Psychlopedia -- Key concepts -- Cognitive concepts -- Temporal discounting
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Some people would prefer to receive $200 in one year than, for example, $100 now. In contrast, other people would prefer $100 now than $200 in one year; these individuals perceive the value of specific rewards to diminish rapidly over time. This sizeable preference towards more immediate rewards is sometimes described as an elevated level of delay or temporal discounting as well as an inability to delay gratification. In short, delay or temporal discounting refers to the extent to which individuals prefer immediate but modest rewards to future but sizeable rewards.
These elevated levels of discounting, or this inability to delay gratification, may underpin a host of psychological problems, such as gambling, substance abuse, depression, anxiety, anger, and many other psychological problems (e.g., Bickel & Marsch, 2001; Hoerger, Quirk, & Weed, 2011; Kirby, Petry, & Bickel, 1999). Similarly, this inclination to prefer immediate rewards rather than future rewards is associated with unsatisfactory academic performance (Kirby, Winston, & Santiesteban, 2005). Finally, this inclination towards immediate rewards is negatively related to social attributes, such as agreeableness (Miller et al., 2008) and empathy (Kirby et al., 1999).
Many interventions and changes can also curb this tendency and thus resolve these problems. For example, the elimination of injustices or inequalities in income, as well as the removal of fast food icons, tend to overrides these concerns.
Determinants of temporal discounting
Justice and deprivation
If individuals feel they have not received the outcomes they deserve in life, and thus feel resentful and dissatisfied, they do not feel their pursuits or endeavors will be rewarded in the future. Consequently, they do not commit to enduring aspirations but instead focus on their more immediate needs. They are, therefore, more inclined to value immediate rewards over future rewards. That is, they tend to demonstrate delay discounting, increasing the likelihood of various problems such as gambling.
This set of propositions was proposed and validated by Callan, Shead, and Olson (2011). In their first study, participants completed some questionnaires about their income and spending. Their answers were supposedly subjected to an algorithm that will calculate their discretionary income relative to other people. Some participants were informed their discretionary income-?that is, the amount they can spend after purchasing mandatory goods such as food-?is significantly lower than peers. This information was intended to evoke resentment and dissatisfaction with their wealth. Other participants were informed their discretionary income slightly exceeds average.
Next, participants completed a measure of delay discounting. That is, they were asked whether they prefer a certain amount of money, such as $250 now, or more money, such as $500, one, seven, 30, 90, 180, 365, or 730 days later. In general, if participants were told their discretionary income was low, they tended to prefer some money now rather than more money later. That is, they preferred immediate rewards over future possibilities. A subsequent study showed this preference towards immediate rewards increases the propensity of people to gamble. For example, if participants tended to prefer some money now rather than more money later, they were more inclined to purchase lottery tickets. They seek an abrupt reward now rather than feel motivated to toil assiduously over a long time.
A third study confirmed this relationship. Specifically, some participants were exposed to an article entitled "Good things come to those who live in the moment: Research highlights the importance of living in the here-and-now". This article prompted individuals to value immediate rewards over future possibilities. Other participants were exposed to an article entitled "Good things come to those who wait: Research highlights the importance of patience". This article prompted individuals to value future possibilities over immediate rewards. Again, when the preference towards immediate rewards was amplified, participants were more willing to purchase lottery tickets.
In the final study, participants completed a survey. The survey assessed the extent to which individuals feel they have not received the outcomes they deserve in life, called personal relative deprivation. The survey also assessed whether individuals prefer small immediate rewards over larger future rewards. Finally, the survey gauged the propensity of individuals to gamble. A position association between personal relative deprivation and gambling was uncovered. This association was mediated by delay discounting--that is, the inclination of individuals to prefer immediate rewards over future rewards.
Opportunities to confirm the world is just
Similarly, people like to assume the world is fair and just. That is, they want to believe that individuals receive the rewards and recognition they deserve. Consequently, they want to believe that victims deserve their misfortune, called the just world bias.
If the world does not seem fair and just, individuals may not feel their attempts to achieve some future goal may be rewarded. They may not be as willing to sacrifice their immediate needs to pursue some future aspiration. That is, the inclination to delay gratification may diminish, exacerbating temporal discounting.
This possibility was proposed and validated by Callan, Harvey, and Sutton (2014). In one study, participants read about a person who was the victim of a crime or misfortune. Next, to prime a belief in a just world, some participants were informed this victim was a drug dealer and, therefore, in some sense deserved this misfortune. Other participants did not receive this information. Finally, the extent to which participants prefer small rewards now to larger rewards in the future was assessed. If the belief in a just world had been primed, because the victim was a drug dealer, temporal discounting diminished: Participants were more inclined to prefer larger rewards in the future to smaller rewards now.
