FUNCTIONAL RELATIONSHIP BETWEEN AN OVERT RESPONSE AND ITS UNDERLYING MOTIVATION AS A BASIC REQUIREMENT FOR ETHOMETRY OF SIGN STIMULI

1. The strength RS of the mobbing response of the pied flycatcher (Ficedula hypoleuca) to avian predators increases by 44 calls/min following the hatching of its young (Fig. 2). The corresponding increase in mobbing motivation M is independent of the quality and the stimulus value of the models presented, rather it depends only on the readiness to mob which is a function of the stage of the breeding cycle. This permits the construction of a curve (Fig. 3) approximating the functional relationship RS=f(M). It is therefore possible to substitute the relative scaling of stimulus values with an absolute scale of motivational states, thereby establishing conditions for the quantitative evaluation of the law of heterogenous summation. 2. Changes in responsiveness are constant for all stimuli as for example in the pied flycatcher, a fish, and an insect. These changes could be factorial with respect to the original stimulus values as in some birds and fishes. 3. Mobbing movements and mobbing calls are induced by a common factor M to which the former respond at a lower threshold than the latter. This is based on observations of the time course of both mobbing elements, their dependence on RS, as well as the tendency to mobbing movements as a function of the tendency to call (Table). 4. The mobbing response exceeds the stimulation time sometimes up to 44 min and varies as a function of the RS to the presence of the enemy. Very weak responses evoke no after-reaction (Fig. 1). © 1969 Springer-Verlag.