THEORETICAL REVIEW
Behavioral trainings and manipulations to reduce delay discounting:
A systematic review
Hanneke Scholten1 &Anouk Scheres1&Erik de Water1,2&Uta Graf1&Isabela Granic1&Maartje Luijten1
# The Author(s) 2019 Abstract
In everyday decision-making, individuals make trade-offs between short-term and long-term benefits or costs. Depending on many factors, individuals may choose to wait for larger delayed reward, yet in other situations they may prefer the smaller, immediate reward. In addition to within-subject variation in the short-term versus long-term reward trade-off, there are also interindividual differences in delay discounting (DD), which have been shown to be quite stable. The extent to which individuals discount the value of delayed rewards turns out to be associated with important health and disorder-related outcomes: the more discounting, the more unhealthy or problematic choices. This has led to the hypothesis that DD can be conceptualized as trans-disease process. The current systematic review presents an overview of behavioral trainings and manipulations that have been developed to reduce DD in human participants aged 12 years or older. Manipulation studies mostly contain one session and measure DD directly after the manipulation. Training studies add a multiple session training component that is not per se related to DD, in between two DD task measurements. Ninety-eight studies (151 experiments) were identified that tested behavioral trainings and manipulations to decrease DD. Overall, results indicated that DD can be decreased, showing that DD is profoundly context dependent and changeable. Most promising avenues to pursue in future research seem to be acceptance-based/mindful-ness-based trainings, and even more so manipulations involving a future orientation. Limitations and recommendations are discussed to identify the mechanistic processes that allow for changes in discount rate and behavior accordingly.
Keywords Delay discounting . Temporal discounting . Trainings . Manipulations . Health behaviors . Trans-disease process
Glossary of acronyms in text and tables
ADHD Attentional-deficit/hyperactivity disorder ATM Advisor-teller money manager
BMT Brief motivational training BS Between-subject design
C Control condition
CBT Cognitive behavioral therapy CDE Cancer death experience CLT Construal level theory
CM Contingency management
CO Carbon monoxide
DD Delay discounting
DSM Diagnostic and Statistical Manual of Mental Disorders
E Experimental condition EFT Episodic future thinking EPT Episodic past thinking FDR Fixed delayed reward
FF Future focus
FIR Fixed immediate reward FITB Fill-in-the-blank HC Healthy controls
HYP DD Hypothetical delay discounting task
I Investment
IGD Internet gaming disorder
NI No investment
NTF Nontemporal focus
PF Present focus
PR DD Potentially real delay discounting task Part of this research was presented at a Thematic Meeting on Addiction in
Marquette, Michigan, USA at 9 September 2016. * Hanneke Scholten
h.scholten@bsi.ru.nl 1
Behavioural Science Institute, Radboud University, P.O. Box 9104, 6500, HE Nijmegen, The Netherlands
2 Icahn School of Medicine at Mount Sinai, New York, NY, USA
https://doi.org/10.3758/s13423-019-01629-2
PSA Polysubstance dependent alcoholics REAL DD Real delay discounting task SDT Social delay discounting task SFAS Substance-free activity session SFT Semantic future thinking STI Sexually transmitted infection VDR Variable delayed reward VIR Variable immediate reward
WM Working memory
WS Within-subject design
Life is full of choices between options that are immediately rewarding and options that are only rewarding in the future. For example, shall I smoke a cigarette right now, or shall I refrain from smoking to stay healthier in the future? Individuals have the tendency to prefer immediate, smaller rewards over larger, but delayed rewards (Logue,1988). This phenomenon is described as delay discounting (DD)— also referred to as temporal discounting or time discounting— and is often viewed as a measure of impulsive choice (e.g., Ainslie,1975; Monterosso & Ainslie,1999; Rachlin,1989). DD refers to the decrease in the subjective value of a reward as the delay to its receipt increases (Ainslie,1992; Critchfield & Kollins,2001; L. Green & Myerson,1993; Hamilton et al., 2015; Rachlin,1989). The extent to which individuals dis-count the value of delayed rewards turns out to be associated with important health and disorder-related outcomes, and there is growing interest in trainings and manipulations that decrease heightened DD. The current systematic review pre-sents an overview of behavioral trainings and manipulations that have been developed to reduce DD.
A DD task in which participants have to choose between a series of smaller–sooner (e.g., $5 today) and larger–later rewards (e.g., $10 in 2 weeks) is commonly used to assess these preferences (L. Green & Myerson, 2004; Stanger, Budney, & Bickel,2013). The magnitude of the smaller– sooner reward and the delay preceding the larger reward are varied across choices in DD tasks, to determine an individual’s indifference point for each delay (Critchfield & Kollins, 2001). The indifference point, or subjective value, is defined as the magnitude of the smaller–sooner reward at which an individual shows no clear preference for either the smaller–sooner or later–larger reward. These indifference points/subjective values are used to define the rate at which individuals discount delayed rewards (Bickel, Jarmolowicz, Mueller, Koffarnus, & Gatchalian, 2012b; Scheres, de Water, & Mies,2013a).
The choices in DD tasks can either be hypothetical, poten-tially real, or real. In hypothetical DD tasks, participants do not receive the rewards they choose, and they do not experience the waiting times (Scheres, de Water, et al.,2013a). In poten-tially real DD tasks, participants are informed that one choice will be selected at the end of the task, and participants are paid
accordingly. This task relies on the assumption that participants will choose on each trial as if that trial is the one that will be selected. In real tasks, all chosen rewards are paid, and all delays are experienced during the test session (Scheres, de Water, et al., 2013a). Another method to assess DD, is the fill-in-the-blank (FITB) task (Chapman, 1996). In this task, participants answer only one question at each given delay, in comparison to the titrating procedures used in DD tasks (Weatherly & Derenne, 2011; Weatherly & Terrell, 2010). Specifically, for each choice participants indicate themselves what amount they are willing to accept immediately rather than having to wait for the full amount of the outcome that will be delayed for X amount of time (Weatherly & Derenne,2011).
Frequently, unhealthy or problematic behaviors have a de-layed effect on health—for example, smoking a cigarette right now has detrimental effects on one’s health in the long run. This has led researchers to believe that an individual’s tenden-cy to make unhealthy or problematic choices is related to his or her discount rate. Supporting this belief, discount rate is highly correlated with a variety of health behaviors and disor-ders, with medium effect sizes across studies (Amlung, Petker, Jackson, Balodis, & MacKillop,2016; Jackson & MacKillop, 2016; MacKillop et al., 2011). Specifically, increased DD rates are characteristic of maladaptive and unhealthy behav-iors including alcohol dependence (e.g., Bobova, Finn, Rickert, & Lucas, 2009; Mitchell, Fields, D’Esposito, & Boettiger, 2005), drug dependence (e.g., Bickel, Landes, et al.,2011a; Kirby & Petry,2004; Monterosso et al.,2007), gambling problems (e.g., Reynolds,2006), tobacco use (e.g., Audrain-McGovern et al.,2009; Baker, Johnson, & Bickel, 2003; Bickel, Yi, Kowal, & Gatchalian,2008; Fields, Leraas, Collins, & Reynolds,2009), overeating (e.g., Amlung et al., 2016; Weller, Cook, Avsar, & Cox,2008), attention-deficit/ hyperactivity disorder (ADHD; Demurie, Roeyers, Baeyens, & Sonuga-Barke,2012; Jackson & MacKillop,2016; Patros et al.,2016; Scheres, Tontsch, Thoeny, & Kaczkurkin,2010), conduct disorder (White et al.,2014), and risky sexual behav-iors (Chesson et al.,2006). For example, as a group, individ-uals who smoke consistently show higher DD rates than con-trols do (Amlung & MacKillop, 2014; MacKillop et al., 2011). Thus, DD is consistently linked with a variety of prob-lematic and unhealthy behaviors, and there is initial evidence from developmental studies that increased discounting rates contribute to the development and maintenance of these be-haviors (Audrain-McGovern et al.,2009; Ayduk et al.,2000; Breaux, Griffith, & Harvey, 2016; Campbell & Von Stauffenberg, 2009; Khurana et al., 2013; Krishnan-Sarin et al., 2007; Passetti, Clark, Mehta, Joyce, & King,2008; Sheffer et al., 2012; Stanger et al., 2012). Although more studies are needed to replicate these effects, Audrain-McGovern et al. (2009), for example, showed with a prospec-tive longitudinal cohort study spanning midadolescence to young adulthood (ages 15–21 years old) that heightened
baseline DD rates were a significant predictor of smoking initiation over time (11% increase in the odds of smoking uptake).
This body of evidence has led to the hypothesis that DD can be conceptualized as a trans-disease process that is shared across different disorders (Bickel et al.,2012b., ; Bickel, Quisenberry, Moody, & Wilson,2015). Consequently, inter-vening in such a trans-disease process could be very promis-ing for various reasons. First and foremost, if higher discount rates function as a behavioral marker of health behaviors and disorders, then manipulating discount rates might change mul-tiple health behaviors and disorders as well (Koffarnus, Jarmolowicz, Mueller, & Bickel,2013). Furthermore, it offers the opportunity to better understand and investigate comorbid-ity (i.e., the co-occurrence of two or more disorders). The presence of two or more disorders is not unexpected when both are originating from the same trans-disease process.
Interindividual differences in discounting rates are highly stable. This had led some to argue that the discounting rate should be viewed as a personality trait (Odum,2011 )—name-ly, someone’s relative DD rate is highly stable. At the same time, there is a growing number of studies that suggest that intraindividual differences in DD rate are substantial as well: Within individuals, DD rate changes as a function of contextual/situational factors (Bickel, 2015; Gray & MacKillop,2015; Odum,2011). Therefore, there is growing attention for trainings and manipulations that successfully tar-get and decrease heightened DD (e.g., Bickel, Quisenberry, Moody, & Wilson,2015; Koffarnus et al.,2013). Instead of focusing on specific disorders to identify trainings and manip-ulations that work, a more successful approach might be to develop trainings and manipulations that are effective across a variety of disorders.
