Classical conditioning
Classical conditioning was first investigated, experimentally and systematically, by the Russian physiologist Ivan Pavlov (1928, cited in Mazur, 2002) and has been invoked as the primary process by which environmental (exteroceptive) or internal (interoceptive) cues associated with drinking in the past can come to elicit craving for alcohol in the present.
According to Pavlovâs classical conditioning model, a neutral stimulus (NS), such as a blue light, can become rewarding and influence our behaviour because it has reliably preceded a reward (e.g. food). In Pavlovâs seminal experiments at the turn of the 20th century, salivation (defined as an unconditioned response; UCR) was demonstrated in dogs presented with food (defined as an unconditioned stimulus; UCS). After a bell (NS) was presented in combination with food (UCS) on a number of occasions, the bell became capable of eliciting salivation (originally an UCR) in the absence of food. Thus the bell had become a conditioned stimulus (CS) and salivation a conditioned response (CR). Diagrammatically presented:
Before conditioning | During conditioning | After conditioning |
Foodâsalivation | Bellâfoodâsalivation | Bellâsalivation |
UCSâUCR | NSâUCSâUCR | CSâCR |
As an example of classical conditioning applied to problem drinking, consider an individual who drinks in a pub. Alcohol use (UCS) that elicits pleasure (UCR) is paired with a pub (NS) until the pub itself becomes a CS, eliciting a CR. The exact nature of this CR has been debated by many. One possibility is that the response is similar to the withdrawal that occurs when the alcohol that the body has learned to âexpectâ is not provided (Ludwig & Wikler, 1974). In other words, exposure to alcohol-related cues would trigger the same responses elicited by withdrawal (such as increased heart rate and salivation). Another hypothesis is that the response is a conditioned compensatory response, that is, a physiological response designed to offset the effects of alcohol (Siegel, 1983). This compensatory process is presumed to facilitate the maintenance of homeostasis in an organism that would otherwise be disturbed by the effects of alcohol. A third possibility (Stewart, Dewit, & Eikelboom, 1984) is that a conditioned appetitive response occurs. This response is similar to that produced by alcohol itself (such as decreased blood pressure), or responses connected with seeking and attaining alcohol (such as arousal to prepare for the activities involved in getting alcohol, and salivation to prepare for ingestion). Evidence suggests that alcohol cues most strongly resemble conditioned appetitive responses (Niaura et al., 1988).
A series of factors will determine whether a CS (e.g. a pub) will elicit a CR (e.g. craving) and include the frequency with which the NS and UCS have been originally paired, the intensity of the CS when it is presented, and the psycho-physiological state of the organism at the time the CS is presented. Classical conditioning theory postulates that problem drinkers actually condition many stimuli in the environment (e.g. paraphernalia) by using alcohol repeatedly, in specific settings, with specific people, and according to specific rituals. The types and varieties of cues that become the CS for alcohol use can therefore be vast, and particular to each individual experience of problem drinking.
Classical conditioning has formed the basis of three prominent therapeutic interventions for problem drinking that will now be briefly reviewed, and also forms part of the theoretical basis for coping skills training (Monti et al., 2002). With the exception of aversion therapies, all these interventions attempt, at least in part, to break the conditioned connection between specific aspects of a drinkerâs environment and the appetitive responses (craving) presumed to form the motivational basis for alcohol use.
Aversion conditioning
This therapeutic intervention is designed to moderate the reinforcing properties of alcohol by altering the valence of alcohol-related cues (from positive to negative) through counter-conditioning procedures (Howard et al., 1991; Rimmele, Howard, & Hilfrink, 1995). Counter-conditioning entails pairing a CS (like the taste, smell or sight of alcohol) with an aversive stimulus (i.e. one that creates an unpleasant response) so as to condition a new aversive response to both alcohol use and its cues. The conditioning can be accomplished by several means, including apneic paralysis, chemical agents, electric shock or imaginal strategies (also known as covert sensitization). For example, in covert sensitization the image of a drinking situation (e.g. being at a pub) is paired with an imaginal aversive stimulus (e.g. a scene in which the client vomits all over himself or herself).
Stimulus control
This therapeutic intervention is designed to alter environmental cues for drinking by avoiding the cues, rearranging them or implementing different responses in the same environment. For example, avoiding high-risk situations such as going to a pub with friends who are heavy drinkers or walking home from work down a different road so as to avoid specific cues (e.g. a pub).
Cue exposure and response prevention
This therapeutic intervention is designed to extinguish conditioned responses, such as craving, through repeated exposure to the conditioned stimuli (e.g. smell of beer, negative emotion) without the client being able to execute the conditioned response (using alcohol) (OâBrien et al., 1990; Rohsenow et al., 1991).
Operant conditioning
Operant conditioning, or instrumental learning, refers to the way in which the consequences of a behaviour influence the likelihood of that behaviour being repeated (Skinner, 1969; Mazur, 2002). Reinforcement and punishment are the core domains of operant conditioning. These can be either positive (delivered following a response) or negative (withdrawn following a response). This creates a total of four basic consequences: positive and negative reinforcement, and positive and negative punishment.
Positive reinforcement occurs when a response is followed by a favourable stimulus that increases the frequency of a given behaviour. A problem drinker using alcohol (performing an operant response) to attain a feeling of elation is an example of this. Negative reinforcement occurs when a response is followed by the removal of an aversive stimulus thereby increasing the given behaviourâs frequency. In the case of a problem drinker, they may use alcohol (perform an operant response) to avoid experiencing craving or to impede withdrawal symptoms. Positive punishment occurs when a response is followed by an aversive stimulus, such as introducing a shock or loud noise, resulting in a decrease of that behaviour. For a problem drinker this may occur if drinking patterns result in punishment such as the suspension of a driving licence following a drink-driving episode. Negative punishment occurs when a response is followed by the removal of a favourable stimulus following an undesired behaviour, resulting in a decrease in that behaviour. For a problem drinker this may occur if drinking patterns result in a partner or spouse withdrawing attention or approval. Extinction occurs when any response that had previously been reinforced is no longer effective.
A wide variety of factors will determine alcoholâs capacity to act as a reinforcer. For example, the effectiveness of the consequences of alcohol use will be reduced if the individualâs âappetiteâ for that source of stimulation has been satisfied. Inversely, the effectiveness of the consequence of alcohol use will increase as the individual becomes deprived of that stimulus. After a response, the immediacy of the felt consequences will determine their effectiveness. More immediate feedback will be more effective than less immediate feedback. If a consequence does not reliably or consistently follow the target response, its effectiveness upon the response will be reduced. However, if a consequence follows the response reliably after successive instances, its ability to modify the response will be increased. Finally, there is a âcost-benefitâ determinant of whether a consequence will be effective. If the size, or amount, of the consequence is large enough to be worth the effort, the consequence will be more effective upon the behaviour. It is important to emphasize that these operant mechanisms function primarily outside conscious awareness.
Operant conditioning has formed the basis of a prominent therapeutic intervention for problem drinking known as contingency management. This intervention is aimed at helping the client re-structure their immediate environments in order to decrease the rewards and increase the costs associated with problem drinking (Higgins, Silverman, & Heil, 2003; Miller, 1975). Strategies typically include:
providing incentives for compliance with therapy
positive reinforcement for sobriety (from spouse or friends, for example) and
negative punishment, in the form of withdrawal of attention and approval, contingent on the resumption of excessive alcohol use