Since the reproducibility of experiments is an essential part of the scientific method, the inability to replicate the studies of others has potentially grave consequences for many fields of science in which significant theories are grounded on unreproduceable experimental work.
The replication crisis has been particularly widely discussed in the field of psychology (and in particular, social psychology) and in medicine, where a number of efforts have been made to re-investigate classic results, and to attempt to determine both the validity of the results, and, if invalid, the reasons for the failure of replication.
- 1 General
- 2 Medicine
- 3 Psychology
- 4 Marketing
- 5 Causes of the crisis
- 6 Addressing the replication crisis
- 7 See also
- 8 References
- 9 Further reading
GeneralAccording to a 2016 poll of 1,500 scientists reported in the journal Nature, 70% of them failed to reproduce another scientist's experiments (50% failed to reproduce their own experiment). These numbers differ among disciplines:
- chemistry: 90% (60%),
- biology: 80% (60%),
- physics and engineering: 70% (50%),
- medicine: 70% (60%),
- Earth and environment science: 60% (40%).
MedicineOut of 49 medical studies from 1990–2003, with more than 1000 citations, 45 claimed that studied therapy was effective. Out of these studies, 16% were contradicted by subsequent studies, 16% inflated effectiveness of therapy and 24% were not replicated. Food and Drug Administration in 1977–90 found flaws in 10–20% of medical studies. In a paper published in 2012, Glenn Begley, a biotech consultant working at Amgen, and Lee Ellis, at the University of Texas, argued that only 11% of the pre-clinical cancer studies could be replicated.
A 2016 article by John Ioannidis, Professor of Medicine and of Health Research and Policy at Stanford University School of Medicine and a Professor of Statistics at Stanford University School of Humanities and Sciences, elaborated on "Why Most Clinical Research Is Not Useful". In the article Ioannidis laid out some the problems and called for reform, characterizing certain points for medical research to be useful again – one example he made was the need for medicine to be "Patient Centered" (e.g. in the form of the Patient-Centered Outcomes Research Institute) instead of the current practice to mainly take care of "the needs of physicians, investigators, or sponsors". Ioannidis is known for his research focus on science itself since the 2005 paper "Why Most Published Research Findings Are False".
PsychologyReplication failures are not unique to psychology and are found in all fields of science. However, several factors have combined to put psychology at the center of controversy. Much of the focus has been on the area of social psychology, although other areas of psychology such as clinical psychology have also been implicated.
Firstly, questionable research practices (QRPs) have been identified as common in the field. Such practices, while not intentionally fraudulent, involve capitalizing on the gray area of acceptable scientific practices or exploiting flexibility in data collection, analysis, and reporting, often in an effort to obtain a desired outcome. Examples of QRPs include selective reporting or partial publication of data (reporting only some of the study conditions or collected dependent measures in a publication), optional stopping (choosing when to stop data collection, often based on statistical significance of tests), p-value rounding (rounding p-values down to .05 to suggest statistical significance), file drawer effect (nonpublication of data), post-hoc storytelling (framing exploratory analyses as confirmatory analyses), and manipulation of outliers (either removing outliers or leaving outliers in a dataset to cause a statistical test to be significant). A survey of over 2,000 psychologists indicated that a majority of respondents admitted to using at least one QRP. False positive conclusions, often resulting from the pressure to publish or the author's own confirmation bias, are an inherent hazard in the field, requiring a certain degree of skepticism on the part of readers.
Secondly, psychology and social psychology in particular, has found itself at the center of several scandals involving outright fraudulent research, most notably the admitted data fabrication by Diederik Stapel as well as allegations against others. However, most scholars acknowledge that fraud is, perhaps, the lesser contribution to replication crises.
Third, several effects in psychological science have been found to be difficult to replicate even before the current replication crisis. For example the scientific journal Judgment and Decision Making has published several studies over the years that fail to provide support for the unconscious thought theory. Replications appear particularly difficult when research trials are pre-registered and conducted by research groups not highly invested in the theory under questioning.