While attention to the topic of reducing DD is growing, little is understood about effective ways to alter height-ened discount rates. Understanding which trainings and manipulations are worth pursuing in the future, and which of those seem less effective in reducing DD, can help us optimize the application of this body of work. Although the literature provides a small number of important narra-tive reviews discussing the promise of DD trainings and manipulations (e.g., Bickel et al., 2015; Gray & MacKillop, 2015; Koffarnus et al., 2013; Lempert & Phelps, 2016), a systematic review was not performed at the time of our search. However, recently, a systematic review and meta-analysis was published on the same topic (Rung and Madden, b). Compared with the current sys-tematic review, Rung and Madden (b) took a more meth-odological and meta-analytic approach to determine the efficacy of different methods to reduce DD, whereas we took a more theoretical approach to identify promising routes for future research. Furthermore, Rung and Madden (2018b) included a review and analysis of animal
studies, studies with child populations, and studies before 1990, but did not report on possible effects of DD train-ings or manipulations on behavior. The purpose of the current systematic review is to present an overview of behavioral trainings and manipulations available in the literature to reduce DD, and improve behavior according-ly, in human adolescent and adult participants.
Studies included in the review will be separated in two main categories. On the one hand, there are studies using manipulations: These studies manipulate the DD task (e.g., change wording in task) or add a priming procedure shortly before the DD task. Most of these studies include only one session and one moment of measuring DD rates. On the other hand, there are studies applying trainings: These studies add a training component that is not directly related to DD in between two DD task measurements. In most studies, these trainings are delivered in multiple ses-sions, but some studies include only one session of train-ing. Within these two main categories, studies will be further classified based on the content of the training or manipulation. DD is the main outcome that is evaluated in the current systematic review, although secondary behav-ioral outcomes, such as smoking or eating behaviors, will also be discussed. The central research questions in this systematic review are whether there are effective ways of decreasing DD and whether there are associated effects on behavioral outcomes. This systematic review is a first step in systematically summarizing the research regarding de-creasing DD. As this literature is rather diverse and large, we are not aiming to offer a coherent theoretical frame-work or compare effectiveness of studies by computing effect sizes. Yet we hope to identify promising routes for future research and classify overarching mechanistic processes that allow for changes in discount rate and be-havior accordingly.
Method
Inclusion criteria
Studies were included in the systematic review if (1) they included human participants; (2) the participants were 12 years or older; (3) (one of) the outcome measure represented monetary DD; (4) a training or manipulation was employed; (5) the training or manipulation was behavioral in nature (no medication or neuromodulation studies are included); (6) the study aimed to decrease DD (instead of increase); (7) DD choices were made for the self instead of for others; (8) they included a training or manipulation that had training and/or clinical potential—for example, the mere manipulation of placing an individual in a certain environment (gambling vs. nongambling), or the experimental manipulation of reward magnitude or sign (gains vs. losses) were manipulation
categories excluded from this review; (9) the sample size was >10; (10) they were published between 1990 and April 2017; and (11) were published in an English-language peer-reviewed journal. To reduce heterogeneity, we narrowed our search by including only studies using monetary outcomes that aimed to decrease DD via behavioral trainings or manipulations.
Search strategies
Literature search and selection were carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Moher, Liberati, Tetzlaff, Altman, & The PRISMA Group,2009). A three-step pro-cedure was used to identify relevant studies. First, we searched relevant databases (i.e., Pubmed, PsychInfo, and Web of Science) to identify studies that met inclusion criteria summarized above. All synonyms of the word delay discounting (i.e., delay discount*, temporal dis-count*, inter temporal choice and time discount*) and all possible variants of words like change and decrease (alter*, reduc*, manipulate*, train*, modify*, adjust*, transform*, convert*, reform*, diminish*, attenuate*, declin*, adapt*, improv*, amend*, ameliorat*, learn*, de-velop*) were entered in the databases. We included title, abstract, keywords, and topic as search areas. Second, to further identify relevant studies, the reference lists of all studies classified in step one were reviewed. Finally, we checked the reference lists of already existing reviews (i.e., Gray & MacKillop, 2015; Koffarnus et al., 2013; Lempert & Phelps,2016) for additional studies.
Search results
The literature search in Pubmed, PsychInfo, and Web of Science resulted in 8,969 hits (1,101; 6,584; and 1,284 hits, respectively). We detected 1,520 duplicates, and removing these resulted in 7,449 unique references. The reference lists of the identified studies yielded eight additional studies. No extra studies were identified when checking the reference lists of the already existing reviews. Authors H.S. and U..G inde-pendently determined whether the inclusion criteria were met by reading the titles and abstracts. We identified a total of 178 potentially relevant studies at this point. Next, all 178 full-text studies were screened using the same inclusion criteria, and this resulted in a final number of 98 studies relevant for the review. The selected studies cover a wide variety of behavioral trainings and manipulations that change DD in adolescents and adults. The whole literature search and selection process is displayed in Fig.1.
Results
Characteristics of included studies
Characteristics and results of the 98 studies included in this systematic review are summarized in Table 1 and 2. Table1 covers all studies applying a training, with a total of 19 studies (each covering one experiment; thus 19 ex-periments) published between 2008 and 2017. The major-ity (n = 14; 74%) of these studies included a clinical pop-ulation, specifically smokers, individuals with Internet gaming disorder (diagnosed based on Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [DSM5]“condition for further study” symptoms), individ-uals dependent on marijuana, opioids, alcohol, cocaine, stimulants, or individuals on polysubstance and methadone maintenance. The remaining 26% (n = 5) of studies tested their training in healthy controls. Seven out of the 19 stud-ies (37%) also reported effects of their training on actual behavior such as smoking or cocaine abstinence, in addi-tion to results on DD.
All studies using manipulations to change DD are displayed in Table 2, with a total of 79 studies published between 2001 and 2017. A total of 132 experiments were conducted within these 79 studies. Most experiments (n = 118; 89%) included healthy controls as their target population; however, 14 experiments (11) included clinical populations (sometimes in combination with a healthy control sample). These clinical populations included smokers, individuals with Internet gaming disorder, obese individuals, alcohol-dependent or substance-alcohol-dependent individuals, and ADHD or amnestic patients. Of the experiments, 5% (n = 6) reported effects of the manipulations on actual behavior, such as caloric intake, in addition to the effect on DD. For clarification pur-poses, we divided the manipulations in four main categories broadly covering the variety of manipulations in the literature and discuss them accordingly: future, social factors, emotion, and framing. Please note that this division is purely subjective, and some studies combine multiple manipulation categories.
There are far more manipulation experiments available in the literature (n = 132; 87%), compared to trainings (n = 19; 13%). Almost all experiments included adults; only two ex-periments (Fassbender et al.,2014, Study 5; Radu, Yi, Bickel, Gross, & McClure,2011, Study 2) also included participants younger than 18. Inspecting the samples more carefully, it becomes clear that more than a third of all manipulation ex-periments (n = 52; 39%) has tested its manipulation in healthy control college student samples with a higher percentage of female than male participants (>60%). In the training experi-ments, the percentage of healthy control college student sam-ples with more female than male participants was much lower (n = 4; 21%).
With regard to measuring DD as the main outcome variable, most experiments employed either a hypothetical DD task (n = 77; 51%), a potentially real DD task (n = 46; 30%) or a hypothetical FITB task (n = 22; 15%). A small number of experiments used a real DD task (n = 2; 1%), a potentially real FITB task (n = 1; 1%) or combined two methods within one experiment (n = 3; 2%). One experi-ment combined a real DD and a hypothetical DD task, one experiment combined a potentially real DD task with a hypothetical DD task, and another experiment combined a hypothetical DD task with a hypothetical FITB task.
General results
Results of the current review show that 26% (n = 5) of the experiments evaluating the effects of trainings find the expect-ed rexpect-eductions in DD, whereas 58% (n = 11) found null results or unexpected increases in DD. The remainder three studies (16%) found mixed results; these studies found the expected reductions in DD on a substance-related DD task, but not on a monetary DD task. Of the experiments that included a second-ary behavioral outcome (n = 7) all found the expected positive effects on behavior.
