Effects of antipsychotic medication on discrimination learning for institutionalized adults who have mental retardation

Reduction in medication levels of drugs used to suppress inappropriate behavior (chlorpromazine, thioridazine and haloperidol) resulted in increases in performance on a discrimination learning task for seven residents of a state institution who are mentally retarded. After training to criterion on a matching‐to‐sample task, these participants experienced reductions in medication in an N of 1 AB replication paradigm. Two controls were medication free, and one remained on a stable dosage throughout. Improvement of performance on the first dependent variable (number of trials needed to meet criterion) ranged from 13.8% to 53.3% for the seven participants, while the three controls improved less than 1%. Improvement of performance on the second dependent variable (percentage of correct responses) ranged from 2.7% to 19.7% for experimental subjects; five of the seven subjects exhibited a minimum improvement of 8%. The change in percentage of correct responses for the three controls ranged from −4.9 to 1.3. Treatment implications are discussed.