Habituation - Theories of Habituation

Theories of Habituation

In an article written 20 years after his initial research with Groves, renowned authority on the behavioral phenomenon of habituation, Richard F. Thompson, reviews several theories of the process of habituation. The Stimulus-Model Comparator theory formulated by Evgeny Sokolov, and the Groves and Thompson Dual-Process Theory are two examples.

The Stimulus-Model Comparator theory emerged from the research of Sokolov who used the orienting response as the cornerstone of his studies, and operationally defining the orienting response as EEG activity. Orienting responses are heightened sensitivity experienced by an organism when exposed to a new or changing stimulus. Orienting responses can result in overt, observable behaviors as well as psychophysiological responses such as EEG activity and undergo habituation with repeated presentation of the eliciting stimulus. The Sokolov model assumes that when a stimulus is experienced several times the nervous system creates a model of the expected stimulus (a stimulus model). With additional presentations of the stimulus the experienced stimulus is compared with the stimulus model. If the experienced stimulus matches the stimulus model responding is inhibited. At first the stimulus model is not a very good representation of the presented stimulus and therefore there is a mismatch and responding continues, but with additional presentations the stimulus model is improved; consequently there is no longer a mismatch and responding is inhibited causing habituation. However, if the stimulus is changed so that it no longer matches the stimulus model the inhibition of the orienting response is weakened, and an orienting response returns. Sokolov places the location of the Stimulus-Model within the cerebral cortex of the brain.

The Groves and Thompson Dual Process theory of habituation posits that two separate processes exist in the central nervous system that interacts to produce habituation. The two distinct processes are a habituation process and a sensitization process. The dual process theory argues that all noticeable stimuli will elicit both of these processes and that the behavioral output will reflect a summation of both processes. The habituation process is decremental, whereas the sensitization process is incremental enhancing the tendency to respond. Thus when the habituation process exceeds the sensitization process behavior shows habituation, but if the sensitization process exceeds the habituation process, then behavior shows sensitization. Groves and Thompson hypothesize the existence of two neural pathways an “S-R pathway” involved with the habituation process, and a ”state pathway” involved with sensitization. The state system is seen as equivalent to a general state of arousal.