Table 1 Cha ra cte ri stic s and re sult s o f studies including trainings Study Exp eriment Participants T ask R esult o n DD S eco ndary outcome T ype N (mal e) A g e T ype R ewa rds D el ays Co nt in ge nc y m an ag em en t (CM; m a in co m p o n ent ) Kurti & Dallery (201 4 ) Smokers 2 0 (13) 41. 4 HYP DD VIR, FDR 1w –10y WS No int eraction effect conditi on and time C: No ex er ci se ➔ DD – E1: Exercise ➔ DD – Int eraction effect conditi on and tim e? C: No CM ➔ DD ? E2: C M ➔ DD ? Int eraction ef fect conditi on and time E: Exercise + C M ➔ sm oki ng ↓ E: No ex er cise + C M ➔ sm okin g ↓ E: Exercise + n o C M ➔ smo k ing − C: No ex er ci se + n o C M ➔ sm o k in g − La nde s et al. ( 201 2 ) Op io id-d ep en de n t pa tie nt s 15 9 (83) 33. 8 HYP DD VIR, VDR 1d –25 y B S No int eraction effect CM and time C : Bu pr en or p h in e ➔ DD ↓ E: B u p re n or ph ine + CM ➔ DD ↓ – Pe ters et al. ( 201 3 ) Ma riju an a-de pe nd en t in div idua ls 93 (8 0) 26. 1 R EAL D D V IR, FDR 7s –28 s B S Int eraction effect conditi on and time C : CBT only ➔ DD ↑ E1: C M abst in e n ce on ly ➔ DD − E2: C B T + C Mad h er e n c e ➔ DD − E3: C M abst in e n ce + CBT ➔ DD − – We id b er g et al. ( 201 5 ) T rea tm en t-se ek ing sm oke rs 11 6 (44) 45. 48 HYP DD VIR, FDR 1d –25 y B S No int eraction effect conditi on and time C : CBT only ➔ DD − E: C M + C BT ➔ DD − Int eraction effect conditi on, tim e, an d se x In wo me n: C : CBT only ➔ DD − E: C M + C BT ➔ DD ↓ In m en : C : CBT only ➔ DD − E: C M + C BT ➔ DD – End o f treatment: Int eraction ef fect conditi on and time C: C B T o nly ➔ smoking abs tinence – E: CM + C BT ➔ smoking abs tinence ↑ Follow-up: No int eraction ef fect conditi on and time C: CB T o nly ➔ smo k ing ab stin en ce − E: CM + C BT ➔ smoking abs tinence − Yi et al . ( 200 8 ) Smok er s 5 6 (3 6 ) 25. 9 1 . HYP DD (m o ne y ) 1. HYP DD (c ig ar et tes ) VIR, FDR 1w –25y BS Int eraction effect conditi on and time M o ne y: C: S m o k e as n or mal ➔ DD − E: C M ➔ DD ↓ Cig ar et tes : C: S m o k e as n or mal ➔ DD − E: C M ➔ DD ↓ Int eraction ef fect conditi on and time E: C M ➔ CO le ve ls ↓ No co n tr o l condition Yo o n et al . ( 200 9 ) Smok er s 2 8 (1 9 ) 28. 6 1 . HYP DD (only mon ey ) VIR, FDR 1d –25 y B S M o ne y: Int eraction ef fect conditi on and time C: Control condition ➔ CO levels –
Ta b le 1 (continued) Study Exp eriment Participants T ask R esult o n DD S eco ndary outcome T ype N (mal e) A g e T ype R ewa rds D el ays 2. HYP DD (m o ne y an d cig ar ettes) No int eraction effect conditi on and time C: Control condition ➔ DD − E: C M ➔ DD − M o ne y an d ci ga re tte s: Int eraction effect conditi on and time C: Control condition ➔ DD − E: C M ➔ DD ↓ E: C M ➔ CO le ve ls ↓ Mo ne y-ma na g em ent -b as ed tr ain in g Bla ck & Rosen (201 1 ) Coca ine and/or alco h o l u ser s 90 (4 5) Adul ts PR DD VIR, VDR 7d –18 6d BS Int eraction effect conditi on and time C: Control condition ➔ DD ↑ E: Mon ey man ag em ent -b ase d tra ini ng ➔ DD − Int eraction ef fect conditi on and time C: Control condition ➔ co ca ine ab stin enc e ↓ E: Mon ey man ag em en t-b ase d tra ini ng ➔ co ca ine ab stin en ce − DeHart et al. ( 201 6 ) HC 31 7 (120 ) 22. 21 HYP DD VIR, FDR 1w-2 5 y BS Int eraction effect conditi on and time C: Ab nor ma l ps yc holo gy condit ion ➔ DD – E: Fi nan ci al edu ca tion condit ion ➔ DD ↓ – Br ief m o tiva tio na l tr a in in g in co m b in a ti on with su bs ta nc e-fr ee ac tiv ity ses sio n De nnh ar dt et al. ( 201 5 ) Heavy d rinking college students 97 (4 0) 20. 10 HYP DD –– BS No int eraction effect conditi on and time C: Brief m otiva tional training (BMT) + ed uca tio n se ssi on ➔ DD − E: B MT + S u b stan ce-fr ee ac tiv ity ses sio n (SF AS) ➔ DD − – Mu rp hy et al. ( 201 2 ) Heavy d rinking college students 82 (4 1) 18. 5 HYP DD VIR, VDR 7d –18 6d BS No int eraction effect conditi on and time C: BMT + relaxati on tra ini ng ➔ DD − E: B M T + SF AS ➔ DD − Int eraction ef fect conditi on and time C: BMT + relaxati on tr aining ➔ al co ho l p ro ble m s − E: B M T + SF AS ➔ alc o h o l pro b le ms ↓ Co gn it ive b eh a v io ra l th era py (CBT ; m ain com pone nt) De W ilde et al. ( 201 3 ) po lys ubs tan ce de pe nd en t al coh oli cs (P SA) 37 (2 9) 31. 61 HYP DD VIR, VDR 2d –72 0d WS No int eraction effect conditi on and time E: C B T ➔ DD – No co n tr o l condition – Secades -V illa et al. ( 201 4 ) T rea tm en t-se ek ing sm oke rs 80 (2 7) 38. 90 HYP DD VIR, FDR 1d –25 y W S No int eraction effect conditi on and time E: C B T ➔ DD − –
Ta b le 1 (continued) Study Exp eriment Participants T ask R esult o n DD S eco ndary outcome T ype N (mal e) A g e T ype R ewa rds D el ays No co n tr o l condition End o f treatment: No int eraction effect sm oking status and time E: Sm oke r➔ DD − E: Abst ainer ➔ DD − 12 m onth fo llow-up: Int er ac tio n effe ct sm oking status and time E: Sm oke r➔ DD − E: Abst ainer ➔ DD ↓ Ac ce pt an ce -B a sed /Min df ulness-Based T rainings He ndr ic kson & Ra sm u sse n ( 201 3 ) Stud y2 HC 10 2 (29) 25. 46 1. HYP DD (m o ne y ) 2. HYP DD (foo d) VIR, VDR Mo ne y: 1d –36 5d Food : 1h –-20h BS Mo ne y: No int eraction effect conditi on and time C: Control condition ➔ DD − E: Min d fu lness-based eati n g tra ini ng ➔ DD − Fo od: Int eraction effect conditi on and time C: Control condition ➔ DD – E: Min d fu lness-based eati n g tra ini ng ➔ DD ↓ – He ndr ic kson & Ra sm u sse n ( 201 7 ) HC 34 8 (134 ) 18. 29 1. HYP DD (m o ne y ) 2. HYP DD (foo d) VIR, VDR Mo ne y: 7d –18 6d Food : 0. 5h –24h BS Mo ne y: No int eraction effect conditi on and time C1: C ontrol conditi on ➔ DD − C2: N utritional DVD ➔ DD − E: Min d fu lness-based eati n g tra ini ng ➔ DD − Fo od: Int eraction effect conditi on and time C1: C ontrol conditi on ➔ DD − C2: N utritional DVD ➔ DD − E: Min d fu lness-based eati n g tra ini ng ➔ DD ↓ – Mo rr iso n et al. ( 201 4 ) HC 30 (1 5) 21. 5 (18– 41 ) HYP DD VIR, FDR 1w –25y BS Int eraction effect conditi on and time C: W ai tlis t➔ DD − E: Acc ep ta nce -bas ed tra ini ng ➔ DD ↓ – Ya o et al . ( 201 7 ) Indi vidu al s w ith In ter n et ga min g 25 (? ) / 2 1 (? ) 22. 28 / 22. 00 HYP DD VIR, VDR 7d –18 6d WS Main ef fec t gr ou p In te ra ction ef fec t g ro u p an d tim e In h ea lth y contr o l g ro up:
Ta b le 1 (continued) Study Exp eriment Participants T ask R esult o n DD S eco ndary outcome T ype N (mal e) A g e T ype R ewa rds D el ays di sor de r (IGD) / H C Healthy control group ➔ DD − IGD g ro u p ➔ DD ↑ Int er ac tio n effe ct g ro u p and ti me In he althy con tro l gr ou p : C: No tra in ing ➔ DD − In IGD g ro u p : E: Gr ou p b eh av io ral tra in in g combining reali ty therapy and mind fu lne ss m edi tat ion ➔ DD ↓ C: No tra in ing ➔ In ter ne t ad dic tion sym ptom s ↑ In IGD g ro u p : E : G rou p b eh av io ra l tra in in g combining rea li ty therapy an d min df ulne ss meditation ➔ Int er n et ad dic tio n sy m pto m s ↓ W o rking m emo ry tra ining B ick el et al . ( 201 1b ) Stim ula n t-de pe nde nt in div idua ls in su bst anc e-a bus e treatment 27 (2 0) 38. 6 1 . HYP DD 2. PR DD VIR, FDR HYP DD: 1d –25 y PR DD: 1d –6m BS Int eraction effect conditi on and time C: Control condition ➔ DD − E: W o rking m emory training ➔ DD ↓ – Ra ss et al. ( 201 5 ) M eth ad one maintenance patie nt s 56 (2 6) 43. 4 1 . HYP DD 2. REAL DD VIR, FDR HYP DD: 1d –25 y REAL DD: 5s –80 s BS Hypothetical DD: No main or interaction ef fect s C: Control condition ➔ DD − E: W o rking m emory training ➔ DD − Real DD: Ma in ef fe ct ti me (r ea l rewa rd s) C: Control condition ➔ DD ↓ E: W o rking m emory training ➔ DD ↓ – V isualization T rai n ing Pa rthasarathi et al. ( 201 7 ) HC 48 (1 5) 24. 6 P R D D V IR, VDR 1d –18 0d BS No int eraction effect conditi on and time C: Control condition ➔ DD − E: V isualizat ion training ➔ DD − M ain ef fe ct co nd itio n at p o st-test C: Control condition ➔ DD − E: V isualizat ion training ➔ DD ↑ – Not e. HYP D D = hypothetical delay discounting task; PR DD = potentially real delay dis counting tas k; REAL DD = real d elay di scountin g task; FI TB = fill-in-th e-blank task VI R = va ria b le immedia te rewa rd; F IR = fi xe d immedi ate re w ar d ; VDR = v ar iabl e d ela y ed re wa rd; FD R = fixed de laye d rew ar d WS = w ithin-subject design; BS = between-s ub ject design; E = experiment al condition; C = control condition; HC = healthy con trols ↓ = d elay dis counting d ecreased; ↑ = delay discounting increased; – = n o changes in d elay discounting
