We compared the predictability of the behaviour of hyperactive children with that of aggressive children, combined hyperactive/aggressive children and normal children. Detailed behaviour measurements relating to each child and an experimenter were recorded during playroom session. Predictability was expressed in information-theoretical measures and data were tested by means of a Multivariate Analysis of Variance (MANOVA) with between-subject factors "hyperactivity" and "aggression". Hyperactivity was characterised by chaotic social and communicative interaction between child and experimenter and by rigidity in the intra-child transitions of activity states. Aggression on the other hand, was associated with lower predictability of activity behaviours of the child in the context of interaction with the experimenter, which may be due to oppositional features in the child.