As Li, Li, and Liu (2011) showed, after people hear about a nearby tragedy, they are more likely to delay future gains and perhaps future losses. That is, they are especially likely to prefer moderate rewards now over larger rewards in the future. Presumably, after major catastrophes, people feel their life is vulnerable. They do not feel as connected to the future and instead overestimate the importance of their immediate needs.
In this study, just over 100 individuals completed an instrument six months before and two months after an earthquake of magnitude 8.0 on the Richter scale in Wenchuan, China during 2008. The participants lived in Beijing, about 2000 km away. They received a series of questions, such as whether they prefer 100 yuan now or 120 yuan in one year as well as whether they prefer to lose $1000 yuan now or lose yuan $2000 in one year. After the earthquake, delay discounting increased. That is, participants were especially likely to prefer a moderate amount now than a larger amount later.
Cues associated with impulsivity
In one study, reported by Zhong and DeVoe (2010), some participants were exposed to subliminal pictures of fast food logos, like KFC, Taco Bell, and Burger King. Exposure to these logos was shown to expedite the rate at which participants read an extract. In a subsequent study, these logos increased the likelihood that individuals would purchase products that conserve time--such as a 2 in 1 shampoo. The final study showed these logos also increased temporal discounting: That is, participants often preferred smaller rewards now than larger rewards in the future.
According to Zhong and DeVoe (2010), individuals associate fast food with impatience. Fast food enables individuals to consume food rapidly and, thus, is associated with haste and impatience rather than a willingness to wait. Exposure to fast food, hence, elicits an inclination towards impatience.
Gains versus losses
Researchers have examined whether gains or losses are discounted more rapidly over time. Some evidence indicates that losses or problems are discounted more heavily than gains or benefits.
To illustrate, in one study, conducted by Highhouse, Mohammed, and Hoffman (2002), participants read about potential opportunities or threats that could affect some hypothetical company. Although more immediate opportunities and immediate threats were perceived as equally likely and consequential, future opportunities were perceived as more likely and consequential than future threats. That is, the perceived likelihood and gravity of threats, but not opportunities, diminished rapidly over time.
Arguably, when people contemplate the distant future, they are more concerned with overarching values and benefits, instead of specific problems and complications. Therefore, as they orient their attention to the future, people are not as concerned about losses or threats.
After men observe attractive women, impulsive behavior and temporal discounting becomes more pronounced. For example, in one study, conducted by Wilson and Daly (2004), some male participants were instructed to evaluate the appearance of various photographs of attractive women. Other male participants were instructed to evaluate the appearance of various photographs of unattractive women. Next, they undertook a task that gauges temporal discounting. After observing attractive women, rather than unattractive women, the participants were more inclined to prefer immediate rewards over more sizable returns in the future. This impact of attractive females is especially pronounced in men who are sensitive to rewards (van den Bergh, Dewitte, & Warlop, 2008).
Attractive women might increase testosterone levels in men (Ronay & von Hippel, 2010). This testosterone evokes a sense of aggression or urgency that translates to a preference towards immediate rewards.
In contrast to other negative emotions, such as disgust, individuals who feel sadness prefer a modest amount of money now to appreciably more money three months later. That is, sadness seems to amplify temporal discounting (Lerner, Li, & Weber, 2013).
In one study, to evoke sadness, participants watched a video clip about the death of a boy's mentor. To evoke disgust, other participants watched a video clip about an unsanitary toilet. In the control condition, participants watched a clip about the Great Barrier Reef. Next, all participants wrote an essay about a time that evoked the same emotion. Next, they were asked to indicate the extent to which they prefer immediate but modest rewards over larger but delayed rewards--and 1 in 13 participants actually received these rewards. Relative to the other individuals, sad participants were more likely to prefer immediate but modest rewards over larger but delayed rewards.
The second study was similar. However, participants were also instructed to type their thoughts about each choice. Later, they were asked to indicate which of the two options each thought favored. According to query theory, the first thoughts or queries tend to more influential than subsequent thoughts or queries. Indeed, in this study, when participants were sad, their earlier thoughts were more likely to support the choice of immediate rewards than did their later thoughts. The final study showed that sadness increases temporal discounting only when people need to decide between an immediate reward and a delayed reward rather than two delayed rewards at different times.
