To test the theory that retardates are particularly slow in forming some visual habits, especially attention, a series of experiments were performed using a laboratory device which forced subjects to discriminate between color and form in exchange for an incentive reward. Stochastic models were applied to tests of lower level retardates which measured original learning reversals, effects of intelligence, stimulus factors, reward schedule, and transfer operations. It was found that retardates have difficulty attending to the relevant stimulus. Theoretical background, test procedures, results, and conclusions are described in detail. (EMH)