Increasing the Work Rates of Visually-Impaired, Mentally Retarded Adults through the Treatment and Prevention of Overselectivity (Overshadowing) and Masking

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Schwade, John
thesis / dissertation description
In Experiment 1, three legally-blind, mentally retarded adults were given 10 to 12 applications of discrimination training between pairs of sequential compound stimuli with immediate tactile and delayed (3- 3.5 sec) visual elements. Sorting responses were brought under the control of these stimuli. In 29 of 33 applications, discrimination training resulted in reduced sorting rates concommittant to overselectivity (overshadowing), such that stimulus control was acquired by only delayed visual elements. Single-stimulus discrimination training (SSDT) between the previously-overshadowed immediate tactile elements produced expression of stimulus control by those elements of compound stimuli in 5 of 6 cases. SSDT with novel stimuli produced expression of stimulus control by immediate tactile elements of compound stimuli in 6 of 6 cases. In Experiment 2, three cases of masking, where stimulus control acquired by tactile elements in Experiment 1 was not expressed when tactile elements were presented in compound stimuli, were successfully treated by differential reinforcement of correct sorting responses occurring before the presentation of the delayed visual element.