Recent estimates suggest that approximately 3% to 5% of the population gambles more than is financially responsible (National Gambling Impact Study Commission Report, 1999
), which is up from estimates of 1% reported 20 years ago (Ladouceur, Boisvert, Pepin, Loranger, & Sylvain, 1994
). Excessive or pathological gambling is considered a type of impulse control disorder by the Diagnostic and Statistical Manual of Mental Disorders
; American Psychiatric Association, 2000
), whereby the gambler displays high levels of impulsivity. Behavioral conceptualizations of the construct of impulsivity
have been noted as the individual's selecting an immediate smaller reinforcer over a larger delayed reinforcer (Critchfield & Kollins, 2001
). Choosing the latter alternative is termed self-control
(Rachlin & Green, 1972
). Over the past decade, there has been a growing literature conceptualizing some maladaptive behavior as problems of intertemporal choice (Bickel & Vuchinich, 2002
; Critchfield & Kollins; Herrnstein & Prelec, 1992
). Behaviors such as compulsive gambling and habitual substance abuse, for example, have been conceptualized as repeated choices between the relatively punctuated and proximal consequences of engaging in the behavior (i.e., intoxication or winning a jackpot) and the relatively diffuse and distal consequences of abstaining from the problem behavior (i.e., a healthier lifestyle or fiscal security). Consistent with this interpretation, a number of studies have demonstrated that these behavioral problems are often correlated with diminished sensitivity to the larger yet delayed outcomes (Dixon, Marley, & Jacobs, 2003
; Madden, Petry, Badger, & Bickel, 1997
; Petry & Casarella, 1999
In these studies, researchers often compared the delay discounting of people diagnosed with impulse control disorders (i.e., substance dependence or compulsive gambling) to the discounting of matched control participants using a hypothetical choice task that was developed by Rachlin, Raineri, and Cross (1991)
. Using this task, participants are required to make repeated choices between immediate and delayed hypothetical consequences (e.g., hypothetical amounts of money or drugs). The delay to the deferred outcome is held constant within conditions but is varied across conditions. Within each delay condition, the amount of the immediate consequence is varied across choices to determine the point of subjective equivalence (i.e., an indifference point) between the immediate and delayed consequences.
The resulting indifference curves are generally consistent with the following hyperbolic model introduced by Mazur (1987)
In Equation 1, V
is the subjective value of the delayed consequence (i.e., the indifference point), A
is the nominal amount of delayed consequence, D
is the delay to deferred consequence, and k
is a free parameter that describes sensitivity to change in delay. The degree of discounting parameter, k
, provides a convenient index of sensitivity to delayed consequences. Higher k
values indicate lower sensitivity to delayed consequences. That is, for any given amount and delay, lower indifference points will yield higher derived k
Consistent with the interpretation that some maladaptive behavior may be functionally related to diminished sensitivity to delayed or diffuse consequences, derived k
values for individuals with impulse control disorders tend to be higher than those for participants who do not display the maladaptive behavior. Opioid-dependent individuals, for example, discount delayed consequences more severely than do matched control participants (Madden et al., 1997
). Likewise, self-identified heavy drinkers discount delayed consequences more severely than self-identified light drinkers (Vuchinich & Simpson, 1999
), cigarette smokers discount more severely than nonsmokers (Odum, Madden, & Bickel, 2002
), and pathological gamblers discount more severely than matched control participants (Dixon et al., 2003
). Moreover, it appears that differences in delay discounting may also be correlated with the severity of the maladaptive behavior. Opioid-dependent individuals with comorbid gambling problems, for example, discount delayed consequences more severely than opioid-dependent individuals without the dual diagnosis (Petry & Casarella, 1999
). Likewise, opioid-dependent individuals who express willingness to use a hypodermic needle after someone else has used it discount delayed monetary and heroin outcomes more severely than those who refuse to use the dirty needle (Odum, Madden, Badger, & Bickel, 2000
). The converging pattern of evidence does much to support the contention that maladaptive impulse control disorders may be functionally related to a general deficit in sensitivity to delayed or diffuse consequences.
Although the aforementioned data greatly extend the external validity of the hypothetical choice task (Rachlin et al., 1991
) and Mazur's (1987)
hyperbolic model of temporal discounting, many questions remain regarding the origins of these individual differences in temporal discounting and the dynamics of temporal discounting. A number of reinforcement variables, for example, have been shown to influence delay discounting, including reinforcement magnitude, commodity type, schedule dynamics, and deprivation. In the hypothetical choice task, adults typically discount smaller money amounts more rapidly than they discount larger money amounts (Green, Myerson, & McFadden, 1997
). Moreover, qualitatively different reinforcers are sometimes discounted to different degrees. Substance-dependent individuals, for example, tend to discount delayed drug reinforcers to a greater degree than a yoked amount of delayed money (Madden, Bickel, & Jacobs, 1999
; Madden et al., 1997
). Schedule manipulations have also been shown to affect delay discounting. Ostaszewski, Green, and Meyerson (1998)
, for example, demonstrated that currencies subject to rapid inflation are discounted more severely than yoked amounts of a more economically stable currency. Deprivation has also been shown to affect delay discounting. Giordano et al. (2002)
studied the effects of drug deprivation on delay discounting in opioid-dependent outpatients receiving buprenorphine pharmacotherapy. Degree of deprivation was manipulated within participants by asking them to complete hypothetical choice assessments either before (i.e., while experiencing mild opioid withdrawal) or 2 hr following (i.e., while experiencing peak drug effects) buprenorphine administration. Participants discounted delayed monetary and drug reinforcers to a greater degree under the deprived conditions. Each of these reinforcement variables suggest an area of concern for those interested in developing interventions to treat impulse control disorders that may be related to delay discounting.
From a therapeutic perspective, understanding the effects of antecedent control of delay discounting may be of critical importance in developing effective interventions for impulse control disorders such as drug dependence or compulsive gambling. For someone struggling with these behavioral problems, merely encountering contexts that have been correlated with reinforcement of the problem behavior may be sufficient to induce relapse. For example, while in a weekly therapy session, a pathological gambler may have every intention of quitting gambling, and believes that his life will now change. However, after removal from the therapy setting, now on his way home passing a casino, quitting gambling seems much less possible. The propensity to relapse towards engaging in the maladaptive behavior may be indicated by varying degrees of discounting. What seems perplexing to researchers and treatment providers in the area of gambling addiction is that while claiming to want and need to stop gambling, the problem gambler often fails at doing so. Failed attempts by the pathological gambler may be considered the result of a disease, an impulsive personality, or lack of willpower. Yet, behaviorally, it may be the case that the pathological gambler discounts the delayed outcomes of terminating gambling, and the degree to which they do varies with the environmental arrangement in which he finds himself. Thus, while in the therapist's office or at home with a family member, the future consequences of quitting gambling are more psychologically present than while only footsteps from a casino.
In the present study we examined the effects of context on delay discounting of problem gamblers. Specifically, we performed within-participant comparisons of delay discounting in gambling (an off-track betting facility) and nongambling (e.g., a coffee shop) contexts to determine if delayed hypothetical money amounts were discounted to a higher degree in the gambling context.