These three elements together have resulted in renewed attention for replication supported by Kahneman. Scrutiny of many effects have shown that several core beliefs are hard to replicate. A recent special edition of the journal Social Psychology focused on replication studies and a number of previously held beliefs were found to be difficult to replicate. A 2012 special edition of the journal Perspectives on Psychological Science also focused on issues ranging from publication bias to null-aversion that contribute to the replication crises in psychology In 2015, the first open empirical study of reproducibility in Psychology was published, called the Reproducibility Project. Researchers from around the world collaborated to replicate 100 empirical studies from three top Psychology journals. Fewer than half of the attempted replications were successful at producing statistically significant results in the expected directions, though most of the attempted replications did produce trends in the expected directions.
Scholar James Coyne has recently written that many research trials and meta-analyses are compromised by poor quality and conflicts of interest that involve both authors and professional advocacy organizations, resulting in many false positives regarding the effectiveness of certain types of psychotherapy.
The replication crisis does not necessarily mean that psychology is unscientific. Rather this process is a healthy if sometimes acrimonious part of the scientific process in which old ideas or those that cannot withstand careful scrutiny are pruned, although this pruning process is not always effective. The consequence is that some areas of psychology once considered solid, such as social priming, have come under increased scrutiny due to failed replications. The British Independent newspaper wrote that the results of the reproducibility project show that much of the published research is just "psycho-babble".
Nobel laureate and professor emeritus in psychology Daniel Kahneman argued that the original authors should be involved in the replication effort because the published methods are often too vague. Some others scientists, like Dr. Andrew Wilson disagree and argue that the methods should be written down in detail. An investigation of replication rates in psychology in 2012 indicated higher success rates of replication in replication studies when there was author overlap with the original authors of a study  (91.7% successful replication rates in studies with author overlap compared to 64.6% success replication rates without author overlap).
Replication rates in psychologyA report by the Open Science Collaboration in August 2015 that was coordinated by Brian Nosek estimated the reproducibility of 100 studies in psychological science from three high-ranking psychology journals. Overall, 36% of the replications yielded significant findings (p value below .05) compared to 97% of the original studies that had significant effects. The mean effect size in the replications was approximately half the magnitude of the effects reported in the original studies.
The same paper examined the reproducibility rates and effect sizes by journal (Journal of Personality and Social Psychology [JPSP], Journal of Experimental Psychology: Learning, Memory, and Cognition [JEP:LMC], Psychological Science [PSCI]) and discipline (social psychology, cognitive psychology). Study replication rates were 23% for JPSP, 38% for JEP:LMC, and 38% for PSCI. Studies in the field of cognitive psychology had a higher replication rate (50%) than studies in the field of social psychology (25%).
An analysis of the publication history in the top 100 psychology journals between 1900 and 2012 indicated that approximately 1.6% of all psychology publications were replication attempts. Articles were considered a replication attempt if the term "replication" appeared in the text. A subset of those studies (500 studies) was randomly selected for further examination and yielded a lower replication rate of 1.07% (342 of the 500 studies [68.4%] were actually replications). In the subset of 500 studies, analysis indicated that 78.9% of published replication attempts were successful. The rate of successful replication was significantly higher when at least one author of the original study was part of the replication attempt (91.7% relative to 64.6%).
Highlighting the social structure that discourages replication in psychology, Brian D. Earp and Jim A. C. Everett enumerated five points as to why replication attempts are uncommon
- "Independent, direct replications of others’ findings can be time-consuming for the replicating researcher
- "[Replications] are likely to take energy and resources directly away from other projects that reflect one’s own original thinking
- "[Replications] are generally harder to publish (in large part because they are viewed as being unoriginal)
- "Even if [replications] are published, they are likely to be seen as 'bricklaying' exercises, rather than as major contributions to the field
- "[Replications] bring less recognition and reward, and even basic career security, to their authors"
MarketingMarketing is another discipline with a "desperate need for replication". In addition to the previously mentioned arguments, replications studies in marketing are needed to examine the applicability of theories and models across countries and cultures, which is especially important because of possible influences of globalization.
Causes of the crisisIn a work published in 2015 Glenn Begley and John Ioannidis offer five bullets as to summarize the present predicaments:
- Generation of new data/ publications at an unprecedented rate.
- Compelling evidence that the majority of these discoveries will not stand the test of time.
- Causes: failure to adhere to good scientific practice & the desperation to publish or perish.
