Role in Emotional Reactions

In addition to influencing simple innate behaviors such as sucking reflexes
and withdrawal responses, habituation is believed to be responsible for a
number of more complex emotional reactions in humans. Explanations for
the effects of habituation on emotions are derived primarily from the opponent
process theory of motivation.
The opponent process theory holds that each emotional stimulation (or
primary process) initiated by an environmental stimulus is opposed by an
internal process in the organism. The emotional changes that actually occur
in the organism are predicted to result from the net effect of these two processes.
The opponent process detracts from the primary process, and summation
of the two yields a particular emotional response. It is hypothesized
that when the organism is repeatedly stimulated, the primary process is unaffected,
but the opponent process is strengthened, which results in a net
reduction in the overall emotional response. In other words, repeated presentation
of an emotion-arousing stimulus results in habituation in the emotional
response, primarily as a result of the elevated opponent response.
An increase in drug tolerance which results from repeated usage of a
drug is best explained by this kind of habituation. Habitual users of alcohol,
caffeine, nicotine, or various opiate derivatives must consume greater quantities of such drugs each time they are ingested in order to achieve the same
emotional stimulation. Thus, with repeated usage, there is a decline in the
overall emotional response. This decline in the euphoric effects of a drug is
primarily the result of an increase in the opponent process, which can be
characterized as the negative effects of the drug. This is presumably why habitual
users experience severe physiological problems (for example, headaches
or delirium tremens) upon termination of a drug.
Similar patterns of habituation have also been suggested to explain the
human emotional responses associated with love and attachment and the
extreme feelings of euphoria derived from various thrill-seeking activities
such as skydiving. Thus, while habituation and sensitization are simple
forms of learning, they may be involved in a variety of more complex behaviors
and emotions as well.