The effects of percentile versus fixed criterion schedules on smoking with equal incentive magnitude for initial abstinence

Abstract

Incentives have been successfully used to reduce smoking in hard-to-treat (HTT) smokers by progressively reinforcing lower levels of breath carbon monoxide (CO). When compared with schedules only providing incentives for smoking abstinence, using a progressive (percentile) criterion facilitates longer periods of smoking abstinence. However, participants receiving incentives for lower breath CO levels on percentile schedules typically earn more for their first abstinent breath CO sample relative to participants receiving incentives only for smoking abstinence. Many studies show that larger incentive magnitude increases abstinence rates. The present study tested the effects of different incentive schedules on rates of abstinence maintenance while holding the initial incentive magnitude constant for 93 HTT smokers to eliminate initial abstinence incentive magnitude as a potential confound. Smokers were randomized to percentile, fixed criterion, or random incentive schedules. The incentive magnitude for the first abstinent breath CO sample (<3 ppm) was $5 for percentile and fixed criterion incentive participants, and then increased by $0.50 for each consecutive abstinent breath CO sample. All groups had similar patterns of meeting the abstinence criterion for at least 1 visit. However, once this abstinence criterion was met, abstinence was more likely to be maintained by fixed criterion incentive participants. Unlike previous studies comparing percentile and fixed criterion schedules, percentile incentive schedules were not associated with longer periods of abstinence relative to fixed criterion incentive schedules. Further studies that manipulate initial incentive magnitude are needed to test whether the difference between the current and previous studies was due to initial incentive magnitude.

Figure 1

Event records for percentile, fixed criterion and random incentive participants. An individual participant constitutes one row on the ordinate. Visit number is shown on the abscissa. Black areas represent visits with breath CO samples < 3 ppm. Gray areas represent visits with breath CO samples ≥ 3 ppm. White areas represent missed visits.

Figure 2

Proportion of participants who achieved at least a given number of consecutive breath CO samples < 3 ppm across each group. Open circles, closed circles and gray squares represent the percentile, fixed criterion, and random incentive groups, respectively.