2.2.5—Confirmation bias
- Syllabus
- First assessment 2027
- Objective
- 2.2.5
- Level
- SL
Confirmation bias protects a preferred belief from disconfirming evidence
Confirmation bias is the tendency to seek, interpret or remember information in ways that support an existing belief while discounting conflicting evidence.
It can operate through search, attention, interpretation and memory. Strong prior commitment, identity relevance and ambiguous evidence can increase it; preregistered tests and deliberate consideration of alternatives can reduce it.
A researcher expecting a treatment to work may notice supportive cases first and explain away null results. A blind analysis and explicit stopping rule make that mechanism harder to operate.
Disagreement is not automatically confirmation bias. Identify the prior belief and the systematic way evidence is being filtered.