ERIC EJ750844: Contextual Control of Delay Discounting by Pathological Gamblers

2006·0.21 MB·English

by  ERIC

JOURNALOFAPPLIEDBEHAVIORANALYSIS 2006, 39, 413–422 NUMBER4 (WINTER2006)
CONTEXTUAL CONTROL OF DELAY
DISCOUNTING BY PATHOLOGICAL GAMBLERS
MARK R. DIXON, ERIC A. JACOBS, AND SCOTT SANDERS
SOUTHERNILLINOISUNIVERSITY
Thepresentstudydemonstratedtherelativeimpactofgamblingandnongamblingcontextson
thedegreeofdelaydiscountingbypathologicalgamblers.Weusedadelay-discountingtaskwith
20pathologicalgamblersinandoutofthenaturalcontextinwhichtheyregularlygambled.For
16ofthe20participants,itappearedthatthedifferenceofcontextalteredthesubjectivevalueof
delayed rewards, thereby producing relative changes in delay-discounting rates that were
generallyconsistentwithahyperbolicmodelofintertemporalchoice.Thecurrentdatasuggest
thatempirically derivedkvaluesfromdelay-discountingtasksarecontextsensitiveandarenot
constantacrossvarioussettingsfortheindividual.Implicationsforfuturetransitionalresearchon
addictive disorders generally,andgambling specifically, arediscussed.
DESCRIPTORS: choice, self-control, impulsivity, delay discounting, establishing opera-
tion, gambling
_______________________________________________________________________________
Recent estimates suggest that approximately has been a growing literature conceptualizing
3%to5%ofthepopulationgamblesmorethan some maladaptive behavior as problems of
is financially responsible (National Gambling intertemporal choice (Bickel & Vuchinich,
Impact Study Commission Report, 1999), 2002; Critchfield & Kollins; Herrnstein &
which is up from estimates of 1% reported 20 Prelec, 1992). Behaviors such as compulsive
years ago (Ladouceur, Boisvert, Pepin, Loran- gambling and habitual substance abuse, for
ger,&Sylvain,1994).Excessiveorpathological example, have been conceptualized as repeated
gambling is considered a type of impulse choices between the relatively punctuated and
controldisorderbytheDiagnosticandStatistical proximal consequences of engaging in the
Manual of Mental Disorders (DSM-IV-TR; behavior(i.e.,intoxicationorwinningajackpot)
American Psychiatric Association, 2000), and the relatively diffuse and distal conse-
whereby the gambler displays high levels of quences of abstaining from the problem
impulsivity. Behavioral conceptualizations of behavior (i.e., a healthier lifestyle or fiscal
the construct of impulsivity have been noted as security). Consistent with this interpretation,
the individual’s selecting an immediate smaller a number of studies have demonstrated that
reinforcer over a larger delayed reinforcer these behavioral problems are often correlated
(Critchfield & Kollins, 2001). Choosing the with diminished sensitivity to the larger yet
latter alternative is termed self-control (Rachlin delayed outcomes (Dixon, Marley, & Jacobs,
& Green, 1972). Over the past decade, there 2003; Madden, Petry, Badger, & Bickel, 1997;
Petry & Casarella, 1999).
In these studies, researchers often compared
This study was completed in partial fulfillment of the
MS degree in behavior analysis and therapy by the third the delay discounting of people diagnosed with
authorunderthedirectionofthefirstandsecondauthors impulse control disorders (i.e., substance de-
and Brandon F. Greene. We thank the University
pendence or compulsive gambling) to the
TeletrackofCarbondale,Illinois,forallowingthisresearch
discounting of matched control participants
totakeplace.
