PSYCHOTHERAPY AS A CHAOTIC PROCESS .2. THE APPLICATION OF NONLINEAR-ANALYSIS METHODS ON QUASI TIME-SERIES OF THE CLIENT-THERAPIST INTERACTION - A NONSTATIONARY APPROACH

Quasi time series obtained by the method of ''Sequential Plan Analysis '' are analyzed. These time series represent the dynamics of behavior exhibited by a client and therapist during 13 sessions of solution-ori ented psychotherapy. Nonlinear methods assume that dynamic attractors remain stable during the measurement of the investigated process. This stationarity assumption may not be justified between and within thera py sessions. It may be more realistic to expect dynamical changes in t he form of phase-transition-like phenomena during the therapeutic proc ess. Here, we applied to our data measures which do not assume station arity of the underlying dynamics. These measures (the pointwise PD2 al gorithm, entropy rates, and chaoticity measure based on local Lyapunov Exponents) are explained. The results, especially those obtained from calculation of local Lyapunov Exponents, suggested that critical tran sitions occur within the therapeutic process. The implications and con sequences for theory, research, and the practice of psychotherapy are outlined.