Table 2 Cha ra cte ri stic s and re sult s o f studies including manipulations Study Experiment Participants T as k Result on DD S econd ary outcome T ype N (m al e) Age T ype R ewa rds D el ay s Futur e Episo d ic futur e thinking (EFT) Beno it et al. ( 201 1 ) H C 12 (4 ) 27.3 (2 0.6 –36.3) HYP DD FIR, VDR 30 –360d WS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ Interacti o n ef fect con d ition and emotional intensity Low emo tional intensity: C: Control condition ➔ DD – E: EFT condition ➔ DD – High emotional intensity: C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ – Bulley and Gullo ( 2017 ) H C 48 (1 5 ) 20.67 HYP DD VIR, FDR 2 d– 365d WS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ – Chen g et al. ( 2012 ) Exp. 1 H C 6 4 (3 4 ) 21.1 HYP DD VIR, VDR 1w BS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ – Chio u & W u ( 2016 ) S m okers 90 (6 9 ) 31.4 HYP DD FIR, VDR 1y BS Main ef fect co n d ition C1: C ontrol cond it io n ➔ DD – C2: S emantic futu re thinkin g (SFT) conditio n ➔ DD – E: EFT condition ➔ DD ↓ Main ef fect con d ition o n smoking du ri n g survey/smok ing next week C1: Control conditio n ➔ smoking du ri n g survey/smok ing next week – C2: SFT cond ition ➔ smoking du ri n g survey /smoking nex t week – E: EFT co n dition ➔ smoking du ri n g survey/smok ing next week ↓ Mediation ef fect condition and D D o n smo k ing during survey/smok ing next week E: EFT ➔ DD ↓ ➔ smoking du ri n g survey/smok ing next week ↓ Daniel et al. ( 2013 b ) O b ese in d ividuals 26 (0 ) 26.43 HYP DD VIR, FDR 1 d – 2y BS Main ef fect co n d ition Main ef fect con d ition on caloric intake
Ta b le 2 (continued) Study Experiment Participants T as k Result on DD S econd ary outcome T ype N (m al e) Age T ype R ewa rds D el ay s C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ C: C o ntrol condition ➔ caloric intake – E: EFT co n dition ➔ caloric intake ↓ Daniel et al. ( 2013 a ) O b ese in d ividuals 48 (0 ) 1 8 – 4 0 HYP DD VIR, FDR 1 d – 2y WS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ No interacti o n ef fect con d ition and g roup Lean in d ividual g roup : C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ Obese individu al grou p : C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ -Daniel et al. ( 201 6 ) H C 81 (3 1 ) 26.07 HYP DD VIR, FDR 1 d– 6m BS Main ef fect co n d ition C1: C ontrol cond it io n ➔ DD – C2: E pisodic p ast thinkin g (EPT) cond ition ➔ DD – E: EFT condition ➔ DD ↓ – Dassen et al. ( 201 6 ) H C 95 (0 ) 20.45 HYP DD VIR, VDR 7d –186d BS Main ef fect co n d ition C1: Food-related control conditio n ➔ DD – C2: General con trol conditio n ➔ DD – E1: F o od-related E F T conditio n ➔ DD ↓ E2: G eneral EFT conditio n ➔ DD ↓ Intera ctio n ef fect condition and task content o n caloric intake Food-related task: C1: Food-related control condition ➔ caloric intake – E1: F o o d-related EFT condition ➔ caloric intake ↓ General task : C2: General con tr o l condition ➔ caloric intake – E2: Gen er al EFT condition ➔ caloric intake – Hu et al. ( 2017 ) H C 22 (8 ) 2 4 (1 9 -28) HYP DD FIR, VDR 1w –1y WS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ – Kwan et al. ( 2015 ) Am ne st ic p atients / HC 6 (6) / 2 0 (1 2 ) 55.17 / 69.2 5 HYP DD VIR, VDR 1w –10y WS Main ef fect co n d ition C: Control condition ➔ DD – E: EFT condition ➔ DD ↓ –
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s Lin & Epstein (2014 ) HC 87 (4 5 ) 40.78 HYP D D VIR, VDR 10d –70d BS Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ – L. Liu et al. ( 2013 ) Exp. 1 H C 3 2 (1 5 ) 20.62 (18 –25) PR DD VIR, VDR 1w –1m W S Main ef fect con d ition C: C o ntrol condition ➔ DD – E : P o si ti ve E F T condition ➔ DD ↓ – Exp. 2 H C 3 1 (1 6 ) 20.74 (18 –25) PR DD VIR, VDR 1w –1m W S Main ef fect con d ition C: C o ntrol condition ➔ DD – E: Negativ e EFT condition ➔ DD ↑ – Exp. 3 H C 3 0 (1 4 ) 21.48 (18 –25) PR DD VIR, VDR 1w –1m W S No m ain ef fect cond it io n C: C o ntrol condition ➔ DD – E: Neutral EFT condition ➔ DD – – Palombo et al. ( 20 1 5 ) Amn estic pa ti ent s / H C 9 (6) / 1 3 (6) 61.22 (45 –85) /6 5 HYP D D FIR, VDR 2m –2y W S Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ Intera ctio n ef fect con d ition and g roup In he al thy con tr o l gr ou p : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ In amnestic patient group : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD – – Palombo et al. ( 20 1 6 ) Exp. 1 A mn estic pa ti ent s / H C 9 (6) / 1 2 (7) 58.78 (47-73 ) / 60. 2 HYP D D FIR, VDR 2m –2y W S No m ain ef fect cond it io n C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD – Intera ctio n ef fect con d ition and g roup In he al thy con tr o l gr ou p : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ In amnestic patient group : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↑ – Exp. 2 A mn estic pa ti ent s / H C 8 (5) / 1 2 (6) 60.63 / 58.8 HYP D D FIR, VDR 2m –2y W S Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ No inter actio n ef fect condition and g roup –
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s In he al thy con tr o l gr ou p : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ In amnestic patient group : C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ Peters & Büchel ( 2010 ) Exp. 2 H C 3 0 (1 5 ) 25.4 PR D D FIR, VDR 1d –233d WS Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ – Sasse et al. ( 20 1 5 ) HC 23 (1 2 ) 24.96 (21 –30) PR DD FIR, VDR 1d –190d WS Main ef fect con d ition C1: Control conditio n ➔ DD – E1: F amiliar EFT condition ➔ DD ↓ E2: Un fa m iliar EFT condition ➔ DD ↓ – Sasse et al. ( 20 1 7 ) HC 22 (9 ) 66.55 PR DD FIR, VDR 1d –190d WS No m ain ef fect cond it io n C1: Control conditio n ➔ DD – E1: F amiliar EFT condition ➔ DD – E2: Un fa m iliar EFT condition ➔ DD – – Snider et al. ( 20 1 6 ) Alco h o l-depend ent in d ividuals 50 (3 8 ) 41.15 HYP D D VIR, FDR 1d –1y BS Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ Main ef fect con d ition o n hypoth etic al alcoho l purchase C: C o ntrol condition ➔ hypoth etic al alcoho l purchase – E: EFT co n dition ➔ hypoth etic al alcoho l purchase ↓ Stein et al. ( 20 1 6 ) S m ok er s 4 2 (24 ) 3 9 .2 6 H Y P DD V IR , F D R 1 d– 1y BS Main ef fect con d ition C: C o ntrol condition ➔ DD – E: EFT co n dition ➔ DD ↓ Main ef fect con d ition o n cigaret te self -admin is tr atio n C: C o ntrol condition ➔ cigaret te self -admin is tr atio n – E: EFT co n dition ➔ cigaret te self -admin is tr atio n ↓ W u et al. ( 2017 ) Exp. 1 H C 9 0 (4 8 ) 20.9 PR D D FIR, VDR 1y BS Main ef fect con d ition C1: Control conditio n ➔ DD – C2: SFT cond ition ➔ DD – E: EFT co n dition ➔ DD ↓ – Exp. 2 H C 9 0 (4 5 ) 20.2 PR D D FIR, VDR 1y BS Main ef fect con d ition C1: Control episod ic thinking (ET) ➔ DD – –