AddressallcorrespondencetoMarkR.Dixon,Behavior using a hypothetical choice task that was
Analysis and Therapy Program, Rehabilitation Institute, developed by Rachlin, Raineri, and Cross
Southern Illinois University, Carbondale, Illinois 62901
(1991). Using this task, participants are re-
(e-mail: [email protected]).
doi:10.1901/jaba.2006.173-05 quired to make repeated choices between
413
414 MARK R. DIXON et al.
immediate and delayed hypothetical conse- theseverityofthemaladaptivebehavior.Opioid-
quences (e.g., hypothetical amounts of money dependent individuals with comorbid gambling
or drugs). The delay to the deferred outcome is problems, for example, discount delayed con-
held constant within conditions but is varied sequences more severely than opioid-dependent
across conditions. Within each delay condition, individuals without the dual diagnosis (Petry &
the amount of the immediate consequence is Casarella, 1999). Likewise, opioid-dependent
varied across choices to determine the point of individuals who express willingness to use
subjective equivalence (i.e., an indifference ahypodermicneedleaftersomeoneelsehasused
point) between the immediate and delayed it discount delayed monetary and heroin out-
consequences. comesmoreseverelythanthosewhorefusetouse
The resulting indifference curves are gener- the dirty needle (Odum, Madden, Badger, &
ally consistent with the following hyperbolic Bickel, 2000). The converging pattern of
model introduced by Mazur (1987): evidence does much to support the contention
V ~A=(1 z kD): ð1Þ that maladaptive impulse control disorders may
be functionally related to a general deficit in
In Equation 1, V is the subjective value of the
sensitivity to delayed or diffuse consequences.
delayed consequence (i.e., the indifference
Although the aforementioned data greatly
point), A is the nominal amount of delayed
extend the external validity of the hypothetical
consequence, D is the delay to deferred con-
choice task (Rachlin et al., 1991) and Mazur’s
sequence, and k is a free parameter that
(1987) hyperbolic model of temporal discount-
describes sensitivity to change in delay. The
ing, many questions remain regarding the
degree of discounting parameter, k, provides
origins of these individual differences in
a convenient index of sensitivity to delayed
temporal discounting and the dynamics of
consequences. Higher k values indicate lower
temporal discounting. A number of reinforce-
sensitivity to delayed consequences. That is, for
ment variables, for example, have been shown
any given amount and delay, lower indifference
to influence delay discounting, including re-
points will yield higher derived k values.
inforcement magnitude, commodity type,
Consistent with the interpretation that some
schedule dynamics, and deprivation. In the
maladaptivebehaviormaybefunctionallyrelated
hypothetical choice task, adults typically dis-
to diminished sensitivity to delayed or diffuse
consequences, derived k values for individuals count smaller money amounts more rapidly
withimpulsecontroldisorderstendtobehigher than they discount larger money amounts
than those for participants who do not display (Green, Myerson, & McFadden, 1997). More-
the maladaptive behavior. Opioid-dependent over, qualitatively different reinforcers are
individuals, for example, discount delayed con- sometimes discounted to different degrees.
sequencesmoreseverelythandomatchedcontrol Substance-dependent individuals, for example,
participants (Madden et al., 1997). Likewise, tend to discount delayed drug reinforcers to
self-identified heavy drinkers discount delayed agreaterdegreethanayokedamountofdelayed
consequences more severely than self-identified money (Madden, Bickel, & Jacobs, 1999;
light drinkers (Vuchinich & Simpson, 1999), Madden et al., 1997). Schedule manipulations
cigarette smokers discount more severely than have also been shown to affect delay discount-
nonsmokers(Odum,Madden,&Bickel,2002), ing. Ostaszewski, Green, and Meyerson (1998),
andpathologicalgamblersdiscountmoresevere- for example, demonstrated that currencies sub-
ly than matched control participants (Dixon et ject to rapid inflation are discounted more
al., 2003). Moreover, it appears that differences severely than yoked amounts of a more eco-
indelaydiscountingmayalsobecorrelatedwith nomically stable currency. Deprivation has also
DELAY DISCOUNTING 415
been shown to affect delay discounting. Gior- terminating gambling, and the degree to which
dano et al. (2002) studied the effects of drug they do varies with the environmental arrange-
deprivation on delay discounting in opioid- ment in which he finds himself. Thus, while in
dependent outpatients receiving buprenorphine the therapist’s office or at home with a family
pharmacotherapy. Degree of deprivation was member, the future consequences of quitting
manipulatedwithinparticipantsbyaskingthem gambling are more psychologically present than
to complete hypothetical choice assessments while only footsteps from a casino.
either before (i.e., while experiencing mild In the present study we examined the effects
opioidwithdrawal)or2 hrfollowing(i.e.,while of context on delay discounting of problem
experiencing peak drug effects) buprenorphine gamblers. Specifically, we performed within-
administration. Participants discounted delayed participant comparisons of delay discounting in
monetary and drug reinforcers to a greater gambling (an off-track betting facility) and
degree under the deprived conditions. Each of nongambling (e.g., a coffee shop) contexts to
these reinforcement variables suggest an area of determine if delayed hypothetical money
concern for those interested in developing amounts were discounted to a higher degree
interventions to treat impulse control disorders in the gambling context.
that may be related to delay discounting.
