

For example, imagine walking outside and finding a snake on your doorstep. Your heart races, your stomach tightens—and then you feel fear.

From this theory, we might form the hypothesis:

People who are unaware of their physiological arousal will not experience fear.

Researchers tested this idea by studying individuals with severe spinal cord injuries who cannot feel typical bodily changes. Results showed that although these individuals’ emotional experiences were less intense, they still felt emotions such as fear (Chwalisz, Diener, & Gallagher, 1988).

This evidence did not fully support the hypothesis, prompting refinements to the theory.