No. 302 · Your own mind · Heuristics and Bias
Observer-Expectancy Bias
We tend to see what we expect to see, and sometimes cause it without meaning to.
In the Almanac
“Clever Hans”, 1907 · “Deloitte UK”, 2015
Both stories in full, three ways to use it and where it misleads.
Get the AlmanacQuestions
What is Observer-Expectancy Bias?
Observer-Expectancy Bias is our tendency to perceive what we expect to perceive. Beliefs shape what we notice, what we overlook and even the subtle signals we send, which can nudge others toward the result we predicted.
How do you avoid Observer-Expectancy Bias?
To counter it, use blind methods: hide names when judging work, score before you know who made it, and set clear criteria in advance. Track concrete measures instead of impressions, and write down specific evidence before deciding someone is strong or weak.
When does Observer-Expectancy Bias matter?
Observer-Expectancy Bias is one of the 31 mental models for your own mind, the situations where you ask: Is my own thinking leading me astray? Within that, it belongs to “Seeing what you want to see”, alongside Blind Spot Bias, Cognitive Dissonance and Commitment and Consistency Bias.
What is an example of Observer-Expectancy Bias?
Two stories show it at work: Clever Hans (1907) and Deloitte UK (2015). Both are told in full in The Mental Models Daily Almanac, which has two stories for each of its 365 models.
Which mental models are related to Observer-Expectancy Bias?
Pygmalion Effect, Placebo Effect and Randomised Controlled Experiments. Observer-Expectancy Bias itself comes from heuristics and bias.