At a high level, probabilities can be incorporated into a computational cognitive model in two different, not mutually exclusive, ways. First, representations in the cognitive system can include or employ probabilities, where the authors take a very broad view of the notion of "representation". Second, probabilities can be used in a computational cognitive model to capture noise and indeterminism in the cognitive agent. This chapter talks about computational cognitive models as though they apply to particular individuals; that is, cognitive models were discussed in the context of explaining the cognitive processes of particular individuals. Probabilistic cognitive models will generally not predict any specific behavior at all, but rather a range and likelihood of possible behaviors. In the case of probabilistic cognitive models, almost any behavior will be predicted to be possible, though the model might predict that this behavior should be unlikely or rare.