- This is a multifaceted, multistakeholder problem.
- No single party is solely responsible, and no single solution will suffice.
Philosopher and historian of Science Jerome R. Ravetz predicted in his 1971 book Scientific knowledge and its social problems that science – in moving from the little science made of restricted communities of scientists to big science or techno-science – would suffer major problems in its internal system of quality control. Ravetz anticipated that modern science's system of incentive might become dysfunctional (the present 'publish or perish' challenge). For Ravetz quality in science is maintained when there is a community of scholars linked by norms and standards, and a willingness to stand by these.
Historian Philip Mirowski offered more recently a similar diagnosis in his 2011 book Science Mart (2011). 'Mart' is here a reference to the retail giant 'Walmart' and an allusion to the commodification of science. In the analysis of Mirowski when science becomes a commodity being traded in a market its quality collapses. Mirowski argues his case by tracing the decay of science to the decision of major corporations to close their in house laboratories in order to outsource their work to universities, and subsequently to move their research away from universities to even cheaper contract research organization (CRO).
The crisis of science's quality control system is affecting the use of science for policy. This is the thesis of a recent work by a group of STS scholars, who identify in 'evidence based (or informed) policy' a point of present tension.
Addressing the replication crisisReplication has been referred to as "the cornerstone of science". Replication studies attempt to evaluate whether published results reflect true findings or false positives. The integrity of scientific findings and reproducibility of research are important as they form the knowledge foundation on which future studies are built.
Tackling publication bias with pre-registration of studiesA recent innovation in scientific publishing to address the replication crisis is through the use of registered reports. The registered report format requires authors to submit a description of the study methods and analyses prior to data collection. Once the method and analysis plan is vetted through peer-review, publication of the findings is provisionally guaranteed, based on whether the authors follow the proposed protocol. One goal of registered reports is to circumvent the publication bias toward significant findings that can lead to implementation of QRPs and to encourage publication of studies with rigorous methods.
The journal Psychological Science has encouraged the preregistration of studies and the reporting of effect sizes and confidence intervals. The editor in chief also noted that the editorial staff will be asking for replication of studies with surprising findings from examinations using small sample sizes before allowing the manuscripts to be published.
Emphasizing replication attempts in teachingBased on coursework in experimental methods at MIT and Stanford, it has been suggested that methods courses in psychology emphasize replication attempts rather than original studies. Such an approach would help students learn scientific methodology and provide numerous independent replications of meaningful scientific findings that would test the replicability of scientific findings. Some have recommended that graduate students should be required to publish a high-quality replication attempt on a topic related to their doctoral research prior to graduation.
Encouraging use of larger sample sizesTo improve the quality of replications, larger sample sizes than those used in the original study are often needed. Larger sample sizes are needed because estimates of effect sizes in published work are often exaggerated due to publication bias and large sampling variability associated with small sample sizes in an original study.
Sharing raw data in online repositoriesOnline repositories where data, protocols, and findings can be stored and evaluated by the public seek to improve the integrity and reproducibility of research. Examples of such repositories include the open science framework, http://www.re3data.org/, and www.psychfiledrawer.org. Sites like Open Science Framework offer badges for using open science practices in an effort to incentivize scientists. However, there has been concern that those who are most likely to provide their data and code for analyses are the researchers that are likely the most sophisticated. John Ioannidis at Stanford University suggested that "the paradox may arise that the most meticulous and sophisticated and method-savvy and careful researchers may become more susceptible to criticism and reputation attacks by reanalyzers who hunt for errors, no matter how negligible these errors are".
Funding for replication studiesIn July 2016 the Netherlands Organisation for Scientific Research made 3 million Euros available for replication studies. The funding is for replication based on reanalysis of existing data and replication by collecting and analysing new data. Funding is available in the areas of social sciences, health research and healthcare innovation.
In 2013 the Laura and John Arnold Foundation funded the launch of The Center for Open Science with a $5.25 million grant and by 2017 had provided an additional $10 million in funding. It also funded the launch of the Meta-Research Innovation Center at Stanford at Stanford University run by John Ioannidis and Steven Goodman to study ways to improve scientific research. It also provided funding for the AllTrials initiative led in part by Ben Goldacre.
