Facilitative effects of coin displacement on teaching coin summation to mentally retarded adolescents.

Two methods of teaching coin summation to retarded adolescents were compared: one method involved a coin-displacement procedure, the other did not. Displacement was designed to compensate for retarded persons' attention and retention deficits. A pretest-posttest matched-groups design as well as a multiple baseline across coin-counting responses were used. Fourteen retarded subjects were assigned to either displacement or nondisplacement conditions. Subjects in both groups were first taught to count a single coin and then sum that coin in combination with coins previously taught. Both groups used the same finger-counting procedure; however, subjects in the displacement condition were also required to move each coin aside systematically after it was counted. The training methods were modeling, modeling with subject imitation, and independent counting by the subject. Both groups improved from pre- to posttest; however, the displacement group performance was significantly better. Skill maintenance for both groups was evident on follow-up. Displacement subjects required fewer trials and less time to complete training. Coin displacement may compensate for attention and retention deficits of retarded persons.