Here is a VRML version of Lorenz' model. This requires a VRML plug-in which is installed on computers in Psychology department. Animals reared in isolation will show aggressive behaviour. According to Lorenz's theory the degree of consummatory response is a function of the amount of accumulated action specific energy and the sign stimuli to which the animal is exposed. Baerends and his colleagues have provided an elegant demonstration of this principle.
Male guppies exhibit several patterns of courtship behaviour.
The external markings of a male guppy vary with its readiness to show courtship. In terms of Lorenz's model, the external markings are an indication of the level of action specific energy for courtship. The sign stimulus value of the female increases with her size. Baerends conducted experiments in which males with different external markings were exposed to females of various sizes. The results of these tests are shown below and indicate that for each pattern of male courtship behaviour, the size of the female needed to elicit the pattern was less the greater the readiness of the male to court.