Behavioral Research Course

Behavioral Research: Lit Search 1b & c

[Second & third articles for Behavioral Research Lit Search 1 assignment — continuation of example]

Animals, including humans, tend to value the present more than the future. This time tax is called temporal discounting (a.k.a. delay discounting, future discounting, or time discounting). In other words, the longer we have to wait for a positive outcome the less positive it becomes.

We see this phenomenon in a number of behaviors. We spend money on brand new shoes at the expense of putting an extra $50 in our savings account. We enjoy just one more episode on netflix rather than working on homework. We eat a piece of chocolate cake (or in my case extra chocolate chip cookies) instead of the healthier snack. We indulge in a few too many adult beverages even though we know we’ll regret it tomorrow. We max out credit cards, smoke cigarettes, put off exercising, procrastinate, and purchase too little insurance. Our present self’s goals take precedence over our future self’s goals. When it comes to intertemporal choices, we put a tax on time.

This behavior varies across individuals. Why is it your roommate can put aside money every month? How is it your best friend can bounce out of bed every morning to go workout while you snuggle under the blankets?

The individual variability in our tendency to discount the future has always fascinated me. Much of my research focuses on this behavior and factors that relate to or can influence temporal discounting. In fact, we can liken discounting to an innate personality trait. But we also know that early life factors and situational variables can impact temporal discounting.

Recently, Bulley & Gullo (2017) investigated the impact of prospective thinking on discounting and alcohol demand. Problematic alcohol users, and substance abusers more generally, show steeper discount rates than non-problematic users. Therefore, incorporating both financial temporal discounting (in a more traditional measure of this behavior) and alcohol demand makes logical sense and provides added real world significance to this body work. The authors hypothesized that episodic future thinking would reduce discount rates and alcohol demand. In other words, they predicted that imagining the future would increase patience and decrease impulsivity.

Bulley & Gully (2017) invited 52 undergraduates to participant in their research study. The independent variable was imagery (episodic future thinking or control). In the episodic future thinking condition, participants imagined future events they were looking forward to at each of 5 delays (today, 2-days, 30-days, 180-days, and 363-days). These imagined events were used as cues during the intertemporal choice and alcohol purchase tasks. In the control imagery condition, the participants read two chapters of Pinocchio and events from this were used as cues for the tasks.

In the intertemporal choice task, participants made binary choices between a smaller, immediate monetary outcome and a larger, later monetary outcome. Before each choice, participants were cued with either a corresponding future event or an event from pinocchio.

The alcohol purchase task involves participants indicating how many drinks they would purchase and consume at various prices (without stockpiling). The prices were 1¢, 5¢, 13¢, 25¢, 50¢, $1, $2, $3, $4, $5, $6, $11, $35, $70, $140, $280, $560, & $1120.  Participants were presented with episodic (or control) cues throughout this task.

They used a within participants design (aka repeated measures design), meaning each participant completed the intertemporal choice task and alcohol purchase task twice, once following each condition (spaced a week apart).

Bulley & Gullo (2017) conducted a repeated measures ANCOVA with condition (episodic versus control) as the within-participants factor and discounting as the dependent variable.* The found that participants who engaged in the episodic future thinking discounted the future less than those in the control condition. They also found a small effect of episodic future thinking on alcohol demand intensity (i.e., how many drinks you’d purchase at 1¢).

Bulley & Gullo (2017) condluce that episodic future thinking plays a causal role in temporal discounting and, possibly, alcohol demand intensity.

In another study investigating factors that influenced temporal discounting, Lempert et al. (2016) investigated the effect of arousal on discounting. More specifically, they hypothesized that participants would show greater arousal when delayed options were framed in the context of a date (i.e., $20 on October 20) compared to a day (i.e., $20 in 30 days). They predicted that this increased arousal in the date condition would correspond to less discounting (in other words, more patience).

Participants (N=60 NYU students) were asked to respond to a series of binary choices between an immediate, smaller reward and a later, lager reward. The independent variable was framing (date, days – see above). The dependent variable was discount rate. While participants completed this task, they also measured pupil diameter to gauge arousal level, which served as a second DV. This study used a within participants design as participants both experienced the date and days condition.

Interestingly, Lempert et al. (2016) did not observe a difference in discount rates between the date and days condition (past research has shown increased patience when rewards are framed in terms of the date of receipt rather than days to receipt). They did find that pupil dilation was related to the subjective value of the delayed reward, suggesting that contextual emotion/affect could play a role in patience (in this case, the subjective value served as a predictor and pupil dilation was the outcome).

In other words, the results partially supported their hypothesis. They did observe a relationship between subjective value and pupil dilation, but this did not relate to the date/days manipulation. The authors caution, however, that these results are correlational (i.e., arousal was not manipulated) and therefore future research will be important to better understanding this relationship.

*the authors also included gender as a covariate

References

Bulley, A., & Gullo, M. J. (2017). The influence of episodic foresight on delay discounting and demand for alcoholAddictive Behaviors, 66, 1-6. https://doi.org/10.1016/j.addbeh.2016.11.003

Lempert, K. M., Johnson, E., & Phelps, E. A. (2016). Emotional arousal predicts intertemporal choiceEmotion, 16, 647-656. doi:  10.1037/emo0000168

 

 

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