Fromatherapeuticperspective,understanding METHOD
the effects of antecedent control of delay
Participants and Setting
discounting may be of critical importance in
Twenty participants were recruited to partic-
developing effective interventions for impulse
ipate (19 men and 1 woman, mean age 5 37
control disorders such as drug dependence or
years). Each participant completed the South
compulsive gambling. For someone struggling
Oaks Gambling Scale (SOGS), a 20-item
with these behavioral problems, merely encoun-
questionnaire that assesses pathological gam-
tering contexts that have been correlated with
bling based on DSM-IV-TR (2000) criteria and
reinforcement of the problem behavior may be
has been shown to have acceptable psychomet-
sufficient to induce relapse. For example, while
ric properties (Lesieur & Blume, 1987). Scores
in a weekly therapy session, a pathological
on the SOGS range from 0 to 14, with a score
gambler may have every intention of quitting
of4ormoreindicativeofpotentialpathological
gambling, and believes that his life will now
gambling. The mean SOGS score for the 20
change.However,afterremovalfromthetherapy
participantsinthepresentstudywas6.6(range,
setting, now on his way home passing a casino,
5 to 12).
quittinggamblingseemsmuchlesspossible.The
The gambling context in which sessions took
propensity to relapse towards engaging in the
place was an off-track betting facility. The
maladaptive behavior may be indicated by
facilityhousedtwobars,anumberoftablesand
varying degrees of discounting. What seems
chairs, and approximately 30 televisions broad-
perplexingtoresearchersandtreatmentproviders
casting horse-racing events from all over the
in the area of gambling addiction is that while
world. The nongambling contexts included
claimingtowantandneedtostopgambling,the
coffeeshops,restaurants,orapreferredbusiness
problem gambler often fails at doing so. Failed or public location where the participant would
attempts by the pathological gambler may be be able to perform the delay-discounting task.
considered the result of a disease, an impulsive
personality, or lack of willpower. Yet, behavior- Materials
ally, it may be the case that the pathological A personal computer running a delay-dis-
gambler discounts the delayed outcomes of counting software program was used for data
416 MARK R. DIXON et al.
collection. This program was written in Visual of the first administration of the delay-dis-
Basic.NET by the first author (see Dixon & counting task, all participants rescheduled the
MacLin, 2003). All reward choices were made next session with the experimenter to be
by the participant pointing directly at a hypo- completed in the other context within approx-
thetical amount of money displayed on the imately 1 week.
computer screen. The time delays were 1 week, At the beginning of the first experimental
2 weeks, 1 month, 6 months, 1 year, 3 years, session, the researcher read to participants
and 10 years. The monetary reward amounts a script describing the delay-discounting com-
were $1,000, $990, $960, $920, $850, $800, puter program. In the program, participants
$750, $700, $650, $600, $550, $500, $450, were presented with multiple consecutive mon-
$400, $350, $300, $250, $200, $150, $100, etarychoices.Theparticipantswasinstructedto
$80, $60, $40, $20, and $10; these amounts point to the hypothetical amount of money he
have been used frequently in other studies (e.g., orshewouldratherhave:eitheralargerdelayed
Bickel,Odum,&Madden,1999;Critchfield& rewardorasmallerimmediatereward.Afterthe
Kollins, 2001; Madden et al., 1999; Petry & participant pointed to the desired selection on
Casarella, 1999; Rachlin et al., 1991). the screen, the response was recorded. This
sequence continued for all hypothetical mone-
Procedure
tary rewardson the smaller immediate side. For
Eachparticipantcompletedapreexperimental example, the initial choice presented to the
assessment using the SOGS in the gambling participant was between $1,000 available now
context and two experimental sessions of the or $1,000 available after 1 week. After a partic-
delay-discounting task (one in the gambling ipant selected an amount, the next choice (i.e.,
context and one in the nongambling context), $990 now or $1,000 after 1 week) was
each lasting approximately15 to 25 min. At the presented. The amount of money available
onset of the preexperimental session, which continued to decrease to $10 along the values
took place in the gambling context where describedearlier.Theprocesswasthenrepeated
participants were recruited, the participant read in ascending order (i.e., amounts increasing
a consent form and agreed to complete the from $10 to $1,000 now vs. $1,000 1 week
study. The participants then were verbally later). The ascending and descending sequences
administered the SOGS. The SOGS was then werethenrepeatedatthenextlargerdelayvalue
scored, and participants who did not score 4 or (e.g., $1,000 available now vs. $1,000 available
more (indicative of probable pathological in 2 weeks).
