A researcher's expectations leak into procedure, prompting and scoring, and move the result.
Rosenthal's 1963 demonstration used rats labelled "maze-bright" and "maze-dull" at random, and the labelled-bright rats performed better. Blinding exists because of this result.
In practice
- An interviewer who rates a candidate highly asks easier follow-ups and scores the answers generously, without noticing either.
- A trial assessor who knows which arm the patient is in records ambiguous symptoms differently, which is why allocation is concealed.
- Standing
- The reason blinding exists. The classroom version is the Pygmalion effect, listed separately.
- Subject
- Science & Epistemology
- Essay
- The ways evidence misleads