Combining dynamic systems and multivariate analyses to compare the mother-child interactions of externalizing subtypes.

A dynamic systems analysis was conducted to distinguish the parent-child interactions of "pure" externalizing children from children comorbid for externalizing and internalizing problems. Thirty-three parents and clinically referred children (8-12 years old) discussed a problem for 4 min and then tried to "wrap up" in response to a signal (a perturbation). The perturbation was intended to increase the pressure on the dyad, triggering a reorganization of their behavioral system. We hypothesized that the comorbid group would be distinguished from the externalizing-only group as a result of this reorganization, but not before. The sequential data were analyzed using a combination of case-sensitive (state space grids and chi-square analyses) and group-based, multivariate techniques (log-linear modeling). Results revealed that externalizing dyads engaged in a permissive pattern throughout the problem-solving session, whereas comorbid dyads shifted from a permissive pattern to a mutually hostile pattern after the perturbation. These findings punctuate the need for a dynamic systems approach to the study of relationship processes associated with the development of childhood psychopathology. Theoretical and clinical implications are discussed.