gambling) were dismissed and excluded from
theremainderofthestudy.Furtherquestioning
RESULTS
of the participants revealed that they were
regular patronsof the betting facility,had never The indifference points obtained at each of
attended a Gamblers Anonymous meeting, and the seven delays are shown in Table 1 under
had never sought help for a gambling problem. gambling and nongambling conditions for each
Participants were randomly assigned to context participant. Within each assessment, the in-
order. Participants who were assigned to the difference points usually decreased or remained
gambling context first completed the delay- the same across successive delay values. Each
discounting task. Participants who were as- obtained indifference curve was evaluated
signed to the nongambling context first were according to the following criteria to determine
scheduled to meet the experimenter in such consistency with delay discounting, broadly
a context within the next few days to complete construed. The mean of the indifference points
thedelay-discountingtask.Afterthecompletion from the three shortest delay conditions had to
DELAY DISCOUNTING 417
Table 1
IndifferencePoints,DerivedkValues,ProportionsofVarianceAccountedfor(R2)byEquation1,andAreaUnderthe
Curve (AUC) Measuresfor Each ParticipantUnder Gambling (G)andNongambling (NG) Conditions
Delay(weeks)
Participant Condition 1 2 4 25 52 156 520 k R2 AUC
101 G 750 700 450 250 100 60 60 .2440 0.96 .087
NG 1,000 850 850 550 350 150 150 .0349 0.97 .214
102 G 1,000 1,000 10 10 10 10 10 .2942 0.71 .016
NG 1,000 1,000 1,000 500 400 175 10 .0307 0.98 .184
103 G 850 800 700 550 450 350 250 .0258 0.55 .347
NG 920 850 800 700 550 400 300 .0127 0.75 .409
104 G 700 700 700 500 100 100 60 .1002 0.8 .121
NG 800 800 775 650 200 100 100 .0454 0.87 .157
105 G 1,000 1,000 1,000 650 500 500 500 .0085 0.55 .521
NG 1,000 1,000 1,000 700 550 500 500 .0070 0.61 .529
106 G 1,000 1,000 920 800 650 600 500 .0040 0.68 .590
NG 800 800 700 700 500 400 400 .0137 0.16 .436
107 G 990 990 990 990 990 990 500 .0012 0.82 .819
NG 920 1,000 920 850 800 650 550 .0025 0.71 .651
108 G 850 850 800 700 500 400 10 .0176 0.87 .302
NG 800 750 700 650 600 500 500 .0150 22.72 .526
109 G 920 850 800 750 550 10 10 .0236 0.89 .135
NG 700 700 650 550 500 350 200 .0268 20.18 .335
110 G 920 920 800 750 550 450 10 .0137 0.9 .333
NG 920 920 850 800 700 400 100 .0101 0.95 .364
201 G 875 850 700 550 250 10 10 .0576 0.94 .085
NG 920 920 920 750 550 10 10 .0220 0.93 .138
202 G 550 550 500 500 10 10 10 .3242 0.55 .047
NG 960 920 1,000 500 500 500 10 .0186 0.86 .342
203 G 700 700 800 10 10 10 10 .1877 0.88 .032
NG 1,000 1,000 500 600 10 10 10 .0799 0.83 .054
204 G 850 850 800 700 700 650 550 .0032 21.47 .628
NG 850 850 800 800 700 700 550 .0026 21.09 .655
205 G 920 850 920 600 300 200 100 .0326 0.97 .216
NG 850 850 990 770 700 300 100 .0128 0.92 .321
206 G 600 500 400 250 100 60 10 .4509 0.86 .067
NG 920 750 500 300 100 40 10 .1665 0.97 .064
207 G 1,000 1,000 1,000 850 650 300 250 .0101 0.97 .371
NG 1,000 1,000 920 800 600 400 250 .0099 0.97 .406
208 G 750 700 600 600 450 10 10 .0484 0.65 .110
NG 920 850 750 700 650 10 10 .0223 0.85 .144
209 G 850 850 700 500 250 200 200 .0525 0.87 .235
NG 500 400 400 200 200 200 200 .6232 20.52 .206
210 G 1,000 1,000 1,000 500 300 10 10 .0398 0.96 .097
