Effects of within-stimulus and extra-stimulus prompting of letter discrimination by mentally retarded persons.

Two different prompting procedures for teaching letter discrimination to mentally retarded persons were compared. Each of 24 severely retarded subjects received training on six alphabet letters, three by extra-stimulus prompting (adding to topographically different cue, a pointing finger) and three by within-stimulus prompting (accentuating critical features of the stimuli themselves). Letter discrimination was tested prior to, immediately following, and 2 weeks after training. A significantly greater proportion of letters trained by within-stimulus prompting was learned (p less than .001), thereby replicating past research with autistic children. Since mentally retarded persons are overselective and attend to few cues in a stimulus array, within-stimulus prompting may be more effective than between-stimulus prompting.