Research library
52 studies behind the ratings.
This library is the evidence base for every SuccessGuru rating and for the AI Guru. Each entry leads with the finding and links to the original paper or report.
Ratings that use a study link back here. The scoring rules are on the method page.
Summarizing 35 years of lab and field research, specific and difficult goals led to higher performance than vague "do your best" goals, especially with commitment, feedback, and adequate ability.
R01. Building a practically useful theory of goal setting and task motivation: A 35-year odyssey
Locke, E. A., & Latham, G. P. (2002). American Psychologist, 57(9), 705-717. Strong.
A guru who pushes specific, stretching goals is on solid ground; one who promises goals work by themselves, without feedback or skill, is not.
Across 94 independent tests, forming if-then plans ("If situation X, then I will do Y") had a medium-to-large effect on goal attainment (d = 0.65).
R02. Implementation intentions and goal achievement: A meta-analysis of effects and processes
Gollwitzer, P. M., & Sheeran, P. (2006). Advances in Experimental Social Psychology, 38, 69-119. Strong.
Cheap if-then planning is one of the best-supported tools a guru can teach; it does not require a paid program.
In 96 volunteers who repeated a new daily eating, drinking, or activity behavior for 12 weeks, the 39 whose data fit the model well took an estimated 18 to 254 days to reach 95% of their automaticity plateau (median 66 days); missing one opportunity did not materially affect the process.
R03. How are habits formed: Modelling habit formation in the real world
Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W., & Wardle, J. (2010). European Journal of Social Psychology, 40(6), 998-1009. Moderate.
Any guru selling a 21-day habit guarantee is wrong; expect roughly two months or more, and do not quit after a slip.
This theoretical review argues that habits are triggered automatically by context cues learned through repetition, largely independent of current goals or conscious intention.
R04. A new look at habits and the habit-goal interface
Wood, W., & Neal, D. T. (2007). Psychological Review, 114(4), 843-863. Moderate.
Changing your environment and cues tends to work better than relying on willpower, which many gurus overemphasize.
Across six samples, self-reported grit was associated with educational attainment, Ivy League GPA, West Point summer retention, and National Spelling Bee ranking, accounting for about 4% of variance in outcomes and adding modest prediction beyond IQ and conscientiousness.
R05. Grit: Perseverance and passion for long-term goals
Duckworth, A. L., Peterson, C., Matthews, M. D., & Kelly, D. R. (2007). Journal of Personality and Social Psychology, 92(6), 1087-1101. Contested.
Grit correlates with some achievements, but the original effects were modest, so treat grit-as-destiny claims with caution.
Pooling 88 samples (about 67,000 people), grit showed only modest correlations with performance and retention and was very strongly correlated with conscientiousness; the perseverance facet predicted better than passion.
R06. Much ado about grit: A meta-analytic synthesis of the grit literature
Credé, M., Tynan, M. C., & Harms, P. D. (2017). Journal of Personality and Social Psychology, 113(3), 492-511. Strong.
Grit is mostly an old trait with a new name, so programs promising to transform success by building grit oversell it.
Across two meta-analyses, the link between growth mindset and academic achievement was weak (r about 0.10), and mindset interventions had very small average effects (d about 0.08), with somewhat larger effects for low-income or academically at-risk students.
R07. To what extent and under which circumstances are growth mind-sets important to academic achievement? Two meta-analyses
Sisk, V. F., Burgoyne, A. P., Sun, J., et al. (2018). Psychological Science, 29(4), 549-571. Strong.
Mindset may help some struggling students a little, but it is not the life-changing lever many gurus claim.
In a nationally representative U.S. sample of ninth graders, a brief online growth-mindset program modestly raised grades among lower-achieving students (about 0.1 GPA points) and increased advanced math enrollment, with larger effects in supportive school settings.
R08. A national experiment reveals where a growth mindset improves achievement
Yeager, D. S., Hanselman, P., Walton, G. M., et al. (2019). Nature, 573(7774), 364-369. Strong.
A cheap, short intervention can nudge outcomes for some students, but the effect is small, not transformational.
Across 23 labs and more than 2,000 participants using a preregistered protocol, the ego-depletion effect (self-control as a depletable resource) was close to zero (d about 0.04).
R09. A multilab preregistered replication of the ego-depletion effect
Hagger, M. S., Chatzisarantis, N. L. D., Alberts, H., et al. (2016). Perspectives on Psychological Science, 11(4), 546-573. Failed to replicate.
Advice built on the idea that willpower is a fuel tank that runs out rests on shaky ground.
