One-liner: New information will strengthen beliefs you already have.
Example: Two opposing groups. Two fabricated texts strengthening each group's ideas. Both groups read both texts. Both groups come out of this exercise believing more what they believed prior via Biased assimilation and attitude polarization Cited in:
So for example, in 1979 some psychologists asked partisans to read pairs of studies about capital punishment (a controversial issue at the time), then asked them to rate the methodologies on a scale from -8 to 8. Conservatives rated the pro-punishment study at about +2 and the anti-execution study as about -2; liberals gave an only slightly smaller difference the opposite direction. Of course, the psychologists had designed the studies to be about equally good, and even switched the conclusion of each study from subject to subject to average out any remaining real difference in study quality. At the end of reading the two studies, both the liberal and conservative groups reported believing that the evidence had confirmed their position, and described themselves as more certain than before that they were right. The more information they got on the details of the studies, the stronger their belief.
- Pattern Recognition. You are more likely to find what you already are looking for.
- Ego. I am incentivized to find confirming information to protect my ego.
- Groupthink. In case of controversial topics, you will be punished if you break from your group thinking.
Observer-expectancy is a similar effect. If you are looking for something to happen you might invent it out of a thin air (especially applying to scientific research and
It explains why people are more likely to vote how their parents voted
Belief bias