Ta b le 2 (continued) Study Experiment Participants T as k Result on DD S econd ary outcome T ype N (m al e) Age T ype R ewa rds D el ay s C2: ET p resen t-self ➔ DD – E: EFT condition ➔ DD ↓ C o n n ec ti v it y to fut u re (Se lf ) Bartels & Urminsky (201 1 ) Exp. 1 H C 141 (– ) Gra d u ating seniors PR DD FIR, VDR 1w –1y BS Main ef fect co n d ition C: L o w co n nectedness ➔ DD – E: Hig h co n n ectedness ➔ DD ↓ – Exp. 2 H C 118 (– )1 8– 29 PR DD VIR, FDR 1 w –1y BS Main ef fect co n d ition C: L o w co n nectedness ➔ DD – E: Hig h co n n ectedness ➔ DD ↓ – Exp. 3 H C 9 7 (– ) U ndergraduates HYP FITB – Now –1y BS Main ef fect co n d ition C: L o w co n nectedness ➔ DD – E: Hig h co n n ectedness ➔ DD ↓ – Exp. 4 H C 7 1 (– ) Adults HYP FI TB – 1m/1y B S Main ef fect co n d ition C: L o w co n nectedness ➔ DD – E: Hig h co n n ectedness ➔ DD ↓ – Hershfield et al. ( 201 1 ) Exp. 2 H C 2 1 (6 ) 20.08 PR DD VIR, VDR 10d –75d BS No main ef fect cond ition C: E x p o sure to other ➔ DD – E: Exp o sure to futu re self ➔ DD – – Israel et al. ( 2014 ) H C 436 (235) 25.27 HYP FITB – 1w –1y BS Pic tu re pr im ing : Main ef fect co n d ition C: Basic p rime ➔ DD ↓ E1: V acation p rime ➔ DD – E2: O lder peo p le prime ➔ DD ↓↓ T ex t priming : No main ef fect cond ition C: Basic p rime ➔ DD – E1: O lder peo p le prime ➔ DD – E2: V acation p rime ➔ DD – – Josh i & Fast ( 2013 ) Exp. 1 H C 7 3 (3 0 ) 33.1 1 (18 –63) HYP DD FIR, VDR 1y BS Main ef fect co n d ition C: L o w p o wer ➔ DD – E : H igh po w er ➔ DD ↓ – Exp. 2 H C 5 9 (2 7 ) 19.95 (18 –25) PR DD FIR, VDR 1y BS Main ef fect co n d ition C: L o w p o wer ➔ DD – E : H igh po w er ➔ DD ↓ – Kuo et al. ( 2016 ) H C 76 (2 8 ) 21.2 P R D D F IR, VDR 1y BS Main ef fect co n d ition C: Pr es en t self conditio n ➔ DD – Main ef fect con d ition on ice cream in ta ke
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E: Futu re ideal self condition ➔ DD ↓ C: Present self condition ➔ ice cr eam intake – E: Futu re ideal self condition ➔ ice cr eam intake ↓ Mediation ef fect condition and DD on ice cream in tak e E: Futu re ideal self condition ➔ DD ↓ ➔ ice cream in tak e ↓ Main ef fect con d ition on amo u nt of su g ar in reward drink C: Present self condition ➔ amo u nt of su g ar – E: Futu re ideal self condition ➔ amoun t of su g ar ↓ Pronin et al. ( 2008 ) Exp. 4 H C 140 (– ) College students PR DD FIR, FDR 2 .5 m –5m BS Main ef fect con d ition C: C h oosin g for self ➔ DD – E1: C h oosing for self in future ➔ DD ↓ E2: C h oosing for another person ➔ DD ↓ E3: C h oosing for self with re d u ced salience o f emotions ➔ DD ↓ – S h effe r et al. ( 20 1 6 ) HC 1,122 (583 ) 34.0 HYP D D VIR, VDR 7d –186d BS Main ef fect con d ition C1: N ontemporal focus condition ➔ DD – C2: Present focu s condition ➔ DD – E: Futu re focus condition ➔ DD ↓ – Construal L evel Manipulation Kelley & Schmeichel (2015 ) HC 1 1 8 (2 8 ) 21.19 (18 –43) HYP D D FIR, VDR 3m BS ABSTRACT IO N Main ef fect con d ition C: C o ntrol condition ➔ DD – E: Mortality salience condition ➔ DD ↓ – Kim et al. ( 2012 ) Exp. 4 H C 200 (90) 33.9 HYP F ITB – 3m BS Main ef fect con d ition C: Lar g e d istance condition ➔ DD – –
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E : S h or t d is ta nc e condition ➔ DD ↓ Exp. 5 H C 187 (86) 19.79 HYP F ITB – 1m BS Main ef fect con d ition C: Lar g e d istance condition ➔ DD – E : S h or t d is ta nc e condition ➔ DD ↓ – Kim et al. ( 2013 ) Exp. 1a HC 70 (3 3 ) 25.47 HYP D D VIR, FDR 1 y BS CONCRETIZ A TION Main ef fect con d ition C: Hig h -level construal ➔ DD – E: Low-level construal ➔ DD ↓ − Exp. 1b HC 81 (3 9 ) 23.60 HYP D D VIR, FDR 1 y BS CONCRETIZ A TION Main ef fect con d ition C: Hig h -level co n strual ➔ DD – E: Low-level construal ➔ DD ↓ − Exp. 2 H C 102 (35) 36.25 HYP D D VIR, FDR 1 y BS CONCRETIZ A TION Main ef fect con d ition C: Hig h -level co n strual ➔ DD – E: Low-level construal ➔ DD ↓ − Li et al. ( 2016 ) Internet ad d icts / HC 55 (39) / 5 5 (25) 19 / 1 9 HYP D D VIR, FDR 6 m BS ABSTRACT IO N Main ef fect con d ition C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ No inter actio n ef fect con d ition and g roup In he al thy con tr o l gr ou p : C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ In internet addicts g roup : C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ − Malkoc et al. ( 2010 ) Exp. 1a HC 102 (–) College students HYP F ITB – 3d-10 d BS ABSTRACT IO N Main ef fect con d ition C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ − Exp. 1b HC 522 (− ) College students HYP F ITB − 3d − 10d BS ABSTRACT IO N Main ef fect con d ition C1: Control conditio n ➔ DD – C2: Low-level co n strual ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ − Exp. 2 H C 117 (− ) College students HYP F ITB − 4w − 10w BS ABSTRACT IO N Main ef fect con d ition −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ Exp. 3 H C 231 (− ) College students HYP F ITB − 3m − 1y BS ABSTRACT IO N Main ef fect con d ition C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ − Exp. 4 H C 171 (− ) College students HYP F ITB − 3m − 1y BS ABSTRACT IO N Main ef fect con d ition C: Lo w -l ev el con st ru al ➔ DD – E : H ig h-le ve l co ns tr ua l➔ DD ↓ − Social Factors Social Context Bickel, Jarmolowicz, Mueller , Fra n ck , et al. ( 2012 a ) Smo k ers and ha za rdo u s-to -ha rm fu l dr ink er s 796 (358) 31.31 HYP D D VIR, VDR 10d –75d WS Main ef fect con d ition C: Me now , m e lat er ➔ DD – E1: M e now , w e later ➔ DD ↓ E 2 :W en o w ,w e la te r➔ DD ↓ − Charlton et al. ( 2013 ) Exp. 1 H C 3 2 (– ) College students HYP D D VIR, VDR 7d –186d WS Main ef fect con d ition C: C h oosin g for self ➔ DD – E: Ch o o sing for g rou p ➔ DD ↓ − Exp. 2 H C 3 2 (– ) College students HYP D D VIR, VDR 7d –186d WS Main ef fect con d ition C: C h oosin g for self ➔ DD – E: Ch o o sing for g rou p ➔ DD ↓ − Exp. 3 H C 108 (– ) College students HYP D D VIR, VDR 7d − 186d WS Main ef fect con d ition C: C h oosin g for self ➔ DD – E: Ch o o sing for g rou p ➔ DD ↓ − Y i et al. ( 2010 ) HC 57 (2 6 ) 33.09 HYP D D VIR, FDR 1 d− 25y / 1w − 5y WS No m ain ef fect cond it io n C: C h oosin g for self ➔ DD – E: Ch o o sing for g rou p ➔ DD – Intera ctio n ef fect con d ition and sex In males: C: C h oosin g for self ➔ DD – E: Ch o o sing for g rou p ➔ DD ↓ In females: C: C h oosin g for self ➔ DD ↓ E: Ch o o sing for g rou p ➔ DD – − Social influence Senecal et al. ( 2012 ) Exp. 2 H C 8 0 (2 7 ) 22.2 PR D D V IR, VDR 1d − 180d BS design/WS analyses Main ef fect con d ition C: Interest rate instruction ➔ DD – E: Finan cial guid e ➔ DD ↓ No dir ect co mparison between 2 conditions −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s Intera ctio n ef fect con d ition and time C: Interest rate instruction ➔ DD – E: Finan cial guid e ➔ DD ↓ No dir ect co mparison between 2 conditions Exp. 3 H C 2 0 (5 ) 26 PR DD VIR, VDR 1d –180d WS Main ef fect con d ition E: Finan cial guid e ➔ DD ↓ No co n tr o l condition Intera ctio n ef fect con d ition and time E: Finan cial guid e ➔ DD ↓ No co n tr o l condition – Exp. 4 H C 6 4 (2 4 ) 2 1 PR D D V IR, VDR 1d –180d BS design/WS analyses Main ef fect con d ition C: Impatien t peer -generated advice ➔ DD – E: Patient peer -g en erat ed advice ➔ DD ↓ No dir ect co mparison between 2 conditions – Emotion Augu stine & Larsen ( 20 11 ) Exp. 1 H C 7 0 (2 1 ) 19.66 HYP D D VIR, VDR 7– 18 6 d B S No m ain ef fect cond it io n C: Neg ative co n dition ➔ DD – E: Pos iti v e con d ition ➔ DD – Intera ctio n ef fect con d ition and neuroticism Low n eu roticism: C: Neg ative co n dition ➔ DD – E: Pos iti v e con d ition ➔ DD – High neuroticism: C: Neg ative co n dition ➔ DD ↓ E: Pos iti v e con d ition ➔ DD – – Exp. 2 H C 6 7 (1 8 ) 19.34 HYP D D VIR, VDR 7– 18 6 d B S No m ain ef fect cond it io n C: Neg ative co n dition ➔ DD – E: Pos iti v e con d ition ➔ DD – Intera ctio n ef fect con d ition and neuroticism Low n eu roticism: C: Neg ative co n dition ➔ DD ↓ E: Pos iti v e con d ition ➔ DD – High neuroticism: C: Neg ative co n dition ➔ DD – E: Pos iti v e con d ition ➔ DD – – Berndsen & v an d er Pl igt ( 2001 ) Exp. 1 H C 8 3 (− ) College students HYP F ITB – 1y –4y BS Main ef fect con d ition C: Hig h o p timism ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E: Low optimism ➔ DD ↓ Exp. 2 H C 8 1 (− ) College students HYP F ITB – 1y –4y BS Main ef fect con d ition C: Hig h o p timism ➔ DD – E: Low optimism ➔ DD ↓ − Berry et al. ( 2014 ) HC 185 (78) 20.88 HYP D D VIR, FDR 1 d– 25y BS Main ef fect con d ition