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sources of reinforcement. Russell (1971) and Russell et al. (1974) found that nicotine use was reinforced more often by social sources in the early stages of use, followed by pharmacological sources (the positive reinforcement potential of the drug effect and the negative reinforcement potential of avoiding the loss of the effect), followed by physiological sources (the negative reinforcement potential of avoiding or ameliorating withdrawal symptoms). While social rewards may change across the life span, pharmacological and physiological rewards, being internal in their source may account for the persistence and intensification of dependence and will be discussed further in the next section.
In the present study, the question of the sequencing of symptoms was examined and it was found that when individual item scores were plotted against severity, all item scores increased more or less consistently with increasing severity. No difference was found between users of the two study drugs, heroin and alcohol, pointing to the possibility that their different reinforcement potential results in varying rates in the development of dependence rather than in a different sequence in the development of specific components. Varying rates in the development of dependence are suggested by the finding of significantly shorter duration of use and of problem use prior to attendance at the treatment agency in the heroin group (see Chapter 7).
2.2 The maintenance of dependence
While there is no obvious temporal or qualitative distinction between the development of dependence and its maintenance, for the purpose of this discussion the question of how dependence is maintained in the face of sometimes adverse consequences is considered.
“Dependence is not then seen as an all-or-none phenomenon: its severity is judged by the strength of a conditioning process” (Edwards et al. 1972 p. 418)
Edwards et al. (1972) used a simple scale to measure the presence and severity of alcohol dependence which consisted of two questions: “have you ever woken up with your hands very shaky as a result of the previous night’s drinking?” and “have you ever taken a morning drink to steady yourself after a hard night’s drinking?” Respondents were asked to reply in one of three categories: never, once or twice or more than once or twice. These simple questions carried three assumptions about the nature of alcohol dependence: one was that if you had ever had it you would
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