Popular psychology in date order
About this timelineExperiments, books, companies and platforms that carried psychology into advertising, self-help, consumer research and feeds, in one continuous chronology. Open a record for the evidence, the limits and the matching textbook reading.
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1880 to 1919: suggestion and the first advertising psychology
- 1884 (link to this row)
The Nancy school: hypnosis as suggestion
At Nancy, Hippolyte Bernheim treated hypnosis as an effect of suggestion, against the Salpêtrière view of it as a pathological state. He learned the method from Ambroise-Auguste Liébeault. Bernheim's books of 1884 and 1886 set out the case.
Where it sits: Clinical psychology.
- 1895 (link to this row)
Le Bon's The Crowd
Gustave Le Bon's Psychologie des foules described crowds as moved by contagion, suggestion and unconscious motives. It was widely read, but it has no empirical method, rests on racial theory, and a modern reviewer says its theses have been largely abandoned.
Where it sits: Pop claim.
- 1900 (link to this row)
Harlow Gale's advertising questionnaires and trials
Harlow Gale sent an advertising questionnaire to about 200 firms in 1895 and ran laboratory trials with students. He reported both in a self-published paper in 1900 and linked repeated exposure to suggestion.
Where it sits: Academic psychology.
Read the record: Harlow Gale's advertising questionnaires and trials
- 1902 (link to this row)
James on healthy-mindedness and the mind-cure movement
In The Varieties of Religious Experience, William James described healthy-mindedness and the mind-cure movement as a type of religion. He described and interpreted the movement, and the passages read give quoted case reports, not controlled tests.
Where it sits: Academic psychology.
Read the record: James on healthy-mindedness and the mind-cure movement
- 1903 (link to this row)
Scott's The Theory of Advertising
Walter Dill Scott's The Theory of Advertising argued that advertising rests on psychology, and that people are suggestible, so a clear command works better than an argument. The book is mostly argument, with few tests.
Where it sits: Academic psychology.
- 1911March (link to this row)
Hollingworth's caffeine study for Coca-Cola and the Chattanooga trial
The Coca-Cola Company's attorneys hired Harry Hollingworth to test caffeine on 16 volunteers for the 1911 Chattanooga trial. The company financed the placebo-controlled, blinded 40-day study, which reported a genuine stimulant effect. It did not settle the legal question.
Where it sits: Academic psychology. Organizations: Coca-Cola.
Read the record: Hollingworth's caffeine study for Coca-Cola and the Chattanooga trial
- 1913 (link to this row)
Hollingworth's Advertising and Selling
Harry Hollingworth's 1913 book, which grew from lectures to New York advertising men, set out four tasks for an advertisement and tested appeals by ranking them in the laboratory and comparing the ranks with inquiry returns.
Where it sits: Academic psychology.
- 1913February (link to this row)
Watson's behaviorist manifesto
In a lecture published in Psychological Review in 1913, John B. Watson argued that psychology should be an objective natural science aiming at the prediction and control of behavior, with introspection set aside.
Where it sits: Academic psychology.
1920 to 1949: behaviorism, publicity and self-help
- 1920 (link to this row)
Watson and Rayner's Little Albert study
Watson and Rayner paired a white rat with a loud noise for one infant and reported that his fear spread to similar objects. The paper reports no follow-up or removal of the fear, and the identity of Albert B. is disputed.
Where it sits: Academic psychology.
- 1921 (link to this row)
Watson joins J. Walter Thompson
After leaving Johns Hopkins, John B. Watson worked at J. Walter Thompson until the mid-1930s. His field surveys, department tour and talks to business are documented. Credit for particular campaigns rests on secondary summaries, and the popular coffee-break credit is unsupported.
Where it sits: Consumer application. Organizations: J. Walter Thompson.
- 1922 (link to this row)
Coué and conscious autosuggestion
Émile Coué taught a fixed phrase about getting better, repeated daily. His 1922 English book and 1923 American tour brought press coverage and crowds. The sources show anecdotes and testimonials, and no controlled trials.
Where it sits: Pop claim.
- 1922 (link to this row)
Lippmann's Public Opinion
Walter Lippmann's Public Opinion argued that people act on mental pictures of a world they cannot see directly, shaped by stereotypes, and used the phrase manufacture of consent. It is political and press analysis that borrows psychology, not an experiment.
Where it sits: Pop claim.