NG 1,000 1,000 920 700 500 100 10 .0224 0.97 .170
exceedthemeanoftheindifferencepointsfrom the hyperbolic model provided an adequate
the three longest delay conditions, and in- description of the majority of the individual
difference points could not increase across indifference curves. Across all participants and
successive delays more than once. The obtained conditions, the median R2 value was 0.86 and
indifference curves for all participants under all the interquartile range was 0.64 to 0.94. In 12
conditions met these criteria. instances involving 9 participants, however, the
Table 1 also contains the empirically derived proportion of variance accounted for by
discounting parameters (k values) and the Equation 1 fell below 0.7. Such poor fits often
individual proportions of variance (R2) ac- occurred despite orderly indifference curves
counted for by the hyperbolic model for each (e.g., see Participant 103 under the gambling
participant under each condition. In general, condition). Thus, although Equation 1 ade-
418 MARK R. DIXON et al.
Figure 1. k values derived from data obtained in the Figure 2. Area under the indifference curve obtained
gamblingandnongamblingcontextsforselectparticipants in the gambling and nongambling contexts for each
(see text for details). The dashed reference line depicts participant. The dashed reference line depicts equality
equality betweenthe kvalues. between the AUCmeasures.
quately described most of the individual in- indifference curves than other quantitative
difference curves, a subset of the indifference models, such as those based on hyperbolic or
curves may not have been formally consistent exponential delay discounting, that make ex-
with the hyperbolic model. plicit assumptions regarding the form of the
Nonetheless, the k parameter provides a use- indifference curve. The AUC ranges from
ful index of degree of discounting, as higher k 0 (steep discounting) to 1 (little or no
values indicate greater sensitivity to delay to discounting).
reinforcement.Ifthegamblingcontextincreases If the gambling context exacerbates delay
the degree of delay discounting, then the k discounting, then the AUC obtained in the
parameters derived from data collected in the gambling context should be lower than the
gambling context should exceed those derived AUC obtained in the nongambling context.
fromdatacollectedinthenongamblingcontext. Indeed, for 16 of the 20 participants, the AUC
Data from the 11 participants for whom was lower in the gambling context (see
Equation 1 provided an adequate description Figure 2). An analysis of variance was con-
(i.e., R2 .0.7) of the indifference curves from ducted to assess the effects of context and
both contexts are shown in Figure 1. For 10 of sequence of conditions on AUC. The effect of
these 11 participants, the k value derived from sequence was not statistically significant, F(1,
data obtained in the gambling context exceeded 18) 5 2.4480, p 5 .14, nor was the interaction
that derived from data obtained in the between sequence and context, F(1, 18) 5
nongambling context. 0.0220, p 5 .88. However, the main effect of
Area under the indifference curve (AUC), context on AUC was statistically significant,
another measure of delay discounting, is also F(1, 18) 5 4.9788, p 5 .04.