Whereas sadness tends to amplify temporal discounting, feelings of gratification in particular, rather than happiness in general, tend to curb temporal discounting (DeSteno, Li, Dickens, & Lerner, 2014). In one study, for example, reported by DeSteno, Li, Dickens, and Lerner (2014), participants were instructed to recall and write about an event that had evoked gratitude, happiness, or neutral emotions, such as a typical day. Next, participants needed to decide which of various choices they would prefer, such as $11 now or $25 in one month. To motivate participants, individuals were informed that some participants would actually be granted this money. Relative to the other conditions, gratitude increased the degree to which participants were willing to delay gratification and choose a larger reward in the future instead of a lesser reward now.
Arguably, gratitude evolved to facilitate reciprocal altruism. In particular, communities can thrive only if individuals who receive assistance from someone now will reciprocate this help in the future. Gratitude may have been the emotion that evolved to motivate this reciprocity in the future. Therefore, people tend to associate gratitude with delayed gratification: the notion that helpful acts now will and should be rewarded in the future. Gratitude, therefore, should prime delayed gratification and reduce temporal discounting.
Blood glucose tends to curb discounting. That is, as discovered by Wang and Dvorak (2010), after individuals consumed a drink with glucose rather than an artificial sweetener, they become more likely to delay gratification. They were especially likely to prefer sizeable rewards in the future than moderate rewards now. This finding is consistent with the premise that blood glucose underpins self control and curbs ego depletion or mental exhuastion.
A less concrete construal of future events
According to Kim, Schnall, and White (2013), temporal discounting can be ascribed to the haziness of future rewards or punishments. That is, in general, according to construal level theory, whenever people contemplate more immediate events, their attention is oriented towards specific details and features. Immediate rewards and punishments, therefore, seem more vivid and certain.
In contrast, when people contemplate future events, their attention is often oriented towards intangible patterns or broad categories instead of specific details and features. Future rewards and punishments seem hazier rather than vivid and certain. Consequently, these future rewards and punishments do not evoke strong emotional reactions and, therefore, seem less important, culminating in temporal discounting.
If this argument is correct, manipulations of construal should override temporal discounting. This possibility was confirmed by Kim, Schnall, and White (2013) in a series of studies. In the control condition of the first study, participants needed to decide whether they prefer a small monetary reward now over a larger monetary reward in the future. For example, on one trial, participants decided whether they prefer $300 now or $500 in one year. In the other condition, however, the alternatives were vouchers to specific hotels and trips. For instance, on one trial, participants decided whether they prefer a $300 voucher for a 3 star hotel in Paris now or a $500 voucher for a star hotel in Paris in a year. The options were also accompanied by vivid photographs. Temporal discounting diminished when the options referred to specific hotels and trips.
A subsequent set of studies confirmed and extended this premise. For example, the same results were observed when the alternatives related to renowned sites, such as the Eiffel Tower, and photographs were excluded. Therefore, the photographs themselves are not responsible for this pattern of observations. In addition, when the alternatives related to Paris, but details were excluded, temporal discounting was reinstated, as hypothesized. Furthermore, when people needed to reach a choice for strangers--known to provoke an abstract construal--temporal discounting also diminished; this manipulation, presumably, evoked an abstract construal for both immediate and future rewards. Hence, both the immediate and future rewards were equally fuzzy.
Episodic future thinking
Some variants of future consideration have been shown to diminish temporal discounting and inspire people who are overweight or obese to refrain from excessive food intake. Specifically, Daniel, Stanton, and Epstein (2013) showed that a specific technique, called episodic future thinking, may contain impulsive behavior and curb overeating.
In this study, some participants imagined desirable events that might unfold in 1 day, 2 days, 1 week, 2 weeks, 1 month, 6 months, and 2 years. Next, they described these events, and these descriptions were audio recorded. In the control condition, participants merely described entries of a travel blog, written by someone else. Next, participants completed a temporal discounting task. They were asked whether they would prefer, for example, $10 now or $100 in 1 day, 2 days, 1 week, 2 weeks, 1 month, 6 months, and 2 years. While completing this task, their previous description associated with time period was replayed, and they were asked to imagine this event. Finally, the participants, all of whom were overweight or obese, were granted access to unlimited unhealthy food.
If participants imagined hypothetical future events, temporal discounting decreased. That is, participants were more likely to choose a higher reward in the future than a modest reward now. They were also more likely to refrain from eating the unhealthy food.
