Are there precursors to repression?

The author examines the possibility that repression has developed out of phylo- and ontogenetic precursors. The adaptive task of repression is to control instinctual behavior by screening out those stimuli (internal or external) which could trigger unacceptable behavior. Habituation, i.e., cessation of response to a repeated stimulis, is a mechanism for controlling behavior, with properties strikingly similar to repression. It operates by inhibiting sensory input, can discriminate and "recognize" the stimuli to be inhibited, and is impaired by brain damage, drugs (especially barbiturates), and perhaps also influenced by hypnosis. The author suggests that repression may be an evolutionary step from habituation, providing for inhibition of irrelevant as well as relevant but undesirable stimuli. In infants, habituation and withdrawal of attention from noxious stimuli operate through similar and perhaps identical mechanisms.