This bias describes human belief revision in which people over-weigh the prior distribution (base rate) and under-weigh new sample evidence when compared to Bayesian belief-revision.
According to the theory, "opinion change is very orderly, and usually proportional to the numbers of Bayes' theorem – but it is insufficient in amount".
Edwards suggested that people updated beliefs conservatively, in accordance with Bayes' theorem, but more slowly.
[1] In finance, evidence has been found that investors under-react to corporate events, consistent with conservatism.
[2] The traditional explanation for this effect is that it is an extension of the anchoring bias, as studied by Tversky and Kahneman.
The initial "anchor" is the .5 probability given when there are two choices without any other evidence, and people fail to adjust sufficiently far away.
Alternatively, one study suggested that the belief revising conservatism can be explained by an information-theoretic generative mechanism that assumes a noisy conversion of objective evidence (observation) into subjective estimates (judgement).
In an incentivized experimental study, it has been shown that the conservatism bias decreased in those with greater cognitive ability, though it did not disappear.