- 1923 (link to this row)
Bernays, Freud and public relations
Edward Bernays was Freud's nephew, and the 1920 US edition of Freud's lectures carries a copyright line naming him. His own books cite group-mind writers more than Freud, and a recent scholar argues that the story of him applying Freud is a legend.
Where it sits: Pop claim.
- 1928 (link to this row)
Watson's Psychological Care of Infant and Child
Watson's 1928 child-care manual urged parents to avoid too much affection and to train children by conditioning. It sold well, but no source opened shows it changed what parents did, and official advice of the time was also strict.
Where it sits: Pop claim.
Read the record: Watson's Psychological Care of Infant and Child
- 1929March (link to this row)
The Easter Parade smokers of 1929 (torches of freedom)
Young women smoked in New York's 1929 Easter Parade in a stunt Edward Bernays staged for a tobacco client. Bernays's later account of its fame and of a psychoanalyst's advice is not matched by the press coverage described by historians.
Where it sits: Consumer application. Organizations: American Tobacco Company.
Read the record: The Easter Parade smokers of 1929 (torches of freedom)
- 1936 (link to this row)
Carnegie's How to Win Friends and Influence People
Dale Carnegie's 1936 book turned the principles of his adult public-speaking course into advice on handling people. Sales figures come from a newspaper review and company histories, not audits, and the book offers no experimental evidence.
Where it sits: Pop claim.
Read the record: Carnegie's How to Win Friends and Influence People
- 1943 (link to this row)
Maslow's hierarchy of needs and the pyramid he did not draw
Maslow's 1943 paper describes a hierarchy of needs in prose. The pyramid used in textbooks is not in that paper, and researchers interviewed in 2019 trace it to a 1960 management article. A later cross-cultural study links need fulfillment to well-being.
Where it sits: Pop claim.
Read the record: Maslow's hierarchy of needs and the pyramid he did not draw
- 1946 (link to this row)
Ernest Dichter and motivation research
From 1946 Ernest Dichter ran a consultancy selling depth-interview research to business and political clients. An archive documents the client list, but no source opened shows his advice worked, and a rival researcher and a trade-body glossary disputed his method.
Where it sits: Consumer application.
1950 to 1969: persuasion, conformity and motivation research
- 1951 (link to this row)
Asch's line-judgment studies
Asch asked male college students to match line lengths after a staged, unanimous majority gave wrong answers. The uninformed subjects erred on about a third of critical judgments, yet most answers stayed correct and a quarter of subjects never yielded.
Where it sits: Academic psychology.
- 1952 (link to this row)
Peale's The Power of Positive Thinking
Norman Vincent Peale's 1952 book was a long-running best-seller and drew criticism from clergy. It is a minister's advice, not an empirical program, and its sales figures come from the author, a publisher and press accounts.
Where it sits: Pop claim.
- 1953 (link to this row)
The Yale persuasion studies and Communication and Persuasion
A coordinated Yale project studied how the communicator affects opinion change, and Hovland, Janis and Kelley published Communication and Persuasion in 1953. In one experiment, source credibility changed opinion at first, but the gap closed within four weeks.
Where it sits: Academic psychology.
Read the record: The Yale persuasion studies and Communication and Persuasion
- 1957 (link to this row)
Festinger's theory of cognitive dissonance
Festinger proposed that people act to reduce the tension between cognitions that do not fit together. Brehm's choice experiment supported the theory, but later critics showed that the free-choice method can produce the same pattern without any change in preference.
Where it sits: Academic psychology.
- 1957 (link to this row)
Vicary's subliminal popcorn claim
In 1957 James Vicary said he had boosted popcorn and Coca-Cola sales in a cinema with messages flashed too briefly to see. He published no data, and a 1992 column says he later admitted his data were too small to be meaningful. The claim is unsupported.
Where it sits: Pop claim. Organizations: Coca-Cola.
- 1961 (link to this row)
Bandura's Bobo doll experiment
Preschool children who watched an adult attack an inflatable Bobo doll later copied much of that aggression in a new room. The study was small and short, used one nursery school, and shows nothing about advertising.
Where it sits: Academic psychology.
- 1962 (link to this row)
The Myers-Briggs Type Indicator moves into wide use
Katharine Briggs and Isabel Briggs Myers built a four-letter personality sorter drawing on Jung's types. Organizations and schools adopted it widely, while academic reviews question its type structure and reliability. Its publisher side disputes those criticisms.