Correlates of temporal discounting
Working memory, executive functioning, and intelligence
Elevated levels of temporal discounting might sometimes represent impairments in working memory. Specifically, when working memory is impaired, individuals may not be able to maintain their attention on hypothetical, but plausible, future consequences. Consistent with this proposition, if working memory is distracted by other considerations, temporal discounting is amplified (e.g., Hinson, Jameson, & Whitney, 2003; Hinson, Jameson, & Whitney, 2003; for some controversies about these principles, see Franco-Watkins, Rickard, & Pashler, 2010).
Furthermore, intelligence, which is correlated with working memory capacity, has been shown to be negatively associated with temporal discounting. A meta-analysis, undertaken by Shamosh and Gray (2008), showed the correlation between intelligence and temporal discounting was -.23. That is, intelligent people were significantly more likely to prefer small rewards now than larger rewards in the future.
Weatherly and Ferraro (2011) showed that executive functioning is also inversely associated with temporal discounting. Participants completed a questionnaire that gauges five facets of executive or prefrontal functioning: drive, impulsive control, empathy, organization, and planning. Apart from impulse control, all of these facets were correlated with various measures of temporal discounting. For example, if planning was impaired, smokers were especially likely to prefer a few cigarettes now to more cigarettes later. If empathy was impaired, individuals were more inclined to settle with a reasonable partner now than a better partner in the future.
The relationship between personality and temporal discounting depends on cognitive ability. Specifically, when cognitive ability is impaired, extraversion is positively associated with temporal discounting: That is, extraverts are especially likely to value modest rewards now over larger gains in the future. In contrast, when cognitive ability is elevated, neuroticism rather than extraversion is positively related to temporal discounting, as shown by Hirsh, Morisano, and Peterson (2008).
Presumably, when individuals are extraverted, they are more sensitive to positive emotions. Hence, the urges to choose immediate rewards are amplified. Nevertheless, if cognitive ability is elevated, individuals tend to exhibit more self control and can, thus, override these powerful urges more effectively. Therefore, if individuals are intelligent, extraversion does not translate to an inclination to choose immediate rewards over future rewards.
Nevertheless, this capacity to control urges, which correlates with cognitive ability, is impaired by anxiety. Neuroticism and anxiety, thus, will undermine the benefits of cognitive ability. Accordingly, when cognitive ability is elevated, neuroticism will tend to undermine the delay of gratification.
Mahalingam, Stillwell, Kosinski, Rust, and Kogan (2013) also examined the relationship between personality, as gauged by the five factor model, and temporal discounting. To assess personality, participants completed the International Personality Item Pool, comprising 100 items. In general, if participants exhibited limited openness and conscientiousness, but pronounced extraversion and neuroticism, they were especially inclined to prefer modest rewards now over larger rewards in the future. The effects of openness and neuroticism were magnified whenever the rewards were larger.
Arguably, if people are impulsive and impatient, they are not as inclined to explore novel possibilities and hence their openness declines. The strong emotions that neuroticism and extraversion provoke could diminish the capacity of individuals to delay gratification.
Digit ratio reflects the extent to which the ring finger is longer than is the index finger. A long ring finger tends to coincide with elevated levels of testosterone before birth and aggression later in life. Research indicates that a long ring finger, relative to the index finger, also corresponds to a preference towards immediate, rather than future, financial rewards. However, this association has been observed in women but not in men (Lucas & Koff, 2010).
Green, Fry, and Myerson (1994) examined whether or not temporal discounting varies across age. Children, young adults, and older adults completed a temporal discounting task. The children were the most likely to value small monetary rewards now over larger monetary rewards in the future. The older adults were the least like to value small monetary rewards now over sizeable monetary rewards in the future.
At first glance, these findings seem to contradict the socioemotional selectivity theory. According to this theory, older individuals tend to value positive emotions and social interactions over future growth in knowledge and resources. In this sense, older individuals are more impulsive. Nevertheless, Green, Fry, and Myerson (1994) showed that older adults do not value immediate monetary rewards rather than other forms of reward. Perhaps older adults, because of their inclination to seek positive emotions and engage in social interactions, do not value small monetary rewards at all. However, they may value large monetary rewards in the future, because such finances could help their descendants.
Consequences of temporal discounting and correlates with wellbeing
Problems with inhibition
Many psychological problems are ascribed to an inability of people to inhibit urges. That is, to function effectively, individuals need to inhibit temptations now to improve their life in the future. Problems with alcohol and illicit drugs as well as conduct disorder and antisocial behavior have all been ascribed to this mechanism. Consistent with this premise, all of these problems also correlate with elevated levels of temporal discounting, as shown by Bobova, Finn, Rickert, and Lucas (2009).
