Falsification

Overview

Karl Popper (Logik der Forschung, 1934): a claim earns credibility only from surviving attempts to refute it — confirming instances are cheap and unbounded. Wason's 2-4-6 experiment (1960) showed the default human strategy: given a rule to discover, people propose only sequences their hypothesis says are valid, receive "yes" after "yes", and announce the wrong rule with confidence. They never propose a sequence their hypothesis says should FAIL.

The blind spot: a green test you designed to pass tells you almost nothing. The information is in the test designed to fail.

When to Use

• Verifying a bug fix ("it works now")
• Any hypothesis about system behavior, user behavior, or root cause
• Writing tests for new code
• A validation process that has never rejected anything

The Procedure