Editing Operant conditioning (section)

===Addiction and dependence===

Positive and negative reinforcement play central roles in the development and maintenance of [[addiction]] and [[drug dependence]]. An addictive drug is [[reward system|intrinsically rewarding]]; that is, it functions as [[#Primary reinforcers|a primary positive reinforcer]] of drug use. The brain's reward system assigns it [[incentive salience]] (i.e., it is "wanted" or "desired"),<ref name="Reinforcement in addiction">{{cite book|year=2016|chapter=Reinforcement principles for addiction medicine; from recreational drug use to psychiatric disorder|journal=Prog. Brain Res.|volume=223|pages=63–76|doi=10.1016/bs.pbr.2015.07.005|pmid=26806771|quote=Abused substances (ranging from alcohol to psychostimulants) are initially ingested at regular occasions according to their positive reinforcing properties. Importantly, repeated exposure to rewarding substances sets off a chain of secondary reinforcing events, whereby cues and contexts associated with drug use may themselves become reinforcing and thereby contribute to the continued use and possible abuse of the substance(s) of choice.&nbsp;...<br />An important dimension of reinforcement highly relevant to the addiction process (and particularly relapse) is secondary reinforcement (Stewart, 1992). Secondary reinforcers (in many cases also considered conditioned reinforcers) likely drive the majority of reinforcement processes in humans. In the specific case of drug [addiction], cues and contexts that are intimately and repeatedly associated with drug use will often themselves become reinforcing&nbsp;... A fundamental piece of Robinson and Berridge's incentive-sensitization theory of addiction posits that the incentive value or attractive nature of such secondary reinforcement processes, in addition to the primary reinforcers themselves, may persist and even become sensitized over time in league with the development of drug addiction (Robinson and Berridge, 1993).&nbsp;...<br />Negative reinforcement is a special condition associated with a strengthening of behavioral responses that terminate some ongoing (presumably aversive) stimulus. In this case we can define a negative reinforcer as a motivational stimulus that strengthens such an "escape" response. Historically, in relation to drug addiction, this phenomenon has been consistently observed in humans whereby drugs of abuse are self-administered to quench a motivational need in the state of withdrawal (Wikler, 1952).|vauthors=Edwards S|title=Neuroscience for Addiction Medicine: From Prevention to Rehabilitation - Constructs and Drugs|series=Progress in Brain Research|isbn=9780444635457}}</ref><ref name="Incentive salience and motivation review">{{cite journal|date=April 2012|title=From prediction error to incentive salience: mesolimbic computation of reward motivation|journal=Eur. J. Neurosci.|volume=35|issue=7|pages=1124–1143|doi=10.1111/j.1460-9568.2012.07990.x|pmc=3325516|pmid=22487042|quote=When a Pavlovian CS+ is attributed with incentive salience it not only triggers 'wanting' for its UCS, but often the cue itself becomes highly attractive – even to an irrational degree. This cue attraction is another signature feature of incentive salience. The CS becomes hard not to look at (Wiers & Stacy, 2006; Hickey et al., 2010a; Piech et al., 2010; Anderson et al., 2011). The CS even takes on some incentive properties similar to its UCS. An attractive CS often elicits behavioral motivated approach, and sometimes an individual may even attempt to 'consume' the CS somewhat as its UCS (e.g., eat, drink, smoke, have sex with, take as drug). 'Wanting' of a CS can turn also turn the formerly neutral stimulus into an instrumental conditioned reinforcer, so that an individual will work to obtain the cue (however, there exist alternative psychological mechanisms for conditioned reinforcement too).|vauthors=Berridge KC}}</ref><ref name="Pleasure system - incentive sensitization">{{cite journal|date=May 2015|title=Pleasure systems in the brain|journal=Neuron|volume=86|issue=3|pages=646–664|doi=10.1016/j.neuron.2015.02.018|pmc=4425246|pmid=25950633|quote=An important goal in future for addiction neuroscience is to understand how intense motivation becomes narrowly focused on a particular target. Addiction has been suggested to be partly due to excessive incentive salience produced by sensitized or hyper-reactive dopamine systems that produce intense 'wanting' (Robinson and Berridge, 1993). But why one target becomes more 'wanted' than all others has not been fully explained. In addicts or agonist-stimulated patients, the repetition of dopamine-stimulation of incentive salience becomes attributed to particular individualized pursuits, such as taking the addictive drug or the particular compulsions. In Pavlovian reward situations, some cues for reward become more 'wanted' more than others as powerful motivational magnets, in ways that differ across individuals (Robinson et al., 2014b; Saunders and Robinson, 2013).&nbsp;... However, hedonic effects might well change over time. As a drug was taken repeatedly, mesolimbic dopaminergic sensitization could consequently occur in susceptible individuals to amplify 'wanting' (Leyton and Vezina, 2013; Lodge and Grace, 2011; Wolf and Ferrario, 2010), even if opioid hedonic mechanisms underwent down-regulation due to continual drug stimulation, producing 'liking' tolerance. Incentive-sensitization would produce addiction, by selectively magnifying cue-triggered 'wanting' to take the drug again, and so powerfully cause motivation even if the drug became less pleasant (Robinson and Berridge, 1993).|vauthors=Berridge KC, Kringelbach ML}}</ref> so as an addiction develops, deprivation of the drug leads to craving.  In addition, stimuli associated with drug use&nbsp;– e.g., the sight of a syringe, and the location of use&nbsp;– become associated with the intense reinforcement induced by the drug.<ref name="Reinforcement in addiction" /><ref name="Incentive salience and motivation review" /><ref name="Pleasure system - incentive sensitization" /> These previously neutral stimuli acquire several properties: their appearance can induce craving, and they can become [[#Secondary reinforcers|conditioned positive reinforcers]] of continued use.<ref name="Reinforcement in addiction" /><ref name="Incentive salience and motivation review" /><ref name="Pleasure system - incentive sensitization" /> Thus, if an addicted individual encounters one of these drug cues, a craving for the associated drug may reappear. For example, anti-drug agencies previously used posters with images of [[drug paraphernalia]] as an attempt to show the dangers of drug use. However, such posters are no longer used because of the effects of incentive salience in causing [[relapse]] upon sight of the stimuli illustrated in the posters.

In drug dependent individuals, negative reinforcement occurs when a drug is [[self-administration|self-administered]] in order to alleviate or "escape" the symptoms of [[physical dependence]] (e.g., [[tremor]]s and sweating) and/or [[psychological dependence]] (e.g., [[anhedonia]], restlessness, irritability, and anxiety) that arise during the state of [[drug withdrawal]].<ref name="Reinforcement in addiction" />