The article looks at a form of individual behaviour - prodromal behaviour - in which all structural components of an action are determined genetically. It differs from instinctive behaviour in its functional characteristics and realization mechanisms achieving a mediated adapting effect due to the fact that it is part of more complex acts of behaviour and does not coincide in time with experiencing an actual need. The statement that prodromal behaviour should be identified as a specific form of behaviour is substantiated by data from ethopsychology, animal psychology, developmental psychology.