- Invalid science
- Publication bias
- Center for Open Science
- Reproducibility Project
- Science Wars
- Schooler, J. W. (2014). "Metascience could rescue the 'replication crisis'". Nature. 515 (7525): 9. doi:10.1038/515009a.
- Gary Marcus (May 1, 2013). "The Crisis in Social Psychology That Isn't". The New Yorker.
- Jonah Lehrer (December 13, 2010). "The Truth Wears Off". The New Yorker.
- Baker, Monya (26 May 2016). "1,500 scientists lift the lid on reproducibility". Nature. 533 (7604): 452–454. doi:10.1038/533452a.
- Fanelli, Daniele (29 May 2009). "How Many Scientists Fabricate and Falsify Research? A Systematic Review and Meta-Analysis of Survey Data". PLOS ONE. 4 (5): e5738. doi:10.1371/journal.pone.0005738. PMC . PMID 19478950 – via PLoS Journals.
- Ioannidis JA (13 July 2005). "COntradicted and initially stronger effects in highly cited clinical research". JAMA. 294 (2): 218–228. doi:10.1001/jama.294.2.218. PMID 16014596 – via Silverchair.
- Glick, J. Leslie (1 January 1992). "Scientific data audit—A key management tool". Accountability in Research. 2 (3): 153–168. doi:10.1080/08989629208573811 – via Taylor and Francis+NEJM.
- Begley, C. G., and Lee M. E., 2012, Drug Development: Raise Standards for Preclinical Cancer Research, Nature, 483, 531–533.
- Begley, C.G., 2013, Reproducibility: Six red flags for suspect work, Nature, 497, 433–434.
- Ioannidis, JPA (2016). "Why Most Clinical Research Is Not Useful". PLoS Med. 13 (6): e1002049. doi:10.1371/journal.pmed.1002049.
- Ioannidis, John P. A. (August 1, 2005). "Why Most Published Research Findings Are False". PLoS Medicine. 2 (8): e124. doi:10.1371/journal.pmed.0020124. ISSN 1549-1277. PMC . PMID 16060722.
- Achenbach, Joel. "No, science's reproducibility problem is not limited to psychology". The Washington Post. Retrieved 10 September 2015.
- John, Leslie K.; Loewenstein, George; Prelec, Drazen (2012-05-01). "Measuring the Prevalence of Questionable Research Practices With Incentives for Truth Telling". Psychological Science. 23 (5): 524–532. doi:10.1177/0956797611430953. ISSN 0956-7976. PMID 22508865.
- "The Nine Circles of Scientific Hell". Perspectives on Psychological Science. 7 (6): 643–644. 2012-11-01. doi:10.1177/1745691612459519. ISSN 1745-6916. PMID 26168124.
- "Research misconduct - The grey area of Questionable Research Practices". www.vib.be. Retrieved 2015-11-13.
- Fiedler, Klaus; Schwarz, Norbert (2015-10-19). "Questionable Research Practices Revisited". Social Psychological and Personality Science. 7: 1948550615612150. doi:10.1177/1948550615612150. ISSN 1948-5506.
- Simmons, Joseph; Nelson, Leif; Simonsohn, Uri (November 2011). "False-Positive Psychology: Undisclosed Flexibility in Data Collection and Analysis Allows Presenting Anything as Significant". Psychological Science. Washington DC: Association for Psychological Science. 22 (11): 1359–1366. doi:10.1177/0956797611417632. ISSN 0956-7976. PMID 22006061. Retrieved 29 January 2012.
- Shea, Christopher (13 November 2011). "Fraud Scandal Fuels Debate Over Practices of Social Psychology" – via The Chronicle of Higher Education.
- Kahneman, Daniel. "A New Etiquette for Replication" – via Scribd.
- [dead link]
- Table of Contents
- Open Science Collaboration (2015). "Estimating the reproducibility of Psychological Science". Science. 349 (6251): aac4716. doi:10.1126/science.aac4716. PMID 26315443.
- Coyne, James (April 15, 2014). "Are meta analyses conducted by professional organizations more trustworthy?". Mind the Brain. Retrieved September 13, 2016.
- Meyer, Michelle N.; Chabris, Christopher (31 July 2014). "Why Psychologists' Food Fight Matters" – via Slate.
