Instrumental and expressive representations of aggression: One scale or two?

The Expagg questionnaire was developed to measure a subject's view of their own aggression as a relatively instrumental or relatively expressive act. Two issues have been raised pertaining to the dimensional structure of the questionnaire: the use of principal components analysis on dichotomous resp onses and the possibility that instrumental and expressive representations might be independent dimensions rather than opposite ends of a single conti nuum. In study 1, dichotomous Expagg data from 405 subjects were subjected to microfact, principal components, and factor analysis. Each produced a fi rst general factor, and the correlations between the item loadings were in excess of r = .99. In study 2, a 40-item Likert scale version of Expagg was given to 295 subjects. Principal components analysis, paired item correlat ions, and subscale correlations suggested partial independence of instrumen tal and expressive items. Two new 8-item scales measuring instrumental and expressive representations were constructed that maximise their independenc e. Potential. uses of these revised scales are discussed. (C) 1999 Wiley-Li ss, Inc.