Where it sits: Consumer application.
Read the record: The Myers-Briggs Type Indicator moves into wide use
- 1963 (link to this row)
Milgram's obedience experiment
At Yale, 26 of 40 men gave what they believed were shocks up to 450 volts when told to continue. The result is documented. Its ethics, its archive and its explanation as simple obedience are contested.
Where it sits: Academic psychology.
1970 to 1989: social learning, heuristics and consumer research
- 1971 (link to this row)
The Stanford prison experiment
In 1971 Zimbardo's team ran a mock prison with students as guards and prisoners and stopped it after six days. Critics using the archive say the guards were coached. The researchers now call it a one-trial demonstration, not a traditional experiment.
Where it sits: Academic psychology.
- 1974September (link to this row)
Tversky and Kahneman on heuristics and biases
Tversky and Kahneman described three judgment heuristics, representativeness, availability and anchoring, and argued that they produce systematic errors. Gigerenzer later criticized the program as vague. The paper reports demonstrations, not applications to business.
Where it sits: Academic psychology.
Read the record: Tversky and Kahneman on heuristics and biases
- 1979 (link to this row)
The McDonald's Happy Meal
McDonald's tested a boxed children's meal with a toy from 1977 and launched it across the United States in 1979. Press accounts disagree on who invented it. A 2012 FTC release covers food marketing to children in general and does not name McDonald's.
Where it sits: Consumer application. Organizations: McDonald’s.
- 1979March (link to this row)
Prospect theory and loss aversion
Kahneman and Tversky proposed that people judge outcomes as gains and losses from a reference point, with losses weighing more. The 1979 choice data are well documented. How general loss aversion is, and how far it explains consumer behavior, is disputed.
Where it sits: Academic psychology.
- 1981January (link to this row)
Framing: the Asian disease problem and price labels
Tversky and Kahneman showed in classroom questionnaires that describing the same outcomes as gains or as losses changed majority choices. The article also discussed a calculator price problem and credit-card price labels. Later work found framing effects vary by task.
Where it sits: Academic psychology.
Read the record: Framing: the Asian disease problem and price labels
- 1981May (link to this row)
American Airlines launches AAdvantage
American Airlines started AAdvantage on 1 May 1981, rewarding repeat flying with free travel. Earlier schemes existed, so 'first' depends on definition. Later experiments by Drèze and Nunes show how tier structure shapes perceived status.
Where it sits: Consumer application. Organizations: American Airlines.
- 1982June (link to this row)
The decoy (attraction) effect
Huber, Payne and Puto reported that adding a dominated option can raise the share of the option that dominates it. Two 2014 papers found no effect with natural stimuli. The popular Economist subscription example is a classroom test reported in a book review, with no source showing The Economist ran it.
Where it sits: Academic psychology.
- 1984 (link to this row)
Cialdini's Influence and the principles of persuasion
Robert Cialdini's Influence groups compliance research into a few principles. His company's examples are self-reported. A hotel towel experiment used to illustrate social proof was co-authored by Cialdini, and a 2014 test in two German hotels did not reproduce its advantage for descriptive norms.
Where it sits: Pop claim.
Read the record: Cialdini's Influence and the principles of persuasion
- 1985 (link to this row)
Thaler on mental accounting and transaction utility
Richard Thaler proposed that people code purchases and money in separate mental accounts and judge a deal by its price against a reference price. The evidence in the paper is questionnaire scenarios. Thaler won the 2017 economics prize.
Where it sits: Academic psychology.
Read the record: Thaler on mental accounting and transaction utility
- 1985April (link to this row)
New Coke and the return of Coca-Cola Classic
Coca-Cola changed its formula in April 1985 after taste tests that the company says involved nearly 200,000 people, then restored the original in July. The company says its tests missed attachment to the brand. Other readings differ.
Where it sits: Consumer application. Organizations: Coca-Cola, Pepsi.
Read the record: New Coke and the return of Coca-Cola Classic
- 1986 (link to this row)
The Elaboration Likelihood Model
The Elaboration Likelihood Model says persuasion works through careful thought or through simple cues, depending on how much people think. A 1983 student experiment with a fictitious razor brand found argument quality mattered under high involvement and endorsers under low involvement.
Where it sits: Academic psychology.
