Effects of individualized incentives on norm-referenced IQ test performance of high school students in special education classes

The effects of student-specific material incentives on the norm-referenced IQ test performance of 485 high school students from 19 special education classes were examined. Students from a given special education class were randomly assigned to a control group (CG) or an incentive group (IG). Students in the CGs and IGs were retested using the same test, test level, and test form used to obtain their initial diagnostic IQ scores. The number of students in the CGs and IGs was 64 and 65 for the Otis-Lennon Mental Ability Test, 74 and 73 for the Lorge-Thorndike Intelligence Test, and 105 and 104 for the Wechsler Intelligence Scale for Children-Revised. The results show that the IG students, as compared with the CG students, obtained significantly higher verbal, performance, and full IQ scores and suggest that norm-referenced tests as diagnostic placement aides must be used with caution.