Pluralistic ignorance
Pluralistic ignorance can be contrasted with the false consensus effect. In pluralistic ignorance, people privately disdain but publicly support a norm (or a belief), while the false consensus effect causes people to wrongly assume that most people think like they do, while in reality most people do not think like they do (and express the disagreement openly). For instance, pluralistic ignorance may lead a student to drink alcohol excessively because she believes that everyone else does that, while in reality everyone else also wishes they could avoid binge drinking, but no one expresses that due to the fear of being ostracized. A false consensus for the same situation would mean that the student believes that most other people do not enjoy excessive drinking, while in fact most other people do enjoy that and openly express their opinion about it.
Knightian uncertainty
The Ellsberg paradox is based on the difference between these two types of imperfect knowledge, and the problems it poses for utility theory – one is faced with an urn that contains 30 red balls and 60 balls that are either all yellow or all black, and one then draws a ball from the urn. This poses both "uncertainty" – whether the non-red balls are all yellow or all black – and "probability" – whether the ball is red or non-red, which is ⅓ vs. ⅔. Expressed preferences in choices faced with this situation reveal that people do not treat these types of imperfect knowledge the same. This difference in treatment is also termed "ambiguity aversion".