Temporal patterns of human behaviour: are there signs of deterministic 1/fscaling?

Temporal patterns apparently exhibiting scaling properties may originate ei ther from fractal stochastic processes or from causal (i.e., deterministic) dynamics. In general, the distinction between the possible two origins rem ains a non-trivial task. This holds especially for the interpretation of pr operties derived from temporal patterns of various types of human behaviour , which were reported repeatedly, We propose hero a computational scheme ba sed on a generic intermittency model to test predictability (thus determini sm) of a part of a time series with knowledge gathered from another part. T he method is applied onto psychodynamic time series related to turns from n on-psychosis to psychosis. A nonrandom correlation (rho = 0.76) between pre diction and real outcome is found. Our scheme thus provides a particular ki nd of fractal risk-assessment for this possibly deterministic process. We b riefly discuss possible implications of these findings to evaluate the risk to undergo a state transition, in our case a patients risk to enter a next psychotic state. We further point to some problems concerning data sample pecularities and equivalence between data and model setup, (C) 2000 Elsevie r Science B.V. All rights reserved.