1990 to 2009: loyalty, nudges, neuromarketing and positive psychology
- 1995February (link to this row)
Tesco launches Clubcard
Tesco launched Clubcard in February 1995 after working with the data firm dunnhumby. Who deserves credit, and how much the card raised Tesco's fortunes, rests mostly on company-linked and press accounts. An independent Dutch study found a small effect of membership.
Where it sits: Consumer application. Organizations: Tesco.
- 2000 (link to this row)
Choice overload and the jam tasting study
Iyengar and Lepper found that more shoppers stopped at a 24-jam tasting booth but more bought after seeing 6 jams. A 2010 meta-analysis found a mean effect near zero across studies, and a 2015 meta-analysis found an overall effect once moderators were included.
Where it sits: Academic psychology.
- 2000January (link to this row)
Seligman and Csikszentmihalyi launch positive psychology
In January 2000 Seligman and Csikszentmihalyi introduced a special issue of American Psychologist on a science of positive experience, traits and institutions. Critics such as Lazarus and Held questioned its claims of novelty and its separatist message.
Where it sits: Academic psychology.
Read the record: Seligman and Csikszentmihalyi launch positive psychology
- 2003 (link to this row)
Fogg's Persuasive Technology and captology
B. J. Fogg's Stanford lab and 2003 book named persuasive technology, or captology, as a design field. Claims that its alumni built habit-forming apps are only partly supported: the sources show students and class output, not a causal line to any product's design.
Where it sits: Academic psychology.
- 2003November (link to this row)
Defaults in pension enrolment and organ-donation consent
Studies of pension enrollment and organ-donation consent found that the rule applying when people do nothing strongly shapes outcomes. Consent rates differ far more than actual donation rates, and the reasons are debated.
Where it sits: Academic psychology.
Read the record: Defaults in pension enrolment and organ-donation consent
- 2004 (link to this row)
The Coke and Pepsi brain-scan study and the Pepsi paradox
Academic researchers ran taste tests and brain scans with Coca-Cola and Pepsi, with and without brand cues. Brand knowledge changed stated preference and brain responses. The brands were stimuli. The funding statements read name a foundation and US health agencies, not either company.
Where it sits: Academic psychology. Organizations: Coca-Cola, Pepsi.
Read the record: The Coke and Pepsi brain-scan study and the Pepsi paradox
- 2004 (link to this row)
Held and Ehrenreich on the pressure to think positively
Barbara Held argued in 2002 and 2004 that positive thinking and positive psychology carry their own costs. According to a review, Barbara Ehrenreich's 2009 book made a wider case against positive thinking. These are arguments, not new experiments.
Where it sits: Academic psychology.
Read the record: Held and Ehrenreich on the pressure to think positively
- 2005 (link to this row)
The critical positivity ratio of 2.9013
Fredrickson and Losada (2005) reported a tipping-point ratio of 2.9013 positive to negative emotions. Brown, Sokal and Friedman (2013) said the mathematics behind it was unfounded. Fredrickson and Losada then withdrew the modeling, while Fredrickson argued other evidence still linked higher ratios to flourishing.
Where it sits: Academic psychology.
- 2006 (link to this row)
The endowed progress effect and the car wash loyalty card
Nunes and Drèze (2006) report that artificial head-start progress raised completion and shortened completion time. Secondary summaries place a loyalty card test at an unnamed car wash. The paper's completion percentages could not be checked and are not given.
Where it sits: Academic psychology.
Read the record: The endowed progress effect and the car wash loyalty card
- 2006February (link to this row)
The goal-gradient hypothesis and coffee loyalty cards
Kivetz, Urminsky and Zheng analyzed stamp-card purchases at a university cafe and found that customers bought faster as they neared a free coffee. The cafe is a campus cafe, not Starbucks or any chain.
Where it sits: Academic psychology.
Read the record: The goal-gradient hypothesis and coffee loyalty cards
- 2006February (link to this row)
The MusicLab artificial music market
In an artificial music market, 14,341 participants downloaded unknown songs. Seeing others' download counts made success more unequal and less predictable, though the best songs rarely did badly. Any link to feeds or charts is interpretation.
Where it sits: Academic psychology.
- 2006October (link to this row)
The Netflix Prize
Netflix released over 100 million ratings and offered one million dollars to any team that beat its Cinematch recommender by a further 10 percent. The contest framed recommending as predicting star ratings, a framing Netflix later moved away from.
