Editing Flynn effect (section)

{{Short description|20th-century rise in intelligence test scores}}
{{Use mdy dates|date=January 2019}}
[[File:Ourworldindata wisc-iq-gains-over-time-flynn-2007.png|thumb|Composition of IQ Gains]]
The '''Flynn effect''' is the substantial and long-sustained increase in both [[fluid and crystallized intelligence]] test scores that were measured in many parts of the world over the 20th century, named after researcher [[James Flynn (academic)|James Flynn]] (1934–2020).<ref>{{Cite journal |last1=Trahan |first1=Lisa H. |last2=Stuebing |first2=Karla K. |last3=Fletcher |first3=Jack M. |last4=Hiscock |first4=Merrill |date=2014 |title=The Flynn effect: A meta-analysis. |journal=Psychological Bulletin |language=en |volume=140 |issue=5 |pages=1332–1360 |doi=10.1037/a0037173 |pmid=24979188 |pmc=4152423 |issn=1939-1455}}</ref><ref name=baker>{{Cite journal |last1=Baker |first1=David P. |last2=Eslinger |first2=Paul J. |last3=Benavides |first3=Martin |last4=Peters |first4=Ellen |last5=Dieckmann |first5=Nathan F. |last6=Leon |