Two normal and two mentally retarded children were trained to earn pennies by pressing a key according to a multiple variable-interval extinction schedule of reinforcement. Retarded children differed from normal children by producing more positive than negative discriminative stimuli. (Author/DB)

This study measured the differential effects of simplified and typical verbal antecedents on acquisition of picture discriminations for four preschool children with autism. During baseline probes, participants emitted no correct selection responses to pictures of common stimuli during either simplified or typical verbal antecedent conditions.…