Participant skepticism: If you can't beat it, model it

For a variety of reasons, including the common use of deception in psycholo gy experiments, participants often disbelieve experimenters' assertions abo ut important task parameters. This can lead researchers to conclude incorre ctly that participants are behaving non-normatively. The problem can he ove rcome by deriving and testing normative models that do not assume full beli ef in key task parameters. A real experimental example is discussed.