presented in Table 1 for each participant under Figure 3 shows aggregate discounting curves
both conditions. AUC is a theoretically neutral for all participants in gambling and nongam-
measure of delay discounting that requires no bling contexts. The data points represent the
a priori assumptions regarding the form of the medians of the individual indifference points at
indifference curve (Myerson, Green, & War- each delay (see Table 1). Equation 1 provided
usawitharana, 2001). As such, the AUC a good description of the aggregate indifference
measure is applicable to a wider range of curves. The proportions of variance accounted
DELAY DISCOUNTING 419
participants, again demonstrating steeper tem-
poral discounting when gambling. Aggregate
data patterns were in accord with these in-
dividual patterns. However, the aggregate data
were well described by Equation 1. Although
previous research has demonstrated the utility
of the hyperbolic model (Equation 1) to fit
obtained discounting data (e.g., Kirby &
Marakovic, 1995; Kirby, Petry, & Bickel,
1999;Maddenetal.,1997;Mazur,1987;Petry
&Bickel,1998;Rachlinetal.,1991;Raineri&
Rachlin, 1993), our present findings revealed
Figure 3. Aggregate indifference curves for partici- many instances in which this model provided
pants in the gambling and nongambling contexts. Data a relatively poor fit to the obtained individual
points represent medians of the individual indifference
data. The difficulties we had with Equation 1
points. Error bars represent the interquartile range of the
were similar to those reported by Dixon et al.
individualindifferencepointsateachdelay.Thesolidline
showsthebestfitinthegamblingcontext,andthedashed (2003) in a comparison of delay discounting in
lineshows thebest fitin thenongambling context. pathological gamblers and matched controls
and by Dixon et al. (2005) in a comparison of
forbythehyperbolicmodelwere0.96and0.93
delay discounting in persons with acquired
in the gambling and nongambling contexts,
brain injuries and matched controls. As in these
respectively. The derived k value for the
previous studies, AUC measures were deemed
aggregate data was higher for participants in
useful for data analysis. The strength of the
the gambling context (k 5 .0358) than in the
AUC measure is that it is not tied to any
nongambling context (k 5 .0171). The area
particular theory about the form of the in-
under the aggregate curve was also smaller in
difference curve (i.e., hyperbolic or exponential
the gambling context (AUC 5 .1762) than in
discounting).Assuch,itcanbeusedtoevaluate
the nongambling context (AUC 5 .3118).
data that do not conform to existing quantita-
tive models. One weakness of the AUC
DISCUSSION measure, however, is that similar areas may be
obtainedfromverydifferentdiscountingcurves.
The current findings illustrate that most
Nonetheless, AUC analyses are gaining popu-
pathological gamblers discounted delayed re-
larity for analyzing discounting data that may
wardstoagreaterdegreeinagamblingcontext.
For the majority of participants, k values notfit hyperbolicdecayfunctions(Dixon etal.,
derived from fitting Equation 1 to individual 2003, 2005; Myerson et al., 2001), and future
indifference curves were larger in the gambling researchers may wish to compare the two
context than in the nongambling context, metrics with various other clinical populations
indicating more severe discounting when gam- to further establish their concordance.
bling. It should be noted, however, that The present study also underscores the value
Equation 1 did not provide a good fit to the of conducting within-participant analyses of
individual indifference curves for a number of variables that may affect intertemporal choice.
participants, despite relatively orderly discount- Sixteen of our 20 participants showed greater
ing data. Individual AUC measures were also degrees of delay discounting when assessed
smaller in the gambling context than in the within a gambling environment compared to
nongambling context for the majority of a nongambling environment. Although Fig-
420 MARK R. DIXON et al.
ure 3displaysaggregatedifferences in discount- al., 2003; Petry & Casarella, 1999). Our data
ing across contexts, the group analysis may showthatalteringthecontextinwhichthedelay-
obscure the magnitude and consistency of the discounting task is completed can result in
effect. The individual data displayed in Table 1 different degrees of discounting. To date, the
and Figure 2 provide a more refined within- impact of context on altering the behavior of
participant analysis of the subtle changes in pathological gamblers has only been speculative
discounting that occurred for each participant. (Dixon et al., 2003); however, the current data
For example, the interquartile ranges displayed demonstrateempiricalsupportforthisassertion.