Where it sits: Consumer application. Organizations: Netflix.
- 2007 (link to this row)
Grit as perseverance and passion for long-term goals
Duckworth and colleagues (2007) defined grit as perseverance and passion for long-term goals and reported that it predicted success beyond IQ and conscientiousness. A later meta-analysis found a corrected correlation of .84 with conscientiousness and only modest links to performance.
Where it sits: Academic psychology.
Read the record: Grit as perseverance and passion for long-term goals
- 2007August (link to this row)
Preschoolers taste the same food in McDonald's wrappers
Stanford researchers gave 63 preschoolers identical foods in McDonald's or plain wrappers. The original abstract reports an overall preference for branded samples. The brand was a stimulus; the study does not establish company intent or sponsorship. A later reassessment also points to packaging appearance.
Where it sits: Academic psychology. Organizations: McDonald’s.
Read the record: Preschoolers taste the same food in McDonald's wrappers
- 2008 (link to this row)
The learning styles meshing claim
A 2008 review found that people report learning preferences, but found virtually no evidence that matching teaching to a diagnosed style improves learning. A 2015 search of higher-education papers found most still endorsed learning styles.
Where it sits: Pop claim.
- 2008 (link to this row)
Starbucks Card Rewards and My Starbucks Rewards
Starbucks ran a card-based rewards scheme from 2008, merged it into My Starbucks Rewards in 2009 and in 2016 began awarding Stars by money spent. Membership and card-balance figures are the company's own reporting. No company document read cites a psychological theory.
Where it sits: Consumer application. Organizations: Starbucks.
Read the record: Starbucks Card Rewards and My Starbucks Rewards
- 2008April (link to this row)
Nudge: Thaler and Sunstein's book on choice architecture
Thaler and Sunstein's Nudge (2008) widely introduced the terms choice architecture and nudging. Reference works define a nudge as a predictable change in behavior without forbidden options. Philosophers raise autonomy objections. The book itself was not opened.
Where it sits: Academic psychology.
Read the record: Nudge: Thaler and Sunstein's book on choice architecture
- 2009October (link to this row)
New York City calorie labeling: Elbel and Dumanovsky studies
Two studies of New York City's 2008 menu calorie rule reached different results. Elbel's receipts study found no change in calories bought. Dumanovsky's surveys found no overall decline but falls at some chains, including McDonald's. Both studied customers, not McDonald's decisions.
Where it sits: Academic psychology. Organizations: McDonald’s.
Read the record: New York City calorie labeling: Elbel and Dumanovsky studies
2010 to 2026: feeds, recommenders and replication
- 2010 (link to this row)
The UK Behavioural Insights Team
The Behavioural Insights Team began as a unit embedded in UK government that argued for randomized trials of small changes to public services. It became a part-owned company in February 2014. This is government practice, not consumer marketing.
Where it sits: Academic psychology.
- 2010 (link to this row)
Harry Brignull names dark patterns
Designer Harry Brignull launched darkpatterns.org in 2010 to name deceptive interface designs. The term's history is documented; the psychology attached to it is researchers' interpretation, and a 2018 taxonomy grouped 118 practitioner examples into five strategies.
Where it sits: Consumer application.
- 2010 (link to this row)
Power posing: a small study, a TED talk and a failed replication
A 2010 study reported that expansive poses changed hormones and risk tolerance. A 2015 replication with a larger sample reported no such effects, and the first author later stated a belief that the effects are not real. An effect on felt power is the least disputed result.
Where it sits: Pop claim.
Read the record: Power posing: a small study, a TED talk and a failed replication
- 2010November (link to this row)
San Francisco's Happy Meal toy ordinance
In 2010 San Francisco passed an ordinance restricting toys with children's meals that exceeded nutrition limits. McDonald's opposed it. A later study of two unnamed chains found the toy sold for 10 cents extra and mixed effects on calories.
Where it sits: Consumer application. Organizations: McDonald’s.
- 2011 (link to this row)
Calorie posting at Starbucks: the Bollinger, Leslie and Sorensen study
Three economists used Starbucks transaction data from New York City, Boston and Philadelphia to measure what happened after mandatory calorie posting began in New York. Calories per transaction fell about 6 percent, mostly from food. The authors say they persuaded Starbucks to provide the data.
Where it sits: Academic psychology. Organizations: Starbucks.
