Habituation - History of The Term

History of The Term

The habituation process is a form of adaptive behavior (or neuroplasticity) that is classified as nonassociative learning. Nonassociative learning is a change in a response to a stimulus that does not involve associating the presented stimulus with another stimulus or event such as reward or punishment. (Examples of associative learning include classical conditioning and operant conditioning). Habituation is the decrease of a response to a repeated eliciting stimulus that is not due to sensory adaption or motor fatigue. Sensory adaptation (or neural adaptation) occurs when an animal can no longer detect the stimulus as efficiently as when first presented and motor fatigue suggests that an animal is able to detect the stimulus but can no longer respond efficiently. Habituation as a nonassociative process, however, is a learned adaption to the repeated presentation of a stimulus, not a reduction in sensory or motor ability. Early studies relied on the demonstration of dishabituation (the brief recovery of the response to the eliciting stimulus when another stimulus is added) to distinguish habituation from sensory adaptation and fatigue. More recently stimulus specificity and frequency-dependent spontaneous recovery have been identified as experimental evidence for the habituation process. Sensitization is also conceptualized as a nonassociative process because it involves an increase in responding with repeated presentations to a single stimulus. Much less is understood about sensitization than habituation, but the sensitization process is often observed along with the habituation process.

Drug habituation - While habituation is defined as a process that decreases a behavioral response to a recurring stimulus, there is an additional connotation to the term habituation which applies to drugs and habits. For example, an alternative use of the term habituation involving psychological dependency on drugs is included in several online dictionaries. The origin of this use of the term is instructive. A team of specialist from the World Health Organization (WHO) assembled in 1957 to address the problem of drug addiction and adopted the term “drug habituation” to distinguish some drug-use behaviors from drug addiction. According to the WHO lexicon of alcohol and drug terms, habituation is defined as “becoming accustomed to any behavior or condition, including psychoactive substance use”. By 1964 the America Surgeon’s General report on smoking and health included four features that characterize drug habituation according to WHO: 1) “a desire (but not a compulsion) to continue taking the drug for the sense of improved well-being which it engenders”; 2) “little or no tendency to increase the dose”; 3) “some degree of psychic dependence on the effect of the drug, but absence of physical dependence and hence of an abstinence syndrome”; 4)”detrimental effects, if any, primarily on the individual”. However, also in 1964, a committee from the World Health Organization once again convened and decided the definitions of drug habituation and drug addiction were insufficient, replacing the two terms with “drug dependence”. Substance dependence is the preferred term today when describing drug-related disorders whereas the use of the term drug habituation has declined substantially.