Similarly, Bickel, Odum, and Madden (1999) showed that smoking is related to temporal discounting. Specifically, in this study, participants completed the titration method to determine whether they prefer immediate rewards now or more sizeable rewards later. In general, smokers were more inclined to value immediate rewards now over more sizeable rewards later relative to non-smokers or ex-smokers.
Temporal discounting is also related to ADHD, a disorder that corresponds to an impaired ability to control impulses. That is, in a study conducted by Hurst, Kepley, McCalla, and Livermore (2011), participants complete a temporal discounting task, in which they needed to decide between small returns now and larger rewards in the future. In addition, they completed a questionnaire that assesses symptoms of ADHD. Individuals who reported symptoms of ADHD were more inclined to prefer the small returns now over larger returns in the future.
Temporal discounting is also associated with the likelihood that people will commit a criminal offence, at least in adulthood. That is, if individuals value immediate rewards over larger future rewards, they are more likely to perpetrate a crime or offence (Hanoch, Rolison, & Gummerum, 2013).
This possibility was uncovered by Hanoch, Rolison, and Gummerum (2013). In this study, people completed a measure that gauges the degree to which they prefer immediate monetary rewards to large future rewards. Some of the participants were ex-prisoners or current prisoners. Other participants had never been imprisoned. People who had been imprisoned were more likely to discount larger rewards. That is, they often preferred immediate rewards over very large rewards in the more distant future. Presumably, if people discount future rewards, they are not motivated enough to develop their capabilities gradually but are motivated to seek immediate rewards.
Temporal discounting also seems to correlate with indices of stress. In one study, conducted by Diller, Saunders, and Anderson (2008), participants completed a temporal discounting task. In addition, their heart rate was measured before and during an arithmetic task.
If participants tend to prefer smaller rewards now than larger rewards later--and thus exhibit an elevated rate of discounting over time--their heart rate increased to a greater extent while completing the arithmetic task. These findings imply that impaired delays in gratification may correlate with an increased sensitivity to stress. These individuals, perhaps, are more concerned about their immediate states than future possibilities. They are, consequently, more sensitive to problems that unfold now rather than problems that might unfold in the future.
Mechanisms that underpin temporal discounting
The CAPS model
Individuals often need to suppress or restrain their immediate temptations, impulses, urges, and emotions to earn future rewards. They might, for example, need to inhibit their motivation to sleep and study for an exam. They might need to inhibit their desire to eat a marshmallow now, even if told they can receive two marshmallows later if they delay their consumption, called the marshmallow test (Mischel, Shoda, & Rodriguez, 1992). This capacity is called delayed or deferred gratification and is highly correlated to consideration of future consequences (Strathman, Gleicher, Boninger, & Edwards, 1994).
Several models have been proposed to explain the mechanisms that underpin delayed gratification; these models, thus, should be applicable to consideration of future consequences as well. One theory was proposed by Mischel and Ayduk (2002), and derived from the cognitive-affective personality systems (CAPS) model (Mischel & Shoda, 1995). The CAPS model, as delineated by Mischel and Shoda (1995), conceptualizes personality as a network of units that represent potential cognitive or affective responses, each activated by cues in the environment. These units represent personal goals, expectations, beliefs, emotions, standards, competencies, intentions, and strategies, derived from biological substrates and social learning.
Some of the units revolve around strategies to regulate behavior and control attention. Specifically, the capacity to inhibit intense, but undesirable, temptations or impulses depends on two key inclinations: the motivation to regulate behavior and the capacity to regulate behavior. Motivation to regulate behavior depends on the appraisal that an act is unsuitable, beliefs about the consequences of this act, as well as the desire to maintain desirable behavior. Capacity to regulate behavior, however, depends on the accessibility or salience of units that underpin this inhibition of unsuitable behavior.
Interestingly, many cues can affect the accessibility of these units and, thus, ultimately shape delay in gratification. Specifically, cues that relate to abstract, rational concepts, called cool qualities, like "Think about the marshmallow as a cloud", tend to delay gratification. Cues that relate to sensations and rewards, such as "While you wait, think about cookies", called hot qualities, curbs this delay. These findings imply the cognitive-affective units can be classified into two systems: an emotional, hot system, partly underpinned by the amygdala, and a cognitive, cool system, more related to the hippocampus (Metcalfe & Mischel, 1999; for a similar distinction, see Cognitive experiential self theory). As stress escalates, the hot system tends to dominate the cold system; to regulate impulses the mechanisms that attenuate the intensity of the hot system need to be activated.
