This study tests the following hypotheses: (a) the ability to solve disjunctive concepts increases with age; (b) positive instances are of greater use in solving conjunctive concepts while negative instances are of greater use in solving disjunctive concepts; (c) older children will show greater improvement than younger children in concept attainment performance as the proportion of negative instances increases in a disjunctive problem. The subjects were 36 second grade children and 36 fifth grade children. The stimuli consisted of 32 cards on which there were geometric forms varying on five binary dimensions. Subjects pointed out those cards in the array which they felt best met the examiner's verbal description. Results indicate that second and fifth grade children solved disjunctive and conjunctive concept attainment problems with either 20%, 50%, or 80% positive instances. The older children solved conjunctive concepts more easily than disjunctive concepts; both were equally difficult for the younger children. As the proportion of negative instances increased, disjunctive concepts were solved more easily. (Author/WY)