Cobra Effect · Thinking and evidence
The halo effect
One good quality colours how we judge all the others.
6 cards, read aloud in 2:33, with a test and sources.
1920. An army officer sits down to rate his men.
Physique. Intelligence. Leadership. Character. Separate qualities, separate boxes. The psychologist Edward Thorndike collects the forms and notices something odd. The tall, handsome soldiers are also, apparently, the clever and loyal ones.
The ratings agree with each other too well.
Thorndike called his paper A Constant Error in Psychological Ratings. A man rated high on bearing was rated high on everything. The officers were not judging four things. They were judging one thing, then colouring the rest to match.
That is the halo effect.
One trait you notice first, usually looks, warmth or success, spreads over everything else you judge. The halo in the name is the glow around a saint’s head in old paintings. It works in the dark too. One bad trait dims the rest.
1977. The same lecturer, twice.
Richard Nisbett and Timothy Wilson filmed a lecturer with a strong accent answering questions. In one version he was warm and friendly. In the other, cold and stiff. Students who saw the warm version found his accent charming and his manner attractive. Students who saw the cold version found the same accent irritating. Asked whether liking him had affected their ratings, the students said no.
The halo runs whole companies.
Phil Rosenzweig showed in 2007 how business books fall for it. When a firm’s profits rise, journalists describe its culture as bold and its leader as visionary. When profits fall, the same culture is reckless and the same leader is arrogant. Nothing inside the firm changed. The share price did, and the halo followed it.
Judge one thing at a time, and blind if you can.
Rate each quality before you look at the next. Hide the things that glow. The name, the school, the last result, the face. A good interview scores each answer before the next question is asked. When someone is impressive, ask which single thing impressed you. Then ask what else you actually know.
Sources
- Halo effect, Wikipedia. Thorndike’s 1920 paper with the army ratings, the Nisbett and Wilson lecturer study of 1977, and the long list of things a halo has been shown to spread from.
- The Halo Effect, Phil Rosenzweig, 2007. How business books read a company’s culture and leadership off its share price, and why the lessons of the famous management bestsellers do not survive the next bad year.
- Edward Thorndike, Wikipedia. The psychologist behind the 1920 paper, better known for his work on learning in animals and children. Search A Constant Error in Psychological Ratings for the paper itself.
Nearby ideas
- The fundamental attribution error. We blame people’s character and overlook their situation.
- The narrative fallacy. We invent causes for events because stories feel like explanations.
- Outcome bias. Judge a decision by what was known, not by how the dice fell.
- Motivated reasoning. We set a lower bar for evidence we want to believe.
- The Texas sharpshooter fallacy. Draw the target after the shots and any pattern looks meaningful.
- The Semmelweis reflex. Why experts reject evidence that says they have done harm.
- The illusion of explanatory depth. We think we know how things work until we try to explain them.
- Gell-Mann amnesia. We spot the errors in our own field, then trust everything else.