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. This is not to be confused with true habituation to drugs, wherein repeated doses have an increasingly diminished effect, as is often seen in addicts or persons taking painkillers frequently.

Characteristics
Habituation as a form of non-associative learning can be distinguished from other behavioral changes (e.g., sensory/neural adaptation, fatigue) by considering the characteristics of habituation that have been identified over several decades of research. The characteristics first described by Thompson and Spencer have recently been updated and include the following:

Repeated presentation of a stimulus will cause a decrease in reaction to the stimulus. Habituation is also proclaimed to beRecovery to Rate-of-Stimulation 
 Stimulus-specificity

Early studies relied on the demonstration of 1) Recovery by 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, 2) Sensitivity of Spontaneous Recovery to Rate-of-Stimulation and 3) Stimulus-specificity have been used as experimental evidence for the habituation process.  Spontaneous Recovery is sensitive to spontaneous recovery, showing recovery that is inversely correlated with the amount of response-decline. This is the opposite of what would be expected if sensory adaption or motor fatigue were the cause of the response-decline. Sensory adaptation (or neural adaptation) occurs when an organism can no longer detect the stimulus as efficiently as when first presented and motor fatigue occurs when an organism