Smokers, Smoking Deprivation, and Time Discounting

Abstract

This chapter investigates whether smokers exhibit greater time discounting than non-smokers, and how short-term nicotine deprivation affects time discounting. A unique feature of our experiment is that our subjects receive rewards not only of money, but also of actual tobacco. This is done in order to elicit smokers’ true preferences. Smokers are more impatient than non-smokers, consistent with previous studies. Additionally, nicotine deprivation makes smokers even more impatient. These results suggest that nicotine concentration has different effects on time preferences in the short and long runs.

The original article first appeared in the Journal of Socio-Economics 45:47–56, 2013. A newly written addendum has been added to this book chapter.

Appendix

1.1 A1. Definition of Variables Used in Regressions

Variable name	Explanation
D_SMOKER	Smoker dummy variable: 1 when subjects is smoker, 0 otherwise
D_DEPRIVATION	Deprivation dummy variable: 1 when subjects is nicotine deprived, 0 otherwise
DELAY	Time of earlier reward
D_DELAY_M2	Delay dummy variable in money session: 1 when delay is 1 week, 0 otherwise
D_DELAY_M3	Delay dummy variable in money session: 1 when delay is 2 weeks, 0 otherwise
D_DELAY_M4	Delay dummy variable in money session: 1 when delay is 3 weeks, 0 otherwise
D_DELAY_M5	Delay dummy variable in money session: 1 when delay is 4 weeks, 0 otherwise
D_DELAY_T2	Delay dummy variable in tobacco sessions: 1 when delay is 10 min, 0 otherwise in real tobacco session, 1 when delay is 1 h, 0 otherwise in hypothetical tobacco session
D_DELAY_T3	Delay dummy variable in tobacco sessions: 1 when delay is 20 min, 0 otherwise in real tobacco session, 1 when delay is 3 h, 0 otherwise in hypothetical tobacco session
D_DELAY_T4	Delay dummy variable in tobacco sessions: 1 when delay is 30 min, 0 otherwise in real tobacco session, 1 when delay is 12 h, 0 otherwise in hypothetical tobacco session
D_DELAY_T5	Delay dummy variable in tobacco sessions: 1 when delay is 40 min, 0 otherwise in real tobacco session, 1 when delay is 24 h, 0 otherwise in hypothetical tobacco session
AMOUNT	Amount of earlier rewards
D_AMOUNT_M2	Delay amount variable in money session: 1 when amount is 2,000 yen, 0 otherwise
D_AMOUNT_M3	Delay amount variable in money session: 1 when amount is 3,000 yen, 0 otherwise
D_AMOUNT_T2	Delay amount variable in tobacco sessions: 1 when amount is 2 puffs, 0 otherwise
D_AMOUNT_T3	Delay amount variable in tobacco sessions: 1 when amount is 0.5 cigarettes, 0 otherwise
D_AMOUNT_T4	Delay amount variable in tobacco sessions: 1 when amount is 1 cigarettes, 0 otherwise
D_AMOUNT_T5	Delay amount variable in tobacco sessions: 1 when amount is 1.5 cigarettes, 0 otherwise
RETURN	Return of later reward
D_RETURN_M4	Delay return variable in money session: 1 when return is 100 %, 0 otherwise

1. (continued)

Variable name	Explanation
D_RETURN_M5	Delay return variable in money session: 1 when return is 150 %, 0 otherwise
D_RETURN_M6	Delay return variable in money session: 1 when return is 200 %, 0 otherwise
D_RETURN_M7	Delay return variable in money session: 1 when return is 300 %, 0 otherwise

1.2 A2. Supplementary Data

Supplementary data associated with this chapter can be found, in the online version, at http://dx.doi.org/10.1016/j.socec.2013.4.005.

1.3 Addendum: Two Experiments Related to the Experiment in the Text

In this addendum, we introduce two experiments related to the experiment described in the text of this chapter. One is our future work, and the other is a past experiment that served as a foundation for this study.

1.4 B1. Neuroeconomics Experiment

It will be interesting to apply the present study to a neuroeconomics experiment. To define the brain areas and networks correlated with intertemporal choice is an important topic of neuroeconomics. For example, McClure et~al. (2004), using fMRI neuroimaging, found that two separate systems are involved in intertemporal decisions. One of these systems is comprised of the “beta areas,” which include the limbic and paralimbic cortical structures. McClure et~al. demonstrated that this structure is activated when people make intertemporal decisions, including decisions with immediate rewards. The other system is comprised of the “delta areas”, including the lateral prefrontal and parietal areas. This system is activated in response to choices that do or do not include immediate rewards. Kable and Glimcher (2007) also showed that the activities in the ventral striatum, medial prefrontal cortex and posterior cingulate cortex are positively correlated with the amount of rewards and negatively correlated with the delay. Both of the studies focused on general human behavior and did not focus on specific subject groups such as smokers. On the other hand, Peters et~al. (2011) and Luo et~al. (2010) found that the neural activity in the ventral striatum of smokers is significantly lower than that of non-smokers when faced with intertemporal choices that involve delay.

There are also some fMRI studies related to nicotine addiction, but these do not involve intertemporal choice. For example, Beaver et~al. (2011) separated subjects into two conditions after deprivation of smoking for 8 h. Their subjects were told to do a cognitive task after being administered either nicotine or placebo tablets. Beaver found that the activity of dopamine circuits such as the ventromedial prefrontal cortex and posterior cingulate cortex were significantly increased in the control group with the placebo tablet.

McClernon et~al. (2009) examined brain activity when smoking cues were showed to subjects who were under 24 h smoking deprivation. They found that the activities of brain areas related to visual sensory processing, attention, and action planning, such as the left occipital gyrus and the bilateral precuneus, were increased by smoking deprivation. In addition, they reported that the degree of pre-scan craving and the activation of the right dorsomedial prefrontal cortex were positively correlated.

To reveal the neurological basis of the influence of nicotine on intertemporal choice will be worthwhile work. Just like our present laboratory experiment, the neuroimaging work will be able to find the correlates of the effects of nicotine concentration in the long-run (by comparing smokers and non-smokers), and also in the short-run (by comparing deprived and non-deprived smokers). Furthermore, it may be possible to find different correlates in the different domains: money and tobacco. In our future neural experiment, we predict that the same areas as in the previous studies noted above will be activated by smoking deprivation, and we expect to find a neural foundation for the domain effects observed in our present behavioral experiment.

1.5 B2. Preliminary Experiment in Waseda University

We conducted an experiment in Waseda University prior to the present Osaka University experiment. In the Waseda experiment, we also had three sessions: real tobacco, hypothetical tobacco, and money. The basic setup in the Waseda experiment was quite similar to the one we used at Osaka University. However, an important difference was that we did not allow subjects to smoke during the resting time between the sessions. Since the experiment lasted about 3 h, we inadvertently imposed 3 h of smoking deprivation on the subjects in the non-deprived condition. Therefore, in the Waseda experiment, the “deprived” condition was a long-period deprivation condition, and the “non-deprived” condition was actually a short-period deprivation condition. Since this is not what we wanted to do, we reconstructed our experiment to solve this and other weaknesses (not reported here).

The details of experimental design are of paramount importance. Experimenters should examine them, considering all relevant possibilities. However, some problems are often not recognized until an experiment is actually conducted. Thus, preparatory experiments are usually extremely helpful to the eventual success of a study.