If we have a bad causal theory that A causes B, we will notice only examples of A's that are B's. Bias is both in noticing and in seeking more information. This bias exists in memory. Tendency for people to find whatever is presented as evidence for their own position. Cold cognition as well as hot.
Beliefs tend to perservere once in existence.
We never get to observe what would have happened if we had acted differently. Do well Do poorly High grades Low grades E.g. free trade unemployment up unemployment down free trade no free trade no information available no information available Self-fulfilling prophecies. E.g. identifying certain students as smart. Special case of hidden data phenomena Turn little effects into big effects, e.g. despondent student not studying. Correlation A and B tend to occur together.