Among violinists and pianists, the best performers had accumulated far more hours of solitary, effortful deliberate practice than less accomplished peers, leading the authors to argue practice, not innate talent, drives expertise.
R10. The role of deliberate practice in the acquisition of expert performance
Ericsson, K. A., Krampe, R. T., & Tesch-Romer, C. (1993). Psychological Review, 100(3), 363-406. Contested.
Structured practice with feedback matters, but the popular 10,000-hour rule is a simplification the authors did not claim.
Across 88 studies, deliberate practice explained about 12% of performance differences overall: 26% in games, 21% in music, 18% in sports, 4% in education, and under 1% in professions.
R11. Deliberate practice and performance in music, games, sports, education, and professions: A meta-analysis
Macnamara, B. N., Hambrick, D. Z., & Oswald, F. L. (2014). Psychological Science, 25(8), 1608-1618. Strong.
Practice helps, but gurus who say anyone can master anything with enough hours ignore most of the variance.
This review of the author's research program found that positive fantasies about the future predict less effort and success, while mental contrasting (imagining the wish, then the obstacle) strengthens commitment when success is feasible.
R12. Future thought and behaviour change
Oettingen, G. (2012). European Review of Social Psychology, 23(1), 1-63. Moderate.
Pairing your dream with a hard look at obstacles (the WOOP method) beats pure positive visualization.
In four experiments, experimentally induced positive fantasies about an idealized future produced lower energy, measured by physiological and behavioral indicators, than fantasies that questioned the future, negative fantasies, or neutral fantasies.
R13. Positive fantasies about idealized futures sap energy
Kappes, H. B., & Oettingen, G. (2011). Journal of Experimental Social Psychology, 47(4), 719-729. Moderate.
Law-of-attraction style visualization may leave you feeling relaxed rather than ready to act.
Participants who could access tempting audiobooks only at the gym visited the gym more at first than controls, but the effect faded after a Thanksgiving break.
R14. Holding the Hunger Games hostage at the gym: An evaluation of temptation bundling
Milkman, K. L., Minson, J. A., & Volpp, K. G. M. (2014). Management Science, 60(2), 283-299. Moderate.
Pairing a treat with a chore can boost behavior short term, but it is not a permanent fix.
Google searches for "diet," gym visits, and goal-commitment contracts rose after temporal landmarks such as new weeks, months, years, birthdays, and holidays.
R15. The fresh start effect: Temporal landmarks motivate aspirational behavior
Dai, H., Milkman, K. L., & Riis, J. (2014). Management Science, 60(10), 2563-2582. Moderate.
Starting a change on a meaningful date can help, but the motivation boost is what matters, not the date itself.
In data from a debt settlement firm, closing debt accounts predicted eliminating debt regardless of the dollar balance of the accounts closed, while dollar balance did not predict debt elimination once the share of accounts closed was taken into account.
R16. Can small victories help win the war? Evidence from consumer debt management
Gal, D., & McShane, B. B. (2012). Journal of Marketing Research, 49(4), 487-501. Moderate.
Knocking out small debts first (the debt snowball) has real motivational support.
In four experiments using an incentivized debt-management game, people tended to pay off small debts first even though larger debts carried higher interest rates, which left them with more debt overall.
R17. Winning the battle but losing the war: The psychology of debt management
Amar, M., Ariely, D., Ayal, S., et al. (2011). Journal of Marketing Research, 48(SPL), S38-S50. Moderate.
The debt snowball may motivate, but it usually costs more in interest than paying the highest rate first.
In records of 66,465 U.S. households at a discount broker (1991 to 1996), the most active traders earned 11.4% a year versus 17.9% for the market, largely due to trading costs.
R18. Trading is hazardous to your wealth: The common stock investment performance of individual investors
Barber, B. M., & Odean, T. (2000). The Journal of Finance, 55(2), 773-806. Strong.
Gurus who push frequent trading are pushing a proven way to lose money relative to simply holding.
Among all individuals who began day trading Brazilian equity futures from 2013 to 2015, 97% of those who persisted more than 300 days lost money, and only 1.1% earned more than the minimum wage.
R19. Day trading for a living?
Chague, F., De-Losso, R., & Giovannetti, B. (2019). SSRN working paper 3423101. Strong.
Day trading course gurus are selling a path that almost everyone who follows it loses on.
About 65% of active U.S. large-cap funds trailed the S&P 500 in 2024, and about 90% trailed it over 15 years and 92% over 20 years.
R20. SPIVA U.S. Scorecard Year-End 2024
Ganti, A. R., Edwards, T., Di Gioia, D., Chapman, F., & Didio, N. (S&P Dow Jones Indices) (2025). S&P Dow Jones Indices report. Strong.