Read the record: Calorie posting at Starbucks: the Bollinger, Leslie and Sorensen study
- 2011October (link to this row)
The iPhone op-ed and reverse inference in neuromarketing
A marketing writer's 2011 op-ed used unpublished brain-scan data to suggest people are in love with their iPhones. Neuroscientists replied that activity in one region is weak evidence for a specific feeling, and the sources opened do not support the love claim.
Where it sits: Pop claim.
Read the record: The iPhone op-ed and reverse inference in neuromarketing
- 2012 (link to this row)
Schüll's Addiction by Design and the slot machine analogy
Natasha Dow Schüll's 2012 ethnography of machine gambling in Las Vegas is academic work on casino design. Comparing social feeds to slot machines is a popular analogy, not a finding of the book, and an academic review cautions against the addiction frame.
Where it sits: Academic psychology.
Read the record: Schüll's Addiction by Design and the slot machine analogy
- 2012January (link to this row)
Berns and Moore: brain activity and later song sales
Berns and Moore scanned 27 adolescents listening to songs by mostly unknown artists and compared brain activity with the songs' sales over about three years. Ventral striatum activity correlated with sales (R = 0.32); stated liking did not.
Where it sits: Academic psychology.
Read the record: Berns and Moore: brain activity and later song sales
- 2014 (link to this row)
Facebook's emotional contagion experiment
Kramer, Guillory and Hancock (2014) filtered News Feed posts for 689,003 Facebook users for one week and counted emotional words in users' own posts. Effects were very small, and PNAS published an Expression of Concern about consent.
Where it sits: Academic psychology. Organizations: Facebook (Meta).
- 2015May (link to this row)
Bakshy, Messing and Adamic on news exposure on Facebook
Bakshy, Messing and Adamic (2015), described as Facebook data science researchers, used Facebook data on 10.1 million US users to compare friends, News Feed ranking and clicks as limits on cross-cutting news. Critics objected to the sample and to treating choice and ranking as rivals.
Where it sits: Academic psychology. Organizations: Facebook (Meta).
Read the record: Bakshy, Messing and Adamic on news exposure on Facebook
- 2015December (link to this row)
Netflix describes its recommender system and its business value
Two Netflix employees described the company's recommender, said it influences about 80 percent of streamed hours and estimated its value at over one billion dollars a year. These are company claims; the paper does not show how the estimate was made.
Where it sits: Consumer application. Organizations: Netflix.
Read the record: Netflix describes its recommender system and its business value
- 2016 (link to this row)
Deep Neural Networks for YouTube Recommendations
Covington, Adams and Sargin (2016) describe YouTube's two-stage recommender, whose ranking stage predicts expected watch time. The paper is a description of the 2016 system hosted by Google Research, not an independent audit.
Where it sits: Consumer application. Organizations: YouTube, Google.
Read the record: Deep Neural Networks for YouTube Recommendations
- 2017April (link to this row)
Netflix autoplay, "Are you still watching?" and sleep
Netflix can play the next episode automatically and asks "Are you still watching?" after a run of episodes. A survey links binge viewing to poorer sleep, but it is correlational and did not test Netflix features. No document opened shows design intent.
Where it sits: Consumer application. Organizations: Netflix.
Read the record: Netflix autoplay, "Are you still watching?" and sleep
- 2017December (link to this row)
Netflix chooses the artwork each member sees
Netflix posts describe testing several images per title and then choosing the image shown to each member from their viewing history. The performance claims are Netflix's own. In 2018 users alleged racial targeting; Netflix denied it.
Where it sits: Consumer application. Organizations: Netflix.
Read the record: Netflix chooses the artwork each member sees
- 2019 (link to this row)
Dark Patterns at Scale: a crawl of 11,000 shopping sites
Mathur and colleagues (2019) crawled about 11,000 shopping sites and found 1,818 dark pattern instances, on about 11.1 per cent of the sites. Luguri and Strahilevitz (2021) later showed in an online experiment that such patterns raised acceptance of a paid offer.
Where it sits: Academic psychology.
Read the record: Dark Patterns at Scale: a crawl of 11,000 shopping sites
- 2019 (link to this row)
Orben and Przybylski on screen time and adolescent well-being
Orben and Przybylski (2019) found a small negative association between technology use and adolescent well-being in three large datasets. Whether average associations are the right measure, and whether causal harm is shown, is disputed. This record gives no medical advice.
