The confidence effect refers to boosts in confidence of individuals after the convergence of estimates within the group, despite there being no actual improvement in response accuracy. 

Syracuse University

The wisdom of crowd effect suggests that the median estimate of a group is more likely to have  closer accuracy to an answer than the estimate of an individual.

Wisdom of Crowd Effect

Social influence reduces diversity in crowd responses which diminishes the accuracy of the group median estimate.

The Social Influence Effect in Relation to Crowd Estimates


Lorenz, J., Rauhut, H., Schweitzer, F., &amp; Helbing, D. (2011). How social influence can undermine the wisdom of crowd effect. Proceedings of the National Academy of Sciences, 108(22), 9020–9025. https://doi.org/10.1073/pnas.1008636108  

How social influence can undermine the wisdom of crowd effect

The range reduction effect refers to the phenomenon of when the position of truth for a group estimate moves to the peripheral regions of the range of estimates. This makes the crowd’s estimated response less reliable.

Range Reduction Effect

Confidence Effect in Reference to Group Estimates

Average individual error - group’s diversity = collective error

Diversity Prediction Theorem

- Suspect that others have better information
- Peer pressure to conform
- Group deliberation of facts


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