The capacity to apply suitable strategies and thus delay gratification as a toddler, perhaps by distracting their attention to toys or other people, predicts this capacity later in life (see Sethi, Mischel, Aber, Shoda, & Rodriguez, 2000). To illustrate, some toddlers can distract their attention to the experimenter or other objects when their parents leave the room. This tendency predicts the capacity of individuals to delay gratification later in life. Furthermore, these strategies, later in life, are inversely related to both aggression (e.g., Rodriguez, Shoda, Mischel, & Wright, 1989) and sensitivity to rejection (Levy, Ayduk, Downey, 2001).
Nevertheless, the children who delay gratification most effectively seem to orient their attention initially to hot cues and then shift to cold cues (Peake, Hebl, & Mischel, 2002). Conceivably, this tendency enables individuals to develop the capacity to demonstrate flexibility in whether they inhibit or subject themselves to the hot system. If individual always inhibit the hot system, many of their core needs will never be fulfilled.
Hot systems, cold systems, and personality
To some extent, as Hirsh, Guindon, Morisano, and Peterson (2010) reviewed, delay discounting partly depends on the relative activation of two distinct systems, called hot and cool processes, as defined by Metcalfe and Miscel (1999). Sometimes, the decisions and behaviors of individuals are primarily governed by powerful emotional forces, called hot processes, partly underpinned by the mesolimbic dopamine system. On other occasions, the decisions and behaviors of individuals are primarily dictated by more deliberate processes and conscious goals, called the cool system, primarily underpinned by the frontal or parietal cortices, especially the anterior prefrontal cortex. When hot processes override cool processes, immediate rewards are more likely to govern behavior, manifesting as delay discounting.
Extraverted individuals are likely to demonstrate elevated levels of delay discounting. That is, the dopaminergic system is especially sensitive in extraverted individuals. To clarify, the prospect of rewards is particular likely to govern the behavior of extraverted individuals. Accordingly, the hot system often dominates in extraverted people, translating to elevated levels of delay discounting (Hirsh, Guindon, Morisano, & Peterson, 2010).
This hypothesis was confirmed by Hirsh, Guindon, Morisano, and Peterson (2010). First, delay discounting was assessed. Participants had to decide whether they would prefer a large amount, such as $1000, or a smaller amount, such as $20 after some delay like one week. They completed 114 of these choices. These choices were then subjected to a formula, called a hyperbolic discounting rate, to estimate the discounting rate. A high discounting rate reflects a preference towards immediate rewards over future rewards. Admittedly, these choices were contrived, because participants did not actually receive the money. However, contrived and actual decisions seem to generate similar patterns of observations (e.g., Lagorio & Madden, 2005). This discounting rate was positively associated with extraversion.
Neurological mechanisms that underpin temporal discounting
The dual component model
A dual component model of temporal discounting was promulgated by McClure, Laibson, Loewenstein, and Cohen (2004; see also McClure, Ericson, Laibson, Loewenstein, Cohen, 2007). First, according to this model, mesolimbic regions like the nucleus accumbens and medial prefrontal cortex are activated when individuals choose alternatives that confer immediate rewards. The nucleus accumbens and medial prefrontal cortex represent part of the mesolimbic pathway; in this pathway, dopaminergic neurons project from the midbrain, specifically the ventral tegmental area, to regions like the amygdala, hippocampus, nucleus accumbens, and medial prefrontal cortex.
Second, lateral cortical regions, especially the dorsolateral prefrontal cortex and posterior parietal cortex, are activated when individuals consider choices that could confer either immediate or future rewards. McClure, Laibson, Loewenstein, and Cohen (2004) referred to the mesolimbic and lateral cortical regions as the beta and delta systems respectively. They argued the beta system increases the weight of immediate rewards and the delta system increases the weight of rewards at other times as well. From this perspective, limited levels of temporal discounting, and thus consideration of future consequences, might represent elevated activation of the lateral cortical regions relative to the mesolimbic regions.
Nevertheless, as Kable and Glimcher (2007) argued, temporal discounting could be underpinned by the mesolimbic region alone. Specifically, activation of this region diminishes if rewards are either delayed or limited in magnitude. They maintain this system alone represents the significance of a reward, by integrating information about both the time and magnitude, applying hyperbolic discounting.
