Chapter 10 344 scaling up the trial prohibitively costly.17 The standard scheme is identical to the scheme in the CATCH trial.18 Given time discounting due to inflation and individual impatience, it seems natural to apply some compensation in the total potential gains to the descending and ascending scheme. For example, why would someone self-select into an ascending scheme with zero pay-out in the first six months if the total potential gain is the same as the descending scheme where one can cash-in €150,- already after a baseline? Further, as deposit contracts have proven to be most effective among those who choose one,10 we aimed to make this scheme the most attractive by providing the largest total reward size. The key aspect of the intervention is the personalisation of the incentives. The varying values over time and varying total reward sizes allow for differences in reward preferences. For example, those who prefer to earn money sooner can choose accordingly (descending scheme), however, in that case the maximum total amount rewarded will be lower, while patience is rewarded with a higher total amount (ascending scheme). Halpern et al.10 showed that in the context of smoking cessation promotion at the workplace, deposit schemes are unpopular but very effective; therefore the current deposit scheme is designed to be the most attractive by having the largest potential total reward. In an attempt to maximise the effectiveness of incentive provision, participants receive automated advice regarding which scheme is most likely to fit their personal characteristics. This advice will be based on the following characteristics: 1. Degree of tobacco dependence. Based on the Fagerström Test for Nicotine Dependence.19 Fagerström score below 5 = no/low nicotine dependence, or Fagerström score of 5 or higher = nicotine dependent; 2. Readiness-to-quit. Based on Prochaska Stage of change.20 Preparation stage (readiness to quit within the next 30 days), or (pre-)contemplation stage (ready to quit within the next six months or not ready to quit at all);10, 20 Present bias. Measured by temporal discounting magnitude based on the Kirby scale.21 Temporal discounting refers to the phenomenon where future rewards are perceived as being worth less than an immediate reward.21 Based on a 27-item monetary choice questionnaire, those choosing more than 50% of the times the larger delayed rewards are classified as having delayed reward preference and those choosing less than 50% of the times the larger delayed rewards are classified as having present reward preference;21, 22
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