Interrater reliability of the Motivation Assessment Scale: failure to replicate with aggressive behavior.

The Motivation Assessment Scale (MAS) was used to identify the variables maintaining aggressive behaviors exhibited by 18 adolescents and adults with severe to profound intellectual disability. Each client was rated by two staff members. A variety of measures were calculated to assess interrater reliability. Pearson coefficients across the 18 pairs of raters ranged from -.667 to .722 with an overall correlation of .034. Five of the 12 positive correlations were significant at the .05 level. Correlations across each of the 16 questions of the MAS ranged from -.337 to .425. None of these correlations were significant. Similarly low reliability was obtained when percentage of agreement measures were calculated, although 8 of the 18 pairs of raters (44.44%) did agree on the source of reinforcement maintaining the client's aggressive behavior. These results suggest that for some individuals the MAS may not represent a viable alternative to more formal functional analysis procedures.