To reconcile this conflict, Ballard and Knutson (2009) utilized fMRI to examine the activation of various regions in the aftermath of immediate or delayed rewards at various magnitudes. The findings were telling. First, as the magnitude of future rewards increased, activation of the mesolimbic regions, including the nucleus accumbens, medial prefrontal cortex, and posterior cingulate cortex, also escalated. These regions thus represent the magnitude of delayed rewards. Second, as the delay of future rewards increased, lateral cortical regions, including the dorsolateral prefrontal cortex, posterior parietal cortex, and temporal-parietal junction, diminished--especially in impulsive participants who discounted future rewards. Furthermore, some regions, like the medial prefrontal cortex and posterior cingulate cortex, but not the nuclear accumbens, were sensitive to both the delay and magnitude of the rewards, particularly in impulsive participants. These findings corroborate the notion that two distinct systems might underpin temporal discounting, but also emphasize that even the mesolimbic system is sensitive to future rewards.
These results are consistent with the proposition that inhibiting immediate gratification, and instead choosing a course of action that confers a sizeable reward in the future, demands cognitive control and inhibition of dominant inclinations. This inhibition, potentially underpinning self control, demands the dorsolateral prefrontal cortex, posterior parietal cortex, and also perhaps the inferior frontal gyrus--which was also contingent upon both delay and magnitude. Presumably, this inhibition is more difficult to maintain over longer durations, explaining the finding that activation of these regions decreases as the delays increase, especially in impulsive individuals.
Regions associated with intelligence
Shamosh, DeYoung, Green, Reis, Johnson, Conway, and Gray (2008) showed that regions associated with general intelligence could also underpin delay discounting. In this study, participants completed a task that assesses the extent to which they discount delayed rewards. In addition, participants undertook Raven?s Advanced Progressive Matrices to assess their general intelligence. Finally, fMRI imaging was utilized to gauge neural activity while the participants completed another task, intended to assess working memory. When intelligence was elevated, delay discounting diminished. This relationship was partly mediated by activation of the left anterior prefrontal cortex, a region that is assumed to integrate a variety of subtasks to pursue a broader goal (Koechlin & Hyafil, 2007).
Delay gratification in people who consume excessive alcohol
Claus, Kiehl, and Hutchison (2011) also examined the neural regions that are activated, using fMRI, while individuals need to choose between small returns now and larger returns in the future. Specifically, these researchers examined whether or not the neural regions that were activated differ between participants who consume excessive alcohol and participants who consume limited alcohol.
If participants reported elevated consumption of alcohol, this task increased activation of several regions, including the insular cortex, the inferior frontal gyrus, the rostral section of the anterior cingulate cortex, and the precuneus. Activation of the insula may imply that delayed gratification elicits stronger negative emotions in people who consume excessive alcohol. Activation of the inferior frontal gyrus may indicate these individuals cannot as readily withhold urges or select between alternative responses. Activation of the rostral anterior cingulate cortex may imply these decisions elicit a greater sense of conflict in people who drink considerable alcohol. Finally, activation of the precuneus might indicate these individuals are more aware of their personal interests instead of the needs of other people.
Activation of the caudate nucleus, which together with the putamen constitutes the dorsal striatum, might also affect temporal discounting. Specifically, in one study, conducted by Onoda et al. (2011), participants completed a measure of temporal discounting while neural activation was monitored. Interestingly, if participants greatly valued small returns now over larger returns in the future, the dorsal region of the caudate was more likely to be activated. If participants were able to delay gratification instead, valuing future rewards, the ventral region of the caudate was more likely to be activated.
Measures of temporal discounting
Two main approaches can be used to measure temporal discounting: behavioral measures and self report measures. To illustrate a behavioral measure, individuals are often asked to choose between an array of options. For example, they might be asked whether they would prefer $100 now or $150 in 6 months. Then, participants might be asked whether they would prefer $200 now or $250 in 1 year. After a series of these questions, a formula is used to estimate the extent to which the perceived value of rewards diminishes over time.
To illustrate a self report measure, participants might receive a series of questions that gauge discounting. One of these questionnaires was developed by Hoerger, Quirk, and Weed (2011). This questionnaire comprises 35 items and entails five facets of discounting. Specifically, individuals are asked the extent to which they can resist immediate temptations in the domain of food (e.g., "I can resist junk food when I want to"), physical pleasure (e.g., "I am able to control my physical desires"), social interaction (e.g., "I hate having to take turns with other people", reverse scored), money (e.g., "It is hard for me to resist buying things I can't afford", reverse scored), and achievement (e.g., "I worked hard in school to improve myself as a person").