Low-cost index funds beat most professional stock pickers over the long run, so a guru promising to beat the market is betting against the odds.
Across 201 studies, financial education interventions explained only about 0.1% of the variance in financial behaviors, with weaker effects in low-income samples; effects decayed over time, and even large programs had negligible effects 20 months or more after the intervention.
R21. Financial literacy, financial education, and downstream financial behaviors
Fernandes, D., Lynch, J. G., Jr., & Netemeyer, R. G. (2014). Management Science, 60(8), 1861-1883. Strong.
A money course alone rarely changes behavior for long; just-in-time help and automatic systems matter more.
Using 1.7 million real-time experience samples from 33,391 employed U.S. adults, both momentary happiness and life satisfaction kept rising with log income, with no plateau at $75,000.
R22. Experienced well-being rises with income, even above $75,000 per year
Killingsworth, M. A. (2021). Proceedings of the National Academy of Sciences, 118(4), e2016976118. Strong.
Money does keep buying some extra well-being, but each doubling of income is needed for the same bump.
In an adversarial collaboration, happiness rose with income for most people, but for the least happy group (roughly the unhappiest 20%) it rose only up to about $100,000 and then plateaued.
R23. Income and emotional well-being: A conflict resolved
Killingsworth, M. A., Kahneman, D., & Mellers, B. (2023). Proceedings of the National Academy of Sciences, 120(10), e2208661120. Strong.
More money helps most people feel better, but it will not fix deep unhappiness.
Spending on others predicted greater happiness in a national survey and a field study of bonuses, and people randomly assigned to spend $5 or $20 on others were happier that evening than those told to spend on themselves.
R24. Spending money on others promotes happiness
Dunn, E. W., Aknin, L. B., & Norton, M. I. (2008). Science, 319(5870), 1687-1688. Moderate.
Giving is a cheap, evidence-backed happiness habit, no seminar needed.
Across 148 studies and more than 308,000 people, those with stronger social relationships had about 50% greater likelihood of survival over the study periods.
R25. Social relationships and mortality risk: A meta-analytic review
Holt-Lunstad, J., Smith, T. B., & Layton, J. B. (2010). PLoS Medicine, 7(7), e1000316. Strong.
Investing in relationships is as serious a health habit as many physical ones gurus promote.
Across a survey of 355 recently relocated adults and a study of 112 first-year college students, it took roughly 40 to 60 hours together to form a casual friendship, 80 to 100 hours to become a friend, and more than 200 hours to become a good friend.
R26. How many hours does it take to make a friend?
Hall, J. A. (2019). Journal of Social and Personal Relationships, 36(4), 1278-1296. Moderate.
Friendship takes sustained time, so hacks promising instant connection skip the main ingredient.
In 47 couples in their 80s from the Harvard Study of Adult Development, tracked over 8 days, those in more satisfying marriages stayed happier on days when they felt in poorer health.
R27. What's love got to do with it? Social functioning, perceived health, and daily happiness in married octogenarians
Waldinger, R. J., & Schulz, M. S. (2010). Psychology and Aging, 25(2), 422-431. Moderate.
Close relationships appear to buffer life's hard days, supporting relationship-focused advice.
The advisory reviewed research linking social disconnection to higher risk of early death, heart disease, stroke, dementia, depression, and anxiety, and called loneliness a public health concern.
R28. Our epidemic of loneliness and isolation: The U.S. Surgeon General's advisory on the healing effects of social connection and community
Office of the U.S. Surgeon General (2023). U.S. Department of Health and Human Services. Moderate.
Social connection is a health priority, not just a nice-to-have, which makes relationship advice worth taking seriously.
Commuters on Chicago-area trains and buses who were instructed to talk to a stranger reported a more positive ride than those told to sit in solitude, while separate commuters predicted the opposite.
R29. Mistakenly seeking solitude
Epley, N., & Schroeder, J. (2014). Journal of Experimental Psychology: General, 143(5), 1980-1999. Moderate.
Small talk with strangers is more rewarding than people expect, a cheap habit with support.
Across five studies, after conversations with strangers people consistently underestimated how much their partner liked them and enjoyed their company.
R30. The liking gap in conversations: Do people like us more than we think?
Boothby, E. J., Cooney, G., Sandstrom, G. M., & Clark, M. S. (2018). Psychological Science, 29(11), 1742-1756. Moderate.
You are probably more likable than you think, so fear of rejection should not stop you from connecting.
