Attempted Solution to a Fundamental Psychobiological Problem How to Determine Individual and Milieu Parameters from Species-Typical Behaviour of Animals in Their Natural Environments

Sets out to find descriptive models for hierarchically organised behaviour using the relatively simple behavioural repertoire of the three-spined stickleback (Gasterosteus aculeatus L.) as a test case, but with potential generalisations to other species, including humans. In collaboration with statistician Georg Rasch, Reventlow arrived at determining quantitatively, for the first time in the study of behaviour, the relative effect upon a resulting, observed behaviour from the animal's sensitivity, motivation etc. (individual parameters) on the one hand, and those of the natural environment (milieu parameters) on the other.

Of special interest for the psychobiology of sticklebacks are his results concerning the motivational systems, that ethologists presume control two kinds of overt behaviour, as he presents experimentally based arguments for the existence of a third autonomous motivation-system for the male stickleback's building and maintenance of its nest which, together with the previously established two primary systems for mating and territorial defence, better explains the existing results than the ethologists' two-system's motivational hierarchy alone seems to be able to do.