Contextual-Effects Models: Theoretical and Methodological Issues

Contextual-effects models represent an effort to explain individual-level de­ pendent variables using combinations of individualand group-level indepen­ dent variables. In the simplest models, the behavior Y ij of the ith individual in the jtb group is e�lain� by a combination of individual-level Xi/s and either the group mean Xj or Yj, representing the group average on the dependent variable. Joint effects may be additive or nonadditive, and there may be multiple contexts that are either nested or overlapping. Further complications involve ambiguities about self-selection into contexts, temporal sequences, and the causal ordering of individualand contextual-level variables, as well as about the diverse mechanisms through which contextual-level effects may operate. Any empirical analyses using contextual-effects models must presup­ pose both a causal model of such complex processes and the factual adequacy of a number of assumptions.