This measure of discounting or delay gratification was correlated with many other relevant scales. Unsurprisingly, when participants reported a willingness to delay gratification, they were more conscientious and exhibited elevated levels of self control and self discipline as well as openness to experience. Furthermore, they also reported higher levels of health, exercise, and wellbeing. In the social domain, they were more agreeable and altruistic. Finally, they reported fewer symptoms of depression, anxiety, anger, and externalizing problems.
The titration method
One example of a behavioral discounting task is the titration method, undertaken for instance by Bickel, Odum, and Madden (1999). Participants are first asked whether they prefer $1000 now to $1000 in one week. Almost all participants prefer $1000 now. The experimenter then changes the first amount to $990. That is, participants are asked whether they prefer $990 now to $1000 in one week. The experimenter then continues to reduce the first amount to $960, $920, $850, $800, $750, and so forth until the participant no longer prefers the immediate amount. The entire process is then repeated for 6 other delays: 2 weeks, 1 month, 6 months, 1 year, 5 years, and 25 years.
Exponential versus hyperbolic formulas
Two forms of temporal discounting have been differentiated: exponential and hyperbolic (see Ainslie, 2001, 2006). According to exponential discounting, the value of some reward diminishes proportionately with time. If $100 today is equivalent to $200 in one week, then $100 today is also equivalent to $300 in two weeks. According to hyperbolic discounting, a similar function underpins the decline in value over time. However, initially, the value does not diminish as steeply over time as does exponential discounting. After some particular time, the value then begins to diminish more steeply. Hyperbolic discounting arises because individuals sometimes value future rewards more than anticipated. They might, for example, perceive future rewards as diagnostic of immediate decisions--hence, they perceive these future events as psychologically close in time.
Other formulas to model inter-temporal choice
Typically, in economics, a formula called hyperbolic temporal discounting is applied to model inter-temporal choices, in which individuals need to decide between a small amount of money sooner and a larger amount of money later. Ericson, White, Laibson, and Cohen (2015) developed a model, called the inter-temporal choice heuristic model or ITCH model, that seems to correspond to the choices that individuals reach more accurately than previous models.
The ITCH model incorporates four key assumptions. First, to compare two options, individuals apply both subtraction to reflect relative difference and division to reflect absolute difference. Second, each option is also compared to a reference point. Third, the monetary and time dimensions are compared independently of one another. Finally, the results of all these comparisons are aggregated, but weighted with coefficients. This model generates a simple equation with four terms: money and time multiplied by absolute and relative. The model predicts actual effects of delays in both the immediate and future options effectively.
Dixon and Cummings (2001) designed an intervention that is intended to curb temporal discounting. This intervention was successfully applied to several children diagnosed with autism.
In this study, children were granted a choice between a small and large item, such as a small and large bag of popcorn. Specifically, they were asked whether they want the small item now or the large item after waiting a while. This task was repeated until the children choose the smaller item, demonstrating they understood the instructions.
Next, the children were granted the choice between the small item now and the large item now. This task continued until the children chose the large item on four consecutive trials, showing they understood the task.
Then, to enhance their self control, the children chose between a small item now, a large item later, and a large item later coupled with a problem solving task during the delay. Whenever the children choose a larger item, the delay was increased incrementally. The primary result was that children could embrace a longer delay, indicating self control and diminution in discounting, if they undertook some activity during the delay. Thus, to reduce temporal discounting, workshops could progressively increase the delay period but ensure this interval is occupied by an engaging task.
Temporal discounting is associated with many other concepts, such as consideration of future behavior (Strathman, Gleicher, Boninger, & Edwards, 1994) and impulsive behavior. This relationship between temporal discounting and impulsive behavior is generally stronger when positive affect is elevated (Koff & Lucas, 2011).
In one study, conducted by Koff and Lucas (2011), participants completed the Barratt Impulsiveness Scale, a task to gauge temporal discounting of money, and a scale to gauge mood. One facet of impulsivity, limited planning of the future, tended to coincide with a preference towards small monetary rewards now to more sizeable monetary rewards in the future. Nevertheless, this relationship was especially pronounced when positive affect was elevated. Conceivably, when individuals experience positive emotions, their preferences towards immediate rewards are more likely to translate into actual behavior, manifesting as impulsivity. When individuals are dejected in contrast, their preferences towards immediate rewards are impeded and do not translate into actual behavior as frequently.
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