  We propose a belief-formation model where agents attempt to discriminate
between two theories, and where the asymmetry in strength between confirming
and disconfirming evidence tilts beliefs in favor of theories that generate
strong (and possibly rare) confirming evidence and weak (and frequent)
disconfirming evidence. In our model, limitations on information processing
provide incentives to censor weak evidence, with the consequence that for some
discrimination problems, evidence may become mostly one-sided, independently of
the true underlying theory. Sophisticated agents who know the characteristics
of the censored data-generating process are not lured by this accumulation of
``evidence'', but less sophisticated ones end up with biased beliefs.
