Three experiments were conducted to investigate the learning of the concept "more than" by preschool children. In the first experiment, 48 nursery school children, ages 4 1/2 to 5 1/2 years, were divided into three groups. All were required to say which of two pictures contained the greater number of objects. In group one, circles were used as the objects in the picture; for group two, like objects were used in each pair, but the types of objects varied between pairs; and in group three, unlike objects were used in the pictures. For each group, 42 trials were conducted per day for 3 days or to a criterion of eight consecutive correct responses. Subjects in groups one and two who reached criterion were given the same procedure again, except with unlike objects (a transfer condition). The results showed that subjects who initially learned the concept with the simplest stimuli (group one) learned most efficiently. Experiment two substantially replicated the results of experiment one, using children 41 to 51 months of age. Experiment three did likewise, using children with a mean age of 38 months. The overall results indicated that concept learning in young children was most efficient when the concept was introduced in the simplest context. (WD)