The relationship between addiction and reward bundling: an experiment comparing smokers and non-smokers

Previous studies indicate that addicts show reduced preference for more delayed versus more immediate rewards compared to non-addicts. This may reflect a lower propensity to view such decisions in terms of the larger sequences to which they typically belong (e.g. smoking is a frequently repeated act). Therefore, this study aims to test whether, in a sequence of decisions involving smaller, sooner (SS) versus larger, later (LL) rewards, suggesting or forcing people with a propensity to addiction to make the decision for the series as a whole would increase LL preference. It is hypothesized that people without a propensity to addiction should benefit less from being encouraged to think of reward sequences because they already tend to take that view.

Thirty regular smokers (as exemplars of addicted individuals) and 30 non-smokers chose between small short-term and larger long-term monetary rewards over a sequence of four decisions spaced 2 weeks apart. Subjects were divided into three groups: one who made each decision independently with no suggestion that they be considered as a series ('free'), a group to whom it was suggested from the start that they consider each decision as part of the series ('suggested') and a group who were told that their very first choice in the series would be used for the remaining decisions ('forced'). All subjects were paid the amounts they had chosen.

A laboratory room at the University of Cape Town (UCT).

UCT undergraduate volunteers.

The proportion of LL choices in each subgroup was evaluated by χ(2) tests and a probit model.

Smokers increased their preference for LL rewards when 'bundling' of individual decisions into a sequence was either suggested or forced. This preference increased with repeated experience. Non-smokers showed neither pattern.

The propensity of smokers to prefer small short-term rewards over larger delayed rewards may be mitigated, over a sequence of decisions of this kind, by encouraging or forcing them to think of the sequence as a whole. If replicated, this finding may form the basis of an intervention that could attenuate the choice patterns characteristic of addiction.