Use of tools by wild macaque monkeys in Singapore.

Abstract

IN 1940 Tinbergen1 and Kortlandt2 independently drew attention to a behavioural phenomenon which has since been called displacement activity and has received a good deal of attention3,4. Although no binding rules exist by which displacement behaviour can be recognized, the term is applied to behaviour patterns which appear to be out of context with the behaviour which closely precedes or follows them, either in the sense that they do not seem functionally integrated with the preceding or following behaviour or that they occur in situations in which causal factors usually responsible for them appear to be absent or at least weak compared with those determining the behavioural envelope. Displacement activities occur in three situations: motivational conflict, frustration of consummatory acts and physical thwarting of performance. Several theories have been put forward to explain the causal mechanism involved5–8. A variety of behaviour patterns have been reported as displacement activities9, even in a single species, but this variety needs revision10. Monographic treatments of the behaviour of any one species usually indicate only two or three activities which according to the judgment of the observer occur commonly as displacement. None of the theories on displacement activities gives cogent reasons why particular behaviour patterns should be more common than others as displacement activities, apart from stating that the causal agents which usually elicit them in non-displacement situations can also be presumed to be present, if only weakly, in the displacement context, or remarking that these patterns are prepotent in the repertoire of the animal.