Young, R. M., Bradley-Johnson, S., & Johnson, C. M. (1982). Immediate and delayed reinforcement on WISC-R performance for mentally retarded students . Applied Research in Mental Retardation , 3 (1), 13–20. https://doi.org/10.1016/0270-3092(82)90055-8

This study utilized three groups: control group, delayed reinforcement group, and immediate reinforcement group. The impact of positive reinforcement was examined.

Participants included 30 White children with intellectual disabilities, 19 boys and 11 girls. Their mean age was 10.5 years. All children came from families of low to middle socioeconomic status. Participants attended a school in the Mideast (U.S.).

Two tests were administered to each child: Slosson Intelligence Test (1963) to assess initial equality between the three groups, and the Wechsler Intelligence Scale for Children-Revised (WISC-R, 1974).

Both the immediate and delayed reinforcement groups showed significantly better performance than the standardized testing group, although the two reinforcement groups did not differ from one another. Half the children in each of the groups that earned tokens scored above the "mentally impaired" range while only one child in the standardized testing group scored above the "mentally impaired" range.