BiasBelief updating · Belief Perseverance · Entry 2
Conservatism Bias – when new evidence doesn't change old beliefs
You receive new information, but it barely changes your opinion? That’s Conservatism Bias – the tendency to insufficiently revise one's beliefs even when presented with new evidence.
Where it can show up
- Finance – you hold onto a stock despite news that the company is struggling.
- Science – new research disproves old theories, but you find it hard to accept the change.
- Personal life – someone has changed, but you still judge them by their past actions.
A practical countermeasure
- Double-check facts – new isn’t always better, but ignoring updates is risky.
- Question old beliefs – the world evolves, maybe your views should too.
- Stay flexible – adapting to new data makes you smarter and better at decision-making.
Evidence review
established in belief-updating tasksWhat the evidence supports
Here, conservatism means under-updating: new evidence changes a probability judgment less than a Bayesian benchmark would predict. It should not be confused with the separate memory phenomenon in this corpus that pulls remembered extreme values toward the middle.
How researchers describe the pattern
In probability-updating tasks, people can place too much weight on a prior belief relative to new diagnostic information. Different models explain this pattern in different ways, so the observed under-update is firmer than any single mechanism proposed to explain it.
Practical interpretation
When new evidence matters, write down the prior estimate, the new evidence, and the updated estimate separately. This makes it easier to notice when the answer barely moved simply because the original belief felt familiar. Treat this as a decision procedure, not a guaranteed debiasing cure.
Reviewed sources
- The neural basis of belief updating and rational decision making experiment · 2014 · DOI 10.1093/scan/nss099
- Surprisingly rational: probability theory plus noise explains biases in judgment model + experiments · 2014
Editorial review: 2026-08-18. Evidence status describes this entry, not every study ever published on the topic.
