Abstract
Some cognitive psychologists, who have tried to approach psychometric theories, say that they do not provide them with theories and methods with which they can deal with different strategies. They are not exactly right. As early as in the late 1960's, the heterogeneous case of the graded response level in the context of latent trait theory was proposed as a model for cognitive processes. In the present paper a general trait model for different strategies in cognitive processes is proposed, and the maximum likelihood estimation of the individual's latent is discussed.