Where it sits: Academic psychology.
Read the record: Orben and Przybylski on screen time and adolescent well-being
- 2019 (link to this row)
YouTube radicalisation audits and YouTube's borderline content post
Studies disagree on whether YouTube's recommendations push viewers toward extreme content. Ribeiro and colleagues found movement from milder to more extreme channels, while Hosseinmardi and colleagues and Chen and colleagues found small, concentrated audiences and no systematic recommendation effect.
Where it sits: Academic psychology. Organizations: YouTube.
Read the record: YouTube radicalisation audits and YouTube's borderline content post
- 2020June (link to this row)
TikTok explains how the For You feed recommends videos
TikTok's own account of its For You feed lists three groups of signals and says strong signals count for more than weak ones. It is a company description, not an audit, and it gives no weights.
Where it sits: Consumer application. Organizations: TikTok.
Read the record: TikTok explains how the For You feed recommends videos
- 2022 (link to this row)
How large are nudge effects? Meta-analyses and nudge-unit trials
A 2022 meta-analysis of choice-architecture studies reported a pooled effect of d = 0.45. Critics said publication bias inflated it. A separate comparison found academic nudge papers showed larger effects than trials run by two government nudge units.
Where it sits: Academic psychology.
Read the record: How large are nudge effects? Meta-analyses and nudge-unit trials
- 2022January (link to this row)
Boeker and Urman's sock-puppet audit of TikTok personalization
Researchers ran scripted accounts on the TikTok website to test what changes the For You feed. Following a creator had the strongest effect. The abstract and main text disagree on the order of liking and watch time. This is a limited web audit, not a full test of the algorithm.
Where it sits: Academic psychology. Organizations: TikTok.
Read the record: Boeker and Urman's sock-puppet audit of TikTok personalization
- 2022September (link to this row)
FTC staff report on dark patterns and the EU Digital Services Act
In September 2022 FTC staff published Bringing Dark Patterns to Light, and the FTC release names four categories of deceptive design. The EU Digital Services Act has an Article 25 on deceptive interface design by online platforms. No case outcomes are stated here.
Where it sits: Consumer application.
Read the record: FTC staff report on dark patterns and the EU Digital Services Act
- 2023March (link to this row)
TikTok's default 60-minute prompt for under-18s
TikTok announced a default 60-minute daily limit for under-18s that a passcode can override. A state complaint, as reported, alleges its own test cut use by about 1.5 minutes a day. TikTok disputes the complaint. No independent evaluation was opened.
Where it sits: Consumer application. Organizations: TikTok.
Read the record: TikTok's default 60-minute prompt for under-18s
- 2023July (link to this row)
The Meta 2020 US election studies on feeds
Guess and colleagues (2023) moved consenting Facebook and Instagram users to chronological feeds in 2020 and found no significant change in polarization over three months. Critics question Meta's role and a temporary Meta algorithm change during the study window.
Where it sits: Academic psychology. Organizations: Facebook (Meta).
- 2024October (link to this row)
State lawsuits against TikTok and the Kentucky filing
US state attorneys general sued TikTok in October 2024. Kentucky's complaint, as reported, alleges an internal finding that habit forms after 260 videos. These are allegations. TikTok calls the quotes misleading and says it has safeguards.
Where it sits: Consumer application. Organizations: TikTok.
Read the record: State lawsuits against TikTok and the Kentucky filing
About this timeline
The timeline holds the same 81 records as the Directory, in date order. Each one separates what happened, the psychological idea, what is documented in practice, why it mattered and where the evidence stops. A label on every record says whether its core claim is documented, a company's own account, an independent experiment, an interpretation, contested or unsupported.How the evidence is labeled and checked.
Academic psychology, clinical psychology, consumer applications and popular claims are kept apart. A study that used a brand as a stimulus is not evidence that the brand used the finding. Where a record names a company, the page says what the sources document about that company and what they do not show.Coca-Cola, Starbucks, McDonald's, Netflix and TikTok.
Course connections use OpenStax Psychology 2e. They show where a topic sits in an introductory course and are not historical evidence.Course map. The site is a history and learning resource, offers no medical advice and has no tracker. Your text size choice is stored only in your browser.
Companion sites: Psy101 Timeline, a chronology of studies, ideas and events, and Psy101 People, profiles of psychologists and their precursors.