  Our stress relaxation measurements on wormlike micelles using a Rheo-SALS
(rheology + small angle light scattering) apparatus allow simultaneous
measurements of the stress and the scattered depolarised intensity. The latter
is sensitive to orientational ordering of the micelles. To determine the
presence of causal influences between the stress and the depolarised intensity
time series, we have used the technique of linear and nonlinear Granger
causality. We find there exists a feedback mechanism between the two time
series and that the orientational order has a stronger causal effect on the
stress than vice versa. We have also studied the phase space dynamics of the
stress and the depolarised intensity time series using the recently developed
technique of cross recurrence plots (CRPs). The presence of diagonal line
structures in the CRPs unambiguously proves that the two time series share
similar phase space dynamics.
