Perceived food palatability, blood glucose level and future discounting: Lack of evidence for blood glucose level's impact on reward discounting.

Some previous studies have shown that an increase in blood glucose level makes people more future oriented, however, results are inconsistent, other studies failing to replicate this effect. Here, we tested whether psychological factors (in this instance, perception of food pleasantness after consumption of more palatable or less palatable meal) can play a moderating role. We hypothesized that consuming more palatable food (perceived as rewarding) should cause blood glucose levels to affect future discounting, but that this should not occur for the consumption of less palatable food. A high-powered, independent groups experiment (N = 149, power ß = .90) showed that, subsequent to performing an initial discounting task, the two groups consuming a meal (a control group consumed no meal) displayed a significant increase in blood glucose levels 10 minutes after meal consumption and just before repeating the discounting task. However, the increased blood glucose levels did not cause changes in delay discounting in either experimental group.

Increasing blood glucose level via breakfast meals is not connected with changes in delay discounting.

Previous studies have revealed that increasing people's blood glucose level via drinking a soft drink containing sugar makes their financial decisions more future-oriented. This study extends these previous findings, testing whether the effect holds when blood glucose level is increased via intake of a normal meal (i.e., breakfast) rather than a sweet drink. Moreover, we test whether the size of the meal consumed (i.e., a normal vs. an oversized meal) can have a quantitatively different impact on levels of delay discounting. In two experiments using different time intervals between food consumption and discounting tasks (i.e., 60 min and 10 min), we successfully increased both blood glucose level and satiation level. Despite this, our results revealed that neither consumption of the meal itself nor the size of the meal influenced a preference for future rewards over present rewards. This suggests that satisfying hunger and increasing blood glucose level are not sufficient to make people more future-oriented.

Correction: Side Effects in Time Discounting Procedures: Fixed Alternatives Become the Reference Point.

[This corrects the article DOI: 10.1371/journal.pone.0165245.].

Side Effects in Time Discounting Procedures: Fixed Alternatives Become the Reference Point.

Typical research on intertemporal choice utilizes a two-alternative forced choice (2AFC) paradigm requiring participants to choose between a smaller sooner and larger later payoff. In the adjusting-amount procedure (AAP) one of the alternatives is fixed and the other is adjusted according to particular choices made by the participant. Such a method makes the alternatives unequal in status and is speculated to make the fixed alternative a reference point for choices, thereby affecting the decision made. The current study shows that fixing different alternatives in the AAP influences discount rates in intertemporal choices. Specifically, individuals' (N = 283) choices were affected to just the same extent by merely fixing an alternative as when choices were preceded by scenarios explicitly imposing reference points.

You Cannot be Partially Pregnant: A Comparison of Divisible and Nondivisible Outcomes in Delay and Probability Discounting Studies.

Research by The Psychological Record, 64(3), 433-440. doi:10.1007/s40732-014-0052-9, (2014) demonstrated the novel finding that the magnitude effect for medical outcomes does not reverse across delay and probability discounting as it does for monetary outcomes. We suggest that a possible reason for the lack of a reverse magnitude effect in nonmonetary outcomes is incomparable divisibility of discounted alternatives. To test whether the lack of a reverse magnitude effect in probability discounting of medical outcomes is due to incomparable divisibility of treatment effects, 4 studies were conducted. In the replication study, the effect observed by The Psychological Record, 64(3), 433-440. doi:10.1007/s40732-014-0052-9, (2014) was marginally not significant, although it was directionally consistent with their prediction of steeper discounting of small medical outcomes (as compared to large, defined as brain cancer) both in time and probability discounting. Our manipulation by substituting a divisible outcome (body paralysis) for an indivisible one (brain cancer) did not, however, bring expected results. We discuss the explanations and possible implications of introduced division for divisible and nondivisible medical outcomes.

Introducing conjoint analysis method into delayed lotteries studies: its validity and time stability are higher than in adjusting.

The delayed lotteries are much more common in everyday life than are pure lotteries. Usually, we need to wait to find out the outcome of the risky decision (e.g., investing in a stock market, engaging in a relationship). However, most research has studied the time discounting and probability discounting in isolation using the methodologies designed specifically to track changes in one parameter. Most commonly used method is adjusting, but its reported validity and time stability in research on discounting are suboptimal. The goal of this study was to introduce the novel method for analyzing delayed lotteries-conjoint analysis-which hypothetically is more suitable for analyzing individual preferences in this area. A set of two studies compared the conjoint analysis with adjusting. The results suggest that individual parameters of discounting strength estimated with conjoint have higher predictive value (Study 1 and 2), and they are more stable over time (Study 2) compared to adjusting. We discuss these findings, despite the exploratory character of reported studies, by suggesting that future research on delayed lotteries should be cross-validated using both methods.

Can taking the perspective of an expert debias human decisions? The case of risky and delayed gains.

In several previously reported studies, participants increased their normative correctness after being instructed to think hypothetically, specifically taking the perspective of an expert or researcher (Beatty and Thompson, 2012; Morsanyi and Handley, 2012). The goal of this paper was to investigate how this manipulation affects risky or delayed payoffs. In two studies, participants (n = 193) were tested online (in exchange for money) using the adjusting procedure. Individuals produced certain/immediate equivalents for risky/delayed gains. Participants in the control group were solving the problem from their own perspective, while participants in the experimental group were asked to imagine "what would a reliable and honest advisor advise them to do." Study 1 showed that when taking the perspective of an expert, participants in experimental group became more risk aversive compared to participants in the control group. Additionally, their certain equivalents diverged from the expected value to a greater extent. The results obtained from the experimental group in Study 2 suggest that participants became less impulsive, which means they tried to inhibit their preferences. This favors the explanation, which suggests that the perspective shift forced individuals to override their intuitions with the social norms. Individuals expect to be blamed for impatience or risk taking thus expected an expert to advise them to be more patient and risk aversive.

Affective and cognitive factors influencing sensitivity to probabilistic information.

In study 1 different groups of female students were randomly assigned to one of four probabilistic information formats. Five different levels of probability of a genetic disease in an unborn child were presented to participants (within-subject factor). After the presentation of the probability level, participants were requested to indicate the acceptable level of pain they would tolerate to avoid the disease (in their unborn child), their subjective evaluation of the disease risk, and their subjective evaluation of being worried by this risk. The results of study 1 confirmed the hypothesis that an experience-based probability format decreases the subjective sense of worry about the disease, thus, presumably, weakening the tendency to overrate the probability of rare events. Study 2 showed that for the emotionally laden stimuli, the experience-based probability format resulted in higher sensitivity to probability variations than other formats of probabilistic information. These advantages of the experience-based probability format are interpreted in terms of two systems of information processing: the rational deliberative versus the affective experiential and the principle of stimulus-response compatibility.