- "Psychology Is Starting To Deal With Its Replication Problem". 27 August 2015.
- "Science Isn't Broken". 19 August 2015.
- Etchells, Pete (28 May 2014). "Psychology's replication drive: it's not about you" – via The Guardian.
- Wagenmakers, Eric-Jan; Wetzels, Ruud; Borsboom, Denny; Maas, Han L. J. van der; Kievit, Rogier A. (2012-11-01). "An Agenda for Purely Confirmatory Research". Perspectives on Psychological Science. 7 (6): 632–638. doi:10.1177/1745691612463078. ISSN 1745-6916. PMID 26168122.
- Ioannidis, John P. A. (2012-11-01). "Why Science Is Not Necessarily Self-Correcting". Perspectives on Psychological Science. 7 (6): 645–654. doi:10.1177/1745691612464056. ISSN 1745-6916. PMID 26168125.
- Pashler, Harold; Harris, Christine R. (2012-11-01). "Is the Replicability Crisis Overblown? Three Arguments Examined". Perspectives on Psychological Science. 7 (6): 531–536. doi:10.1177/1745691612463401. ISSN 1745-6916. PMID 26168109.
- Bartlett, Tom (30 January 2013). "Power of Suggestion" – via The Chronicle of Higher Education.
- Connor, Steve (27 August 2015). "Study reveals that a lot of psychology research really is just 'psycho-babble'". The Independent. London.
- Chambers, Chris (10 June 2014). "Physics envy: Do 'hard' sciences hold the solution to the replication crisis in psychology?" – via The Guardian.
- Makel, Matthew C.; Plucker, Jonathan A.; Hegarty, Boyd (2012-11-01). "Replications in Psychology Research How Often Do They Really Occur?". Perspectives on Psychological Science. 7 (6): 537–542. doi:10.1177/1745691612460688. ISSN 1745-6916. PMID 26168110.
- Collaboration, Open Science (2015-08-28). "Estimating the reproducibility of psychological". Science. 349 (6251): aac4716. doi:10.1126/science.aac4716. ISSN 0036-8075. PMID 26315443.
- see also Earp and Trafimow, 2015
- Everett, Jim Albert Charlton; Earp, Brian D. (2015-01-01). "A tragedy of the (academic) commons: interpreting the replication crisis in psychology as a social dilemma for early-career researchers". Frontiers in Psychology. 6: 1152. doi:10.3389/fpsyg.2015.01152. PMC . PMID 26300832.
- "Resolving the replication crisis in social psychology? A new proposal | SPSP". www.spsp.org. Retrieved 2015-11-18.
- Hunter, John E. (2011-06-01). "The desperate need for replications". Journal of Consumer Research. 28 (1): 149–158. doi:10.1086/321953.
- Aichner, Thomas; Coletti, Paolo; Forza, Cipriano; Perkmann, Urban; Trentin, Alessio (2016-03-22). "Effects of Subcultural Differences on Country and Product Evaluations: A Replication Study". Journal of Global Marketing. 29 (3): 115–127. doi:10.1080/08911762.2015.1138012.
- Begley, C. G. & Ioannidis, J. P. (2015). "Reproducibility in Science: Improving the Standard for Basic and Preclinical Research". Circulation Research. 116 (1): 116–126. doi:10.1161/CIRCRESAHA.114.303819. PMID 25552691.
- De Solla Price; Derek J. (1963). Little science big science. Columbia University Press.
- Siebert, S.; Machesky, L. M. & Insall, R. H. (2015). "Overflow in science and its implications for trust". eLife. 4: e10825. doi:10.7554/eLife.10825. PMC . PMID 26365552.
- Della Briotta Parolo, P.; Kumar Pan; R. Ghosh; R. Huberman; B.A. Kimmo Kaski; Fortunato, S. (2015). "Attention decay in science". Journal of Informetrics. 9 (4): 734–745. arXiv: . doi:10.1016/j.joi.2015.07.006.
- Mirowski, P. (2011). Science-Mart: Privatizing American Science. Harvard University Press.
- Benessia, A., Funtowicz, S., Giampietro, M., Guimarães Pereira, A., Ravetz, J., Saltelli, A., Strand, R., van der Sluijs, J., 2016. The Rightful Place of Science: Science on the Verge. The Consortium for Science, Policy and Outcomes at Arizona State University.