C1: B uilt environments ➔ DD – C2: Geometric shap es ➔ DD – E: Natural environmen t➔ DD ↓ − Berry et al. ( 2015 ) HC 43 (1 7 ) 22.53 HYP D D VIR, FDR 1 d− 25y BS Main ef fect con d ition C: B u ilt en v ironment ➔ DD – E: Natural environmen t➔ DD ↓ − Callan et al. ( 2014 ) Exp. 1 H C 381 (164) 30.82 HYP D D VIR, FDR L ab sample + 1 st online sample: 1d–730d 2 nd online sample: 7d–365d BS Intera ctio n co n dition and victim dero g ation Unjust (f aith in justice threatened): C: Lo w v ictim derogation ➔ DD – E: High victim derogation ➔ DD ↓ Just (f aith in justice): C: Lo w v ictim derogation ➔ DD – E: High victim derogation ➔ DD – − Exp. 2 H C 238 (133) 31.10 HYP D D VIR, FDR 7 d– 365d BS Main ef fect con d ition C : N o d rug de al er condition ➔ DD – E: Drug dealer condition ➔ DD ↓ – DeSteno et al. ( 2014 ) HC 75 (3 2 ) 19 (1 8– 23) PR DD VIR, VDR 1w –6m B S Main ef fect con d ition C1: Neutral con d ition ➔ DD – C2: H appiness cond ition ➔ DD – E: Gratitude cond it io n ➔ DD ↓ – Dickens & DeSteno (2016 ) HC 105 (26) 19.31 PR DD VIR, VDR 1w –6m W S Main ef fect con d ition E: Daily gratitude ➔ DD ↓ No co n tr o l condition − Guan et al. ( 2015 ) HC 27 (7 ) 19.3 HYP D D VIR, VDR 1m WS Main ef fect con d ition C: Neg ative co n dition ➔ DD – E1: N eu tr al cond it io n ➔ DD ↓ E2: Po sitive co n dition ➔ DD ↓↓ − Hirsh et al. ( 2010 ) HC 137 (38) 20.1 (18 –2 5 ) HYP D D VIR, VDR 1w –1y B S No m ain ef fect cond it io n C1: Control conditio n ➔ DD – C2: Positive af fect induction ➔ DD – E: Negativ e af fect induction ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s Intera ctio n ef fect con d ition and extraversion L o w ext ra ve rsi o n : C1: Control conditio n ➔ DD – C2: Positive af fect induction ➔ DD – E: Negativ e af fect induction ➔ DD – Medium and h igh extraversion: C1: Control conditio n ➔ DD ↓ C2: Positive af fect induction ➔ DD – E: Negativ e af fect induction ➔ DD ↓ Huang et al. ( 2016 ) Exp. 1 H C 8 0 (4 1 ) 20.77 PR DD FIR, FDR 1 m BS Main ef fect con d ition C: C o ntrol condition ➔ DD – E: Nos ta lg ia con d ition ➔ DD ↓ − Exp. 6 H C 186 (99) 38.53 PR DD FIR, FDR 30d BS Intera ctio n ef fect con d ition and re p eatability C1: R epeatable control condition ➔ DD – C2: Unrepeatable co n trol condition ➔ DD – E1: R ep eatable n o stalgia condition ➔ DD – E2: Un re p eatable n o stalgia condition ➔ DD ↓ − Ifcher & Z ar g ha m ee ( 201 1 ) HC 69 (3 6 ) Under g ra d u ate students PR FI TB – 1d-56 d BS Main ef fect con d ition C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD ↓ − W. L iu & Aaker ( 20 0 7 ) Exp. 4 H C 8 0 (3 8 ) 20.91 HYP F ITB – Spend it/ Short-term saving / Long -t erm saving BS Intera ctio n ef fect con d ition and simulation No can cer death experience (C D E) : C: No mental simulation o f CDE ➔ DD – E: Mental simulation o f CDE ➔ DD ↓ CDE: C: No mental simulation o f CDE ➔ DD ↓ E: Mental simulation o f CDE ➔ DD ↓ − Luo et al. ( 2014 ) H C 2 2 (1 3 ) 33.6 PR D D V IR, VDR 1d –56d WS Main ef fect con d ition C: Neu tral cond ition ➔ DD – E1: Hap p y prime ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E2: F earful p rime ➔ DD ↓ Pyon e & Isen ( 201 1 ) Exp. 3 H C 9 5 (4 2 ) College students HYP D D FIR, VDR 4w –6w B S Intera ctio n ef fect con d ition and rew ar d amoun t $ 5 re wa rd: C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD – $15 or mo re reward: C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD ↓ − Exp. 4 H C 117 (– ) College students HYP D D FIR, FDR A fe w weeks B S Intera ctio n ef fect con d ition and rew ar d amoun t $ 5 re wa rd: C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD – $15 reward: C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD ↓ − Exp. 5 H C 4 4 (– ) College students HYP F ITB – 1m BS Main ef fect con d ition C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD ↓ − Exp. 6 H C 5 0 (– ) College students HYP F ITB – 3d –10d BS Main ef fect con d ition C: Neu tral cond ition ➔ DD – E: Pos iti v e con d ition ➔ DD ↓ − Q u is en be rr y et al. ( 2015 ) HC 408 (228) 30 (2 5– 37) 1. HYP D D 2. Sexual DD DT(S ) 1. VIR, FDR 2. W ithout cond o m , with condo m 1. 1d –5y 2. 1h –3m BS 1. No ef fects 2. Intera ctio n ef fect con d ition and scenario Least attractive scenario: C: P o sitive co n dition ➔ DD – E 1 :N eg at iv en o re g re t condition ➔ DD ↓ E 2 :N eg at iv er eg re t condition ➔ DD ↓ Most attr active scenario: C: P o sitive co n dition ➔ DD – E 1 :N eg at iv en o re g re t condition ➔ DD – E 2 :N eg at iv er eg re t condition ➔ DD ↓ Least sexu ally transmitted infection (S T I) partner scenario: C: P o sitive co n dition ➔ DD – E 1 :N eg at iv en o re g re t condition ➔ DD – E 2 :N eg at iv er eg re t condition ➔ DD ↓ −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s Most STI p artner scenario: C: P o sitive co n dition ➔ DD – E 1 :N eg at iv en o re g re t condition ➔ DD ↓ E 2 :N eg at iv er eg re t condition ➔ DD ↓ Raeva et al. ( 20 1 0 ) HC 57 (3 0 ) 23.07 PR DD VIR, VDR 1d –2m WS Main ef fect con d ition C: P artial feedback ➔ DD – E1: R eg ret feedback ➔ DD – E2: R ej oicing feed b ack ➔ DD ↓ − van d er W al et al. ( 2013 ) Exp. 1 H C 4 7 (2 2 ) 20.23 PR DD FIR, VDR 90d BS Main ef fect con d ition C: Urb an env ironment ➔ DD – E: Nature environmen t➔ DD ↓ − Exp. 2 H C 6 7 (1 9 ) 20.03 PR DD VIR, VDR 7d –91d BS Main ef fect con d ition C1: Control conditio n ➔ DD – C2: Urban en v ironment ➔ DD – E: Nature environmen t➔ DD ↓ − Exp. 3 H C 4 3 (1 7 ) 31.84 PR DD VIR, VDR 7d –236d BS Main ef fect con d ition C: Urb an env ironment ➔ DD – E: Nature environmen t➔ DD ↓ −
Framing Bundling Bia
łaszek and Ostaszewski (2012 ) HC 54 (2 3 ) 21.31 (18 –32) HYP D D VIR, VDR 1m –10 y W S Small rewards: No m ain ef fect cond it io n C : Si ng le sm al l re w ar d ➔ DD – E: Sequ en ce o f small re wa rds ➔ DD – Lar g e rewards: Main ef fect con d ition C : Si ng le lar g e reward ➔ DD ↓ E : S eq ue n ce of la rge re wa rds ➔ DD – − Hofmeyr et al. ( 20 1 1 ) Smo k ers + n o nsmokers 30 (1 6 ) + 30 (1 6 ) 20.97 + 2 1 .23 REAL DD VIR, FDR 1 d– 10d BS Smokers: Main ef fect con d ition C: F ree conditio n ➔ DD – E1: Su g gested conditio n ➔ DD – E2: Fo rc ed con d ition ➔ DD ↓ Nonsmok ers : No m ain ef fect cond it io n C: F ree conditio n ➔ DD – E1: Su g gested conditio n ➔ DD – E2: Fo rc ed con d ition ➔ DD – − Exp. 1 H C 7 2 (2 7 ) U nder g ra d u ates PR DD VIR, FDR 1 d– 46d WS −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s Kirby & Guastello (2001 ) Main ef fect con d ition C: F ree-linkin g co n d ition ➔ DD – E 1 : S ug g es te d -l in ki ng condition ➔ DD – E2: Impo sed-linking condition ➔ DD ↓ Exp. 2 H C 3 8 (1 2 ) U nder g ra d u ates PR DD VIR, FDR 7 d W S Main ef fect con d ition C: F ree-linkin g co n d ition ➔ DD – E 1 : S ug g es te d -l in ki ng condition ➔ DD ↓ E2: Impo sed-linking condition ➔ DD ↓↓ − Ti m e fr a m in g Dai & Fishb ach ( 2013 ) Exp. 1 H C 9 8 (4 8 ) College students PR DD FIR, FDR 3 d– 50d BS Main ef fect con d ition C1: Near -future condition ➔ DD – C2: Distant-future condition ➔ DD – E: W aitin g co n dition ➔ DD ↓ − Exp. 2a HC 157 (73) College students PR DD FIR, FDR 2 d– 40d BS Main ef fect con d ition C1: Near -future condition ➔ DD – C2: Distant-future condition ➔ DD – E: W aitin g co n dition ➔ DD ↓ − Exp. 2b HC 145 (– ) College students PR DD FIR, FDR 5 d– 45d BS Main ef fect con d ition C1: Near -future condition ➔ DD – C2: Distant-future condition ➔ DD – E: W aitin g condition ➔ DD ↓ − Exp. 3 H C 239 (128) College students PR DD FIR, FDR 6 d– 48d BS Main ef fect con d ition C: S h ort-wait ➔ DD – E: Lon g -wait ➔ DD ↓ − Exp. 4 H C 234 (87) College students PR DD FIR, FDR 6 d– 48d BS Main ef fect con d ition C: S h ort-wait ➔ DD – E: Lon g -wait ➔ DD ↓ − DeHart & Odum ( 2015 ) HC 76 (3 1 ) 21 HYP D D VIR, FDR 1 w –25 y B S Main ef fect con d ition C 1 :T em p o ra ld is ta n ce condition ➔ DD ↓ E1: T emporal distance condition (days )➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E2: