The influence of episodic foresight on delay discounting and demand for alcohol
Introduction
Making adaptive decisions often requires a decision-maker to suppress impulses towards immediate gratification in the pursuit of long-term goals. Difficulty doing so has been conceptualized as a key feature of impulsivity, and is characteristic of many behavioural disorders in which immediate gratification becomes highly prioritized over the pursuit of longer-term reinforcement (Bickel and Marsch, 2001, Gullo and Potenza, 2014, MacKillop et al., 2011). Thus, while there is a near-universal tendency to discount the value of future rewards relative to those in the here-and-now, individuals with substance abuse disorders, pathological gambling, obesity, and those who exhibit other risky health behaviours have been consistently found to more rapidly devalue rewards that are delayed in their receipt than healthy controls (Bickel and Marsch, 2001, Dixon et al., 2003, Story et al., 2014). For this reason, responses to intertemporal choices between rewards available immediately and those available only after a delay can act as a ‘behavioural marker’ of addiction-relevant outcomes including the severity, and risk of developing, dependence (for review see Bickel, Koffarnus, Moody, & Wilson, 2014).
Individual differences in discounting rate have been tied to a number of factors, including genetic heritability and early life developmental experiences (Anokhin et al., 2011, Mauro and Harris, 2000, Odum, 2011, Peters and Büchel, 2011). However, the rate at which future rewards are devalued can also vary widely within individuals, as a function of the perceived certainty of a future reward, the framing of the choice question, current affect, alongside other situational or biological variables (for reviews see Gray and Mackillop, 2015, Lempert and Phelps, 2015). One critical set of psychological variables associated with variation in the discounting rate is the manner in which individuals mentally represent or imagine future rewards and the context of their receipt (Bulley, Henry, & Suddendorf, 2016).
A number of recent experimental studies suggest that imagining the future, so-called episodic foresight (Suddendorf and Corballis, 1997, Suddendorf and Corballis, 2007) or episodic future thinking (Atance & O'Neill, 2001), can reduce the rate at which future rewards are discounted in the process of making intertemporal choices. In general, these studies have provided participants with modified intertemporal choice tasks (ICTs) in which a personally relevant future event cue is provided alongside the choice question (Benoit et al., 2011, Daniel et al., 2015, Daniel et al., 2013a, Daniel et al., 2013b, Kwan et al., 2015, Lin and Epstein, 2014, Liu et al., 2013, Palombo et al., 2014, Peters and Büchel, 2010). For example, in Peters and Büchel (2010), participants indicated their preference for either 20€ now, or 35€ in 45 days, while in some trials being simultaneously cued with an actual event they had planned in around 45 days time. In the episodic cue condition, preferences shifted towards longer-term rewards, and the strength of this effect was associated with individual differences in the vividness of mental imagery about the episodic future event.
The effect of episodic foresight has been shown to extend to real-world behavioural indices of impulsive choice. When tempted with unrestricted access to immediately gratifying, densely caloric food, both obese women and children consumed less if concurrently imagining personally relevant future events (Daniel et al., 2015, Daniel et al., 2013b). This effect of episodic foresight on impulsive eating has also recently been demonstrated in college women, such that food-related episodic future thinking led to more restricted consumption of freely and immediately available snacks (Dassen, Jansen, Nederkoorn, & Houben, 2016), and in a sample of obese or overweight women in a real-world food-court experiment (O'Neill, Daniel, & Epstein, 2015).
A large body of evidence suggests that problematic alcohol users tend to show steeper discounting rates than individuals who use alcohol at more moderate or less risky levels (MacKillop et al., 2011, Petry, 2001). While individuals may not be explicitly deciding between payoffs at different times when they choose whether or not to eat unhealthy foods or drink alcohol, there is commonality between the type of decision-processes tapped by the ICT, and the processes employed in such health-related consumption decisions (Yi, Mitchell, & Bickel, 2010). In both cases, the options exist to make either (i) a decision prioritizing immediate gratification (e.g. pleasure) or (ii) a decision that prioritizes longer-term gains (e.g. health). Purchase demand for alcohol is one measure than can be employed to investigate this decision-process, and is predictive of alcohol consumption (Dennhardt et al., 2015, Murphy et al., 2015) as well as problematic alcohol-related behaviours such as driving after drinking (Teeters, Pickover, Dennhardt, Martens, & Murphy, 2014).
Demand for alcohol can be directly assessed with hypothetical ‘alcohol purchase tasks’ (APTs) that ask participants to indicate their willingness to purchase hypothetical drinks at increasing costs (MacKillop et al., 2009, MacKillop et al., 2010, MacKillop and Murphy, 2007, Murphy et al., 2009). There is generally good correspondence between hypothetical tasks of this nature and tasks in which access to alcohol is provided (Amlung, Acker, Stojek, Murphy, & MacKillop, 2012). Given recent studies showing that episodic foresight can reduce not only delay discounting but also ‘impulsive’ eating, in the current study we aimed to explore the effect of episodic foresight on both standard monetary intertemporal choice, as well as alcohol demand using a hypothetical APT. Firstly, we hypothesized that engaging in episodic foresight during the ICT would attenuate the rate at which future rewards were subjectively devalued over time. Secondly, we hypothesized that engaging in episodic foresight would reduce ‘impulsive’ alcohol demand on the hypothetical APT.
Section snippets
Participants
Fifty-two undergraduate students participated in the study for course credit. The study was approved by the relevant university human research ethics committee. Four (7.7%) participants were excluded because they did not attend both experimental sessions. This left a final sample of 48 participants (33 females, 68.8%). The mean age of the sample was 20.67 years (SD = 5.36).
Design and procedure
Participants attended two sessions timed roughly one week apart. In both sessions, participants completed a modified ICT, in
Drinking behaviours of the sample
The mean AUDIT score was 5.73, with 14 (29%) participants scoring above the 8 + cut-off for hazardous drinking specified by Saunders et al. (1993). When asked how often they have a drink containing alcohol, approximately 17% of the sample responded with ‘never’, 38% with ‘monthly or less’, 31% with ‘2–4 times a month’, 13% with ‘2–3 times a week’ and 2% with ‘4 or more times a week’. When asked how many standard drinks they have on a typical day when they are drinking, approximately 56%
Discussion
This experiment investigated the impact of episodic foresight on intertemporal choices and alcohol demand. In line with our initial hypotheses, results demonstrated that imagining personally relevant future events during the monetary ICT attenuated the rate at which delayed rewards were discounted. Furthermore, cued episodic future thinking during the APT led to a small reduction in demand ‘intensity’ (demand at zero cost). However, contrary to our hypotheses, all alcohol demand indices aside
Role of funding source
MJG is supported by a National Health and Medical Research Council of Australia Early Career Fellowship (1036365).
Contributors
AB and MJG conceived the study. AB collected data and ran the analyses, with input from MJG. AB wrote the first draft of the paper, and MJG provided critical revisions. Both authors approved the final manuscript.
Conflict of interest
No conflict declared.
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