- Andrea Saltelli; Jerome R. Ravetz & Silvio Funtowicz (25 June 2016). "A new community for science". New Scientist. No. 3079. p. 52.
- Moonesinghe, Ramal; Khoury, Muin J; Janssens, A. Cecile J. W (2007-02-27). "Most Published Research Findings Are False—But a Little Replication Goes a Long Way". PLoS Med. 4 (2): e28. doi:10.1371/journal.pmed.0040028. PMC . PMID 17326704.
- Simons, Daniel J. (2014-01-01). "The Value of Direct Replication". Perspectives on Psychological Science. 9 (1): 76–80. doi:10.1177/1745691613514755. ISSN 1745-6916. PMID 26173243.
- "Registered Replication Reports - Association for Psychological Science". www.psychologicalscience.org. Retrieved 2015-11-13.
- Chambers, Chris. "Psychology's 'registration revolution' | Chris Chambers". the Guardian. Retrieved 2015-11-13.
- Lindsay, D. Stephen (2015-11-09). "Replication in Psychological Science". Psychological Science. 26: 0956797615616374. doi:10.1177/0956797615616374. ISSN 0956-7976. PMID 26553013.
- Frank, Michael C.; Saxe, Rebecca (2012-11-01). "Teaching Replication". Perspectives on Psychological Science. 7 (6): 600–604. doi:10.1177/1745691612460686. ISSN 1745-6916. PMID 26168118.
- Grahe, Jon E.; Reifman, Alan; Hermann, Anthony D.; Walker, Marie; Oleson, Kathryn C.; Nario-Redmond, Michelle; Wiebe, Richard P. (2012-11-01). "Harnessing the Undiscovered Resource of Student Research Projects". Perspectives on Psychological Science. 7 (6): 605–607. doi:10.1177/1745691612459057. ISSN 1745-6916. PMID 26168119.
- Maxwell, Scott E.; Lau, Michael Y.; Howard, George S. "Is psychology suffering from a replication crisis? What does "failure to replicate" really mean?". American Psychologist. 70 (6): 487–498. doi:10.1037/a0039400.
- IntHout, Joanna; Ioannidis, John P.A.; Borm, George F.; Goeman, Jelle J. "Small studies are more heterogeneous than large ones: a meta-meta-analysis". Journal of Clinical Epidemiology. 68 (8): 860–869. doi:10.1016/j.jclinepi.2015.03.017.
- Button, Katherine S.; Ioannidis, John P. A.; Mokrysz, Claire; Nosek, Brian A.; Flint, Jonathan; Robinson, Emma S. J.; Munafò, Marcus R. (2013-05-01). "Power failure: why small sample size undermines the reliability of neuroscience". Nature Reviews Neuroscience. 14 (5): 365–376. doi:10.1038/nrn3475. ISSN 1471-003X.
- Greenwald, Anthony G. "Consequences of prejudice against the null hypothesis.". Psychological Bulletin. 82 (1): 1–20. doi:10.1037/h0076157.
- Ioannidis, John P.A. "Anticipating consequences of sharing raw data and code and of awarding badges for sharing". Journal of Clinical Epidemiology. doi:10.1016/j.jclinepi.2015.04.015.
- "NWO makes 3 million available for Replication Studies pilot". NWO. Retrieved 2 August 2016.
- Apple, Sam (January 22, 2017). "The Young Billionaire Behind the War on Bad Science". Wired.
- 1,500 scientists lift the lid on reproducibility, Nature.com
- November 2012 special edition of Perspectives on Psychological Science on the issues of replicability and research practices in psychology
- Reproducibility in Science: Improving the Standard for Basic and Preclinical Research
- Social, Behavioral, and Economic Sciences Perspectives on Robust and Reliable Science
- Why Most Published Research Findings Are False
- Bonett, DG (2012) Replication-extension studies. Current Directions in Psychology 21, 409-412.
- Most scientific studies are wrong, but that doesn’t mean what you think it means - The Logic of Science
- Article on The Conversation (website) Science in crisis: from the sugar scam to Brexit, our faith in experts is fading, September 26, 2016