inFigure 2illustrateconsiderableoverlapacross Thepresentstudywasconductedinanatural
contexts and could be considered an indication settingand,assuch,suffersfromsomepotential
that the effect of context was not robust. threats to internal validity that should be
However, it is the relative change that occurred recognized. First, our sample may not have
within each individual participant’s discounting been representative of pathological gamblers in
pattern that should be considered our most general. Participants were self-selected volun-
important finding. Consider Participant 101, teers, and the method of identifying patholog-
who displayed an AUC value of .08 in the ical gamblers relied on self-report rather than
gambling context and .21 in the nongambling direct observation of relevant behavior. Al-
context, and Participant 103, who displayed though the SOGS is the primary screening
AUCs of .34 and .40 in those respective instrument in the gambling literature, our
contexts. Both of Participant 101’s AUCs were sample may have been restricted to those
much higher than 103’s (indicating generally pathological gamblers who responded accurate-
greater discounting by 103), but the relative ly to the questionnaire. In addition, the sample
changewithineachparticipantwassimilar.This may have included gamblers who underesti-
illustrates the true value of within-participant mated the prevalence of their gambling. This
analysis. Although both participants had differ- sampling problem seems more likely in that
ent degrees of delay discounting, each was many pathological gamblers may not wish to
relatively equally sensitive to the contextual disclose the severity of their disorder to an
manipulations of the present experiment. unknown researcher. Furthermore, we used
Thepresentfindingsaddtoagrowinglineof only pathological gamblers who were currently
research on variables that affect delay discount- gambling and not seeking treatment for this
ing.Previousresearchhasshownthatseverityof disorder. Thus, our participants may actually
discounting can be affected by conditions of represent the most severe type of pathological
deprivation (Giordano et al., 2002), reinforcer gambler,onewhoiscurrentlygamblingandnot
magnitude (Green et al., 1997), reinforcer type seekingtreatment.Anotherpotentialconfound-
(Bickel et al., 1999; Madden et al., 1997, ing effect is that our current participants were
1999), and history (Bickel et al.). These free to consume alcohol within the gambling
findings are important because they suggest establishment, and drug use may have occurred
that such variables need to be controlled when prior to entering this establishment. Therefore,
conducting discounting assessments and they we are unaware of how substance use may have
provide a rationale for conducting multiple differentially affected our participants’ respond-
assessments within individual participants. ing across the two contexts. Richards, Zhang,
Thepresentdataalsofurtherourunderstand- Mitchell,anddeWit(1999)reported,however,
ing of the discounting behavior of pathological that alcohol consumption did not affect
gamblers, who have been shown to discount to responding on the hypothetical money choice
greaterdegrees than matched controls(Dixon et task in a laboratory context. We were also not
DELAY DISCOUNTING 421
aware of,nor did we control for, the amount of onsetofdisorder,andcurrentindebtednessmay
time the participant was in the gambling be predictive of delay discounting.
establishment or the number of winning or In summary, the present experiment illus-
losing wagers that had been made before trates a clear rationale for conducting trans-
completing our experiment. This latter point lational research on delay discounting. The
begs the question regarding the mechanism context in which the experimental procedures
responsible for behavior change across contexts. were conducted altered the choice patterns for
Relevant variables in the gambling context many of the participants. There is a growing
might include the presence of others who are literature on temporal discounting in people
gambling, alcohol consumption, and the with impulse control disorders. To the extent
amount of money available to participants. It that insensitivity to delayed or diffuse conse-
may have also been the case that the nongam- quences contributes to the provenance and
blingcontextwaslessnaturalorsocialinnature maintenance of these behavioral problems,
than the off-track betting facility. The specific understanding the variables that control tem-
variables that contributed to the between- poraldiscountingisofcriticalimportancetothe
context differences observed in the present development of effective treatments (see, e.g.,
study are unknown, but it seems safe to Petry, 2005). Identifying the conditions under
conclude that a gambling context contains which an individual is most sensitive to the
critical variables that alter delay discounting, long-term consequences of his or her behavior
at least for pathological gamblers. may enhance the likelihood that he or she will
Future researchers may wish to further commit to a course of action that will bring
explore various additional parameters such as behavior under control of those extended
immediate financial instability, which may alter outcomes.Behavioranalystsareuniquelypoised
pathological gamblers’ discounting. Pietras and to advance this research by examining environ-
Hackenberg (2001), for example, have demon- ment-based controlling variables instead of
strated that income and budgetary constraints acceptingprescientific,organism-basedexplana-
affect risky choice in humans in the laboratory. tions for these pervasive and socially significant
In translating the implications of their work to behavioral problems.
gambling, an experimenter might assess how
moment-by-moment wins or losses alter the REFERENCES
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Bickel, W. K., Odum, A. L., & Madden, G. L. (1999).
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