S p ecif ic d ate condition ➔ DD ↓↓ Dshemuch ad se et al. ( 2013 ) HC 42 (1 4 ) 24.1 HYP D D VIR, VDR 1– 14 d W S Main ef fect con d ition C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ − Ebert & Prelec ( 20 0 7 ) Exp. 3 H C 121 (59) 22.2 HYP D D VIR, FDR 1 d– 1y BS Intera ctio n ef fect con d ition and fu ture time Near future: C: No focu s ➔ DD – E: T ime fo cu s ➔ DD ↓ Far future: C: No focu s ➔ DD ↓ E: T ime fo cu s ➔ DD – − Exp. 4 H C 218 (107) 21.1 HYP D D VIR, FDR 1 d– 1f8m BS Intera ctio n ef fect con d ition and fu ture time Near future: C: No focu s ➔ DD – E: T ime fo cu s ➔ DD ↓ Far future: C: No focu s ➔ DD ↓ E: T ime fo cu s ➔ DD – − Lempert et al. ( 20 1 6 ) HC 60 (2 6 ) 23.43 PR DD VIR, VDR 7d –180d WS No m ain ef fect cond it io n C: T emporal distance condition ➔ DD – E: Specific d ate co n dition ➔ DD – Main ef fect emotion al arous al for d elayed reward Low su b jective v alue delayed re w ard (low emotional ar ou sa l) : C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD – High subjective v alue delayed reward (high emotional aro u sal): C: T emporal distance condition ➔ DD ↓ E: Specific d ate condition ➔ DD ↓ − Klapproth ( 201 2 ) Su b stance abuse di so rd er / H C 30 (2 3 ) / 3 0 (9 ) 36.9 / 3 1 .3 HYP D D VIR, VDR 7– 18 6 d B S Main ef fect con d ition C: T emporal distance condition ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E: Specific d ate condition ➔ DD ↓ Intera ctio n ef fect con d ition and g roup In he al thy con tr o l gr ou p : C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD – In su b stance u se d isorder group : C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ LeBoeuf ( 2006 ) E xp. 1a HC 356 (– ) College students HYP F ITB – 3m –10 m B S Main ef fect con d ition C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ − Exp. 1b HC 240 (– ) College students HYP F ITB – 2m –18 m B S Main ef fect con d ition C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ − Exp. 2 H C 253 (– ) College students HYP F ITB VIR, VDR – BS Main ef fect con d ition C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ − Exp. 3 H C 8 6 (– ) College students HYP D D VIR, VDR 2m –23 m B S Main ef fect con d ition C: T emporal distance condition ➔ DD – E: Specific d ate condition ➔ DD ↓ − Rabino v ich et al. ( 20 1 0 ) E x p .2 H C 9 4( 3 0 ) 3 6( 2 0– 70) PR DD VIR, FDR 1 m –7m B S No m ain ef fect cond it io n C: S h ort-ter m time perspective ➔ DD – E: Lon g -ter m time perspective ➔ DD – Intera ctio n ef fect con d ition and attit u d es towards saving Negative att itu d e to w ar d s saving: C: S h ort-ter m time perspective ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E: Lon g -ter m time perspective ➔ DD – Positive attitude towards saving: C: S h ort-ter m time perspective ➔ DD – E: Lon g -ter m time perspective ➔ DD ↓ Read et al. ( 2005 ) Exp. 1 H C 9 0 (– ) College students HYP D D FIR, FDR 2 m –36 m B S Main ef fect con d ition C 1 :T em p o ra ld is ta n ce condition (days )➔ DD – C 2 :T em p o ra ld is ta n ce condition (month s) ➔ DD – E: Specific d ate condition ➔ DD ↓ − Exp. 2 H C 160 (-) College students HYP F ITB – 2m –36 m B S Main ef fect con d ition C: T emporal distance condition (month s) ➔ DD – E: Specific d ate co n dition ➔ DD ↓ − Exp. 3 H C 6 0 (– ) College students PR DD FIR, FDR 2 m –36 m B S Main ef fect con d ition C: T emporal distance condition (month s) ➔ DD – E: Specific d ate co n dition ➔ DD ↓ − Exp. 4 H C 9 0 (– ) College students HYP D D FIR, FDR 2 m –60 m B S Main ef fect con d ition C: T emporal distance condition (month s) ➔ DD – E1: T emporal distance (months) + specific d ate cond it io n ➔ DD – E2: Sp ecif ic d ate condition ➔ DD ↓ − Zauberman et al. ( 2009 ) Exp. 3 H C 190 (– ) College students HYP F ITB – 1m –3m B S No m ain ef fect cond it io n C: C o ntrol condition ➔ DD – E: Duration -p rim in g condition ➔ DD – Intera ctio n ef fect con d ition and time h o rizo n 1 m o n th tim e horizon : C: C o ntrol condition ➔ DD – E: Duration p riming condition ➔ DD ↓ 3 m o n th tim e horizon : C: C o ntrol condition ➔ DD ↓ E: Duration p riming condition ➔ DD ↓ − Reframing o f rewards Appelt et al. ( 201 1 ) Exp. 1 H C 607 (152) 37.51 HYP D D VIR, VDR 3m BS Main ef fect con d ition −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s C: Delay con d ition ➔ DD – E: Acceleration conditio n ➔ DD ↓ Exp. 2 H C 279 (84) 39.82 HYP D D VIR, VDR 3m BS Main ef fect con d ition C: Delay con d ition ➔ DD – E: Acceleration conditio n ➔ DD ↓ − Bickel, W ilson, et al. ( 2016 b ) Emotion manipulation as well HC 599 (383) 28.61 HYP D D FIR, FDR – BS Main ef fect con d ition C: Hid d en-zero co n dition ➔ DD – E: Exp lic it-zero conditio n ➔ DD ↓ Main ef fect con d ition (em o tion) C : N ega ti v e inc om e narra tiv e ➔ DD ↑ E1: Neu tr al income narra tiv e ➔ DD – E2: P o sitive in come narra tiv e ➔ DD – − Fassben d er et al. ( 20 1 4 ) Exp. 1 H C 4 2 (1 7 ) 22.4 PR D D V IR, VDR 7d –56d WS Main ef fect con d ition C: R o unded d ecimal condition ➔ DD – E: Non zer o d ecimal condition ➔ DD ↓ − Exp. 4 H C 183 (92) 35.5 HYP D D VIR, VDR 7d –56d BS Main ef fect con d ition C: R o unded d ecimal conditio n ➔ DD – E: Non zer o d ecimal conditio n ➔ DD ↓ − Exp. 5 A D H D / HC 25 (1 2 ) / 40 (2 3) 18.6 / 1 7 .6 PR DD VIR, VDR 7d –56d BS Main ef fect con d ition C: R o unded d ecimal conditio n ➔ DD – E: Non zer o d ecimal conditio n ➔ DD ↓ No inter actio n ef fect con d ition and g roup In he al thy con tr o l gr ou p : C; R o unded d ecimal conditio n ➔ DD – E: Non zer o d ecimal condition ➔ DD ↓ In ADH D g rou p : C: R o unded d ecimal condition ➔ DD – E: Non zer o d ecimal condition ➔ DD ↓ − Grace & McLean ( 2005 ) HC 24 (1 4 ) 24.9 HYP D D VIR, FDR 1 m –10 y W S Main ef fect con d ition C1: Baseline condition ➔ DD – E1: Delay con d ition ➔ DD ↓ −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E2: Accelerate condition ➔ DD ↓↓ Jiang et al. ( 2014 ) Exp. 1a HC 209 (55) 21.3 HYP D D VIR, FDR 1 w –4y B S Main ef fect con d ition C: P u re gain cond ition ➔ DD – E: Upfron t loss + g ain condition ➔ DD ↓ − Exp. 1b HC 106 (54) 22.5 HYP D D VIR, FDR 1 w –4y W S Main ef fect con d ition C: P u re gain cond ition ➔ DD – E: Upfron t loss + g ain condition ➔ DD ↓ − Exp. 2a HC 171 (82) 20.8 HYP D D VIR, FDR 1 w –4y B S Main ef fect con d ition C: P u re gain cond ition ➔ DD – E: Upfron t gain + g ain condition ➔ DD ↓ − Exp. 2b HC 103 (40) 21.5 HYP D D VIR, FDR 7 w –9y B S Main ef fect con d ition C: P u re gain cond ition ➔ DD – E: Upfron t loss + g ain condition ➔ DD ↓ − Exp. 2c HC 104 (61) 21.1 HYP D D VIR, FDR 3 w –4y W S Main ef fect con d ition C: P u re gain cond ition ➔ DD – E: Upfron t loss + g ain condition ➔ DD ↓ − Magen et al. ( 2008 ) Exp. 1 H C 1 12 (1 4 ) 33.7 HYP D D VIR, VDR 7d –140d BS Main ef fect con d ition C: Hid d en-zero condition ➔ DD – E: Exp lic it-zero condition ➔ DD ↓ − Exp. 2 H C 5 7 (1 3 ) 32.1 PR D D V IR, VDR 7d –140d BS Main ef fect con d ition C: Hid d en-zero co n dition ➔ DD – E: Exp lic it-zero conditio n ➔ DD ↓ − Magen et al. ( 20 1 4 ) Exp. 1 H C 182 (89) 35.66 PR DD VIR, VDR 7d –140d BS Main ef fect con d ition C: Hid d en-zero co n dition ➔ DD – E: Exp lic it-zero conditio n ➔ DD ↓ − Exp. 2 H C 2 3 (1 0 ) 27.5 PR D D V IR, VDR 7d –140d WS Main ef fect con d ition C: Hid d en-zero co n dition ➔ DD – E: Exp lic it-zero conditio n ➔ DD ↓ Radu et al. ( 201 1 ) Exp. 2 H C 47 (1 9 ) 18.8 (17 –2 2 ) HYP D D VIR, VDR 7d –140d WS Main ef fect con d ition C: Hid d en-zero co n dition ➔ DD – E: Exp lic it-zero conditio n ➔ DD ↓ − Read et al. ( 2013 ) Exp. 1 H C 373 (134) 36 HYP D D VIR, VDR 1y –3y BS Main ef fect con d ition C: Amo u nt condition ➔ DD – −