In 73 couples observed during a conflict discussion, those whose interactions were more negative than positive were more likely to consider dissolution and to separate about four years later.
R31. Marital processes predictive of later dissolution: Behavior, physiology, and health
Gottman, J. M., & Levenson, R. W. (1992). Journal of Personality and Social Psychology, 63(2), 221-233. Moderate.
The balance of positive to negative interactions matters, supporting some relationship-coaching advice.
In 130 newlywed couples, patterns such as the husband's rejection of the wife's influence and escalating negativity predicted later divorce, while de-escalation and positive affect predicted stability.
R32. Predicting marital happiness and stability from newlywed interactions
Gottman, J. M., Coan, J., Carrere, S., & Swanson, C. (1998). Journal of Marriage and the Family, 60(1), 5-22. Contested.
How couples handle conflict early matters, though precise divorce-prediction claims are overstated.
When interrupted during an email task, people completed work in less time with no loss of quality, but reported higher stress, frustration, time pressure, and effort.
R33. The cost of interrupted work: More speed and stress
Mark, G., Gudith, D., & Klocke, U. (2008). Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI 2008), 107-110. Moderate.
Interruptions have a real cost, mainly in stress, so protecting focus time is sensible advice.
In experiments, people who switched away from an unfinished task carried attention residue and performed worse on the next task; even finishing the first task reduced residue mainly when it was completed under time pressure.
R34. Why is it so hard to do my work? The challenge of attention residue when switching between work tasks
Leroy, S. (2009). Organizational Behavior and Human Decision Processes, 109(2), 168-181. Moderate.
Batching work and finishing tasks before switching has research behind it.
Heavy media multitaskers were more distracted by irrelevant information and, surprisingly, worse at task switching than light multitaskers.
R35. Cognitive control in media multitaskers
Ophir, E., Nass, C., & Wagner, A. D. (2009). Proceedings of the National Academy of Sciences, 106(37), 15583-15587. Contested.
Constant multitasking is not a skill that makes you better at juggling; it may reduce focus.
Among 340 outbound call center sales representatives, ambiverts (moderate extraversion) generated more revenue than either introverts or strong extraverts.
R36. Rethinking the extraverted sales ideal: The ambivert advantage
Grant, A. M. (2013). Psychological Science, 24(6), 1024-1030. Moderate.
You do not need to be a high-energy extravert to sell well, contrary to many sales gurus.
In 42 participants, holding expansive poses for two minutes was reported to raise testosterone, lower cortisol, and increase risk-taking and feelings of power.
R37. Power posing: Brief nonverbal displays affect neuroendocrine levels and risk tolerance
Carney, D. R., Cuddy, A. J. C., & Yap, A. J. (2010). Psychological Science, 21(10), 1363-1368. Failed to replicate.
The hormone and behavior claims behind power posing did not hold up, so do not pay for them.
In 200 participants (102 men, 98 women), power poses had no effect on testosterone, cortisol, or risk-taking, though participants reported feeling more powerful.
R38. Assessing the robustness of power posing: No effect on hormones and risk tolerance in a large sample of men and women
Ranehill, E., Dreber, A., Johannesson, M., et al. (2015). Psychological Science, 26(5), 653-656. Strong.
Power poses may nudge how you feel but do not change your body chemistry or behavior as claimed.
Repeating "I'm a lovable person" made people with low self-esteem feel worse, while it helped only those with already high self-esteem, and only slightly.
R39. Positive self-statements: Power for some, peril for others
Wood, J. V., Perunovic, W. Q. E., & Lee, J. W. (2009). Psychological Science, 20(7), 860-866. Moderate.
Affirmations may backfire for the very people gurus aim them at.
Across three studies, people assigned to list things they were grateful for reported somewhat higher well-being and more positive outlook than those listing hassles or neutral events.
R40. Counting blessings versus burdens: An experimental investigation of gratitude and subjective well-being in daily life
Emmons, R. A., & McCullough, M. E. (2003). Journal of Personality and Social Psychology, 84(2), 377-389. Moderate.
Gratitude journaling is a free, reasonably supported habit, though gains are modest.
The authors reported studies in which students who mentally rehearsed the steps to study for an exam studied more and performed better than students who visualized the outcome of getting a good grade.
R41. Harnessing the imagination: Mental simulation, self-regulation, and coping
Taylor, S. E., Pham, L. B., Rivkin, I. D., & Armor, D. A. (1998). American Psychologist, 53(4), 429-439. Moderate.
Visualize the process, not just the prize; outcome-only visualization is weak advice.
Across 138 studies, interventions that increased progress monitoring improved goal attainment (d about 0.40), with larger effects when progress was recorded physically or reported publicly.
