The Wisdom of Many in One Mind

Averaging many people’s estimates of, e.g., when a famous event occurred tend to be better than asking any one arbitrary person.   Herzog and Hertwig (2009) investigated whether the average of two estimates from one person tended to be better than their first estimate, using the years of 40 historical events, e.g., when electricity was invented.

There were three conditions:

  1. Repeated sampling: just giving an estimate twice.
  2. So-called “dialectical” sampling (they cite Hegel here), where participants were told: “First, assume that your first estimate is off the mark. Second, think about a few reasons why that could be. Which assumptions and considerations could have been wrong? Third, what do these new considerations imply? Was the first estimate rather too high or too low? Fourth, based on this new perspective, make a second, alternative estimate.”
  3. Pairing each participant’s guess with a random other participant.

Results are below:


The instruction to consider you were wrong increases accuracy beyond that with simple repeated measurement.  Best of all is averaging with another person.


Herzog, S. M. & Hertwig, R. (2009). The Wisdom of Many in One Mind: Improving Individual Judgments With Dialectical Bootstrapping. Psychological Science, 20, 231-237