Ta b le 2 (continued ) Study Experiment Participants T ask Result on DD S eco ndary outcome Ty p e N (m al e) Age T ype R ewa rds D el ay s E: Interest-rate con d ition ➔ DD ↓ Exp. 2 H C 630 (252) 35 HYP D D VIR, VDR 1y-10 y BS Main ef fect con d ition (analyses without interest-rate cond ition) C 1 : N o inv es tm en t (NI ) Amount conditio n ➔ DD – C2: NI Interest-total condition ➔ DD – E 1 : In ve st m en t (I ) Am ou n t condition ➔ DD ↓ E2: I Interest-total condition ➔ DD ↓ − Exp. 3 H C 219 (99) 37 HYP D D VIR, VDR 1y –10y BS No m ain ef fect cond it io n C: Amo u nt condition ➔ DD – E1: Interest-rate co n d ition ➔ DD – E2: C o m posite condition ➔ DD – − W eatherly et al. ( 2010 ) HC 648 (207) 19.53 HYP F ITB – 1w –10 y B S Main ef fect con d ition C: W o n m oney conditio n ➔ DD – E: Owed m oney con d ition ➔ DD ↓ − W eatherly & Derenne (201 1 ) HC 156 (28) 21.20 1. HYP D D 2. HYP FITB 1. VIR, FDR 2. – 6m –10 y W S Main ef fect con d ition C: W o n m oney conditio n ➔ DD – E: Owed m oney con d ition ➔ DD ↓ − W eatherly & Te rr el l ( 2010 ) HC 177 (78) 19.66 HYP F ITB – 1w –10 y B S Main ef fect con d ition C: W o n m oney conditio n ➔ DD – E: Owed m oney con d ition ➔ DD ↓ − We b er et al. ( 20 0 7 ) Exp. 1 H C 176 (74) 38 PR DD VIR, VDR 3m BS Main ef fect con d ition C: Delay con d ition ➔ DD – E: Acceleration conditio n ➔ DD ↓ − Exp. 2 H C 1 12 (?) CDS V ir tua l-L ab volunteers PR DD VIR, VDR 3m BS Main ef fect con d ition C: Delay con d ition ➔ DD – E: Acceleration conditio n ➔ DD ↓ − Exp. 3 H C 8 9 (?) CDS V ir tua l-L ab volunteers PR DD VIR, VDR 3m BS Main ef fect con d ition C: Delay con d ition ➔ DD – E: Acceleration conditio n ➔ DD ↓ − Not e. HYP D D = hypothetical delay discounting task; P R DD = poten tially real delay d iscount ing task; REAL DD = real delay discounting task; HYP F ITB = hypothe ti ca l fil l-in-t he-b lan k task; P R F IT B = pot enti all y re al fil l-i n-t h e-blank ta sk; RE AL FI TB = re al fill in the b lank ta sk VI R = va ria b le im medi ate rew ard ; FIR = fixe d immedi ate rew ar d ; VDR = v ar iabl e d el ayed re wa rd; F DR = fixed de laye d rew ar d WS = w ithin subj ec t d esig n; BS = b et we en subje ct d es ign; E = exper iment al cond ition ; C = cont rol co nditi on; HC = h ea lt hy contr o ls ↓ = d elay dis counting d ecreased; ↑ = delay discounting increased; – = no changes in delay discounting
Regarding the studies evaluating the effects of manipula-tions on DD, 86% (n = 114) found the expected reducmanipula-tions in DD, 13% (n = 17) found null results or unexpected increases in DD and 1% (n = 1) found mixed results (i.e., only effects in healthy control group, not in amnestic patients). These results indicate that DD can be decreased, showing that DD is pro-foundly context dependent and changeable.
Trainings
Contingency management Contingency management (CM) is a well-researched and effective behavioral training to increase drug abstinence across substance-dependent disorders (Stanger et al.,2013). It promotes abstinence by delivering material incentives contingent on biochemically verified ab-stinence (Higgins, Silverman, & Heil,2008). Simply put, par-ticipants are paid for not using drugs. CM attempts to directly influence decision-making processes by shifting preferences for immediate rewards to delayed rewards (Stanger et al., 2013). Six studies examined the effect of a CM training, four studies included smokers (Kurti & Dallery,2014; Weidberg, Landes, García-Rodríguez, Yoon, & Secades-Villa,2015; Yi et al.,2008; Yoon, Higgins, Bradstreet, Badger, & Thomas, 2009), one study included opioid-dependent patients (Landes, Christensen, & Bickel, 2012), and one study included marijuana-dependent individuals (Peters, Petry, LaPaglia, Reynolds, & Carroll,2013). One study (16.5%) found expect-ed rexpect-eductions in DD, one found mixexpect-ed results on two different DD tasks (16.5%), and four found null results or unexpected increases in DD (67%). Regarding behavioral outcomes, four studies (67%) found significant reductions in smoking behav-ior. None of the studies tested whether decreases in substance use were mediated by decreases in DD rates.
The four studies that included smokers or treatment-seeking smokers examined effects on both DD and smoking behavior. Yi et al. (2008) included two DD tasks—one employing monetary rewards and one employing cigarette rewards. They found that monetary as well as cigarette DD was decreased in the CM condition, whereas no changes were found in the control condition. However, the CM condition was not directly compared with the control condition in the statistical analyses. Furthermore, a decrease in carbon monoxide (CO) levels, measuring how much carbon monoxide is present in the exhaled air of the smoker as a proxy of smoking behavior (Deveci, Deveci, Açik, & Ozan,2004) over time was found in the CM condition. Yet no results on CO levels were provided for the control condition, which did not allow a direct comparison between both conditions.
Yoon et al. (2009) performed two DD tasks, one including monetary rewards available immediately and after a delay. The other task included cigarette rewards available immediately and monetary rewards available after a delay.
They found attenuated DD in the CM condition on the task comparing monetary and cigarette rewards, but no effects on the monetary DD task. Moreover, participants in the CM condition had lower CO levels posttraining than participants in the control condition did. Weidberg et al. (2015) did not find direct effects of CM on DD, but they demonstrated an increase in smoking abstinence in the CM condition at posttest though not at follow-up. In a study by Kurti and Dallery (2014), CM and exercise were tested in several combinations to see what effects could be found on DD. Neither exercise nor CM decreased DD rates. However, the conditions including CM found increased latencies to smoke and decreased total puffs in smokers compared with conditions without CM.
Landes et al. (2012) found that DD decreased after a CM training in opioid-dependent patients; however, the control condition that only received buprenorphine also showed at-tenuated levels of DD. Peters et al. (2013) compared a CBT-only condition with three conditions including CM in marijuana-dependent individuals and found increases in DD in the CBT-only group, whereas DD rates remained stable in the CM conditions. Both studies did not find effects on mar-ijuana (Peters et al., 2013) and opioid use (Landes et al., 2012).
In summary, findings regarding CM and its ability to d e c r e a s e D D a r e m i x e d . S t u d ie s t h a t i n c l u d e d a substance-specific DD task (Yi et al., 2008; Yoon et al., 2009) yielded more positive effects than studies that used monetary DD tasks. The two studies with expected or mixed effects included a substance-specific DD task. These latter findings, in combination with the promising effects of CM on behavior (67%), could be an indication that the effects of CM are substance specific and do not transfer to monetary DD tasks. More research is needed to confirm whether DD functions as a mediator that reduces substance use by CM or whether other mechanisms are at work to explain the behavioral effects.
Money-management-based training Two studies exposed their participants to some sort of money-management-based training, based on the idea that more knowledge of money management increases the salience of future rewards and makes those more concrete. One study found null results for DD, but the expected results for cocaine abstinence; the other study found the expected reductions in DD. Black and Rosen (2011) allocated their participants either to the advisor-teller money manager (ATM) training condition—which is a multi-component training that includes substance abuse treatment in the context of discussions on other money-management concerns—or to a control condition. Patients in the ATM con-dition were stimulated to create monthly budgets that reflect long-term goals, broken down into short-term spending plans. The authors found that discounting rates increased and co-caine abstinence rates decreased in the control condition and