R42. Does monitoring goal progress promote goal attainment? A meta-analysis of the experimental evidence
Harkin, B., Webb, T. L., Chang, B. P. I., et al. (2016). Psychological Bulletin, 142(2), 198-229. Strong.
Tracking your progress is one of the most reliable tactics, and it costs nothing.
Across 18 studies, coaching had significant positive effects on performance and skills, well-being, coping, work attitudes, and goal-directed self-regulation.
R43. Does coaching work? A meta-analysis on the effects of coaching on individual level outcomes in an organizational context
Theeboom, T., Beersma, B., & van Vianen, A. E. M. (2014). The Journal of Positive Psychology, 9(1), 1-18. Moderate.
Coaching can help, but this says nothing about whether a particular celebrity coach is effective.
Across 17 studies, workplace coaching had positive effects on organizational outcomes overall (about 0.36), with the largest effects on individual-level results and affective outcomes and smaller effects on skill-based outcomes.
R44. The effectiveness of workplace coaching: A meta-analysis of learning and performance outcomes from coaching
Jones, R. J., Woods, S. A., & Guillaume, Y. R. F. (2016). Journal of Occupational and Organizational Psychology, 89(2), 249-277. Moderate.
Structured workplace coaching has support; unregulated life coaching is less studied.
In 51 work teams at a manufacturing company, team psychological safety was associated with more learning behavior, which in turn was associated with better team performance.
R45. Psychological safety and learning behavior in work teams
Edmondson, A. (1999). Administrative Science Quarterly, 44(2), 350-383. Strong.
Leaders who make it safe to speak up are backed by evidence; fear-based leadership is not.
In an agent-based computer model, the most successful individuals were usually of average talent but lucky, not the most talented.
R46. Talent versus luck: The role of randomness in success and failure
Pluchino, A., Biondo, A. E., & Rapisarda, A. (2018). Advances in Complex Systems, 21(03n04), 1850014. Contested.
Guru success stories may owe more to luck than their methods, a key reason to be skeptical of survivorship tales.
This review of 104 studies found that cold water immersion may reduce body fat and improve insulin sensitivity, with possible cardiovascular and metabolic benefits, but concluded that many studies were small, varied, and inconclusive.
R47. Health effects of voluntary exposure to cold water: A continuing subject of debate
Espeland, D., de Weerd, L., & Mercer, J. B. (2022). International Journal of Circumpolar Health, 81(1), 2111789. Moderate.
Cold plunges are not proven cures, so claims of transformative benefits outrun the evidence.
The review found very little clinical evidence for commercial detox diets: a handful of small, methodologically flawed studies and no randomized controlled trials in humans.
R48. Detox diets for toxin elimination and weight management: A critical review of the evidence
Klein, A. V., & Kiat, H. (2015). Journal of Human Nutrition and Dietetics, 28(6), 675-686. Strong.
Detox programs sold by wellness gurus lack scientific support.
Reviewing experimental evidence, the authors found that a medium-to-large change in intentions produces only a small-to-medium change in behavior, and outlined why people fail to act on intentions.
R49. The intention-behavior gap
Sheeran, P., & Webb, T. L. (2016). Social and Personality Psychology Compass, 10(9), 503-518. Strong.
Getting motivated is not enough; strategies like if-then planning and monitoring bridge the gap.
The paper proposed that happiness is shaped by a genetic set point, circumstances, and intentional activities, famously estimating 50%, 10%, and 40%, and argued intentional activities offer the best route to lasting gains.
R50. Pursuing happiness: The architecture of sustainable change
Lyubomirsky, S., Sheldon, K. M., & Schkade, D. (2005). Review of General Psychology, 9(2), 111-131. Contested.
The popular "40% of happiness is in your control" claim comes from this paper and is an oversimplification.
In a national survey of 1,016 adults, including 601 current or former MLM participants, 47% of participants lost money, 27% made no money, and 25% made a profit, more than half of them under $5,000.
R51. Multilevel marketing: The research, risks and rewards
AARP Foundation (2018). AARP Foundation research report. Moderate.
Most people who join multilevel marketing schemes do not make money, so income claims by MLM gurus deserve suspicion.
Based on interviews with women, the study proposed that shame resilience involves recognizing shame triggers, critical awareness, reaching out to others, and speaking about shame.
R52. Shame resilience theory: A grounded theory study on women and shame
Brown, B. (2006). Families in Society, 87(1), 43-52. Moderate.
Useful ideas for discussion, but interview-based theory, not proof that the methods work.