Prolonging the effects of deposit contracts with smokers

Three group-comparison studies are reported which investigate possible ways of prolonging the effectiveness and increasing the acceptability of deposit contracts with smokers. In Experiment 1 deposits held for a total of 4 months were compared with those lasting 2 months. In Experiment 2 a ‘reinforcement thinning’ procedure in which the intervals between deposit repayments are progressively increased was compared with contracts involving equal intervals between repayments. In Experiment 3 the effects on compliance, drop-out rates and treatment outcome of a cumulative-deposit procedure were studied. Subjects in this condition were asked to supply a deposit in 4 weekly instalments rather than as a lump sum. The results of Experiments 1 and 2 were disappointing. There were no significant differences between treatments, although there was a trend in favour of ‘thinning’ deposits. Experiment 3, however, showed that the cumulative-deposit procedure was effective in influencing more subjects to provide deposits. Neither drop-out rate nor treatment outcome was adversely affected. It is difficult for a straightforward reinforcement model to account for these results. Other models are discussed, and ways of testing them suggested. A larger study is still needed to determine whether certain deposit-contract procedures can add to the long-term effectiveness of behavioural-package programmes for stopping smoking.