Psychology Reader

In Defense of External Invalidity

Douglas G. Mook · 1983 · American Psychologist

Role
Foundational argument · Critical reappraisal
Difficulty
Moderate
Full work length
9 pages
Type
Journal article

Access

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Reading focus

Syllabus: When Do Psychological Findings Generalize?

Set Mook’s distinction beside the scope statement. A deliberately unusual condition may be useful if a theory makes a clear prediction about it.

Why you’re reading it. Distinguish testing a mechanism from estimating how often a pattern occurs in everyday life.

A question to consider. How would your evaluation of the memory experiment change if its purpose were to challenge a theory rather than recommend a classroom practice?

Why this reading

Mook asks what an experiment is trying to accomplish before judging whether its setting resembles everyday life. His distinction between testing an explanation and estimating a real-world pattern changes how apparently artificial research should be evaluated.

Before you read

Internal validity concerns a causal interpretation within a study. External validity concerns extending an inference beyond it. Mook uses external validity particularly for moving findings from the laboratory to everyday settings; later authors sometimes use the term more broadly.

Read for

  1. Distinguish showing that something can occur, testing a prediction and estimating what usually occurs.
  2. Examine the assumptions connecting each historical example to the theoretical conclusion Mook draws.

Consider afterwards

  1. A tightly controlled task challenges a proposed memory mechanism. What would make it a fair test of that mechanism, and what further evidence would be needed before advising teachers?

Editorial context

This 1983 argument does not establish the present evidential status of every historical example it discusses. Its defense of artificiality does not excuse weak operationalization, unsupported population claims or ethical problems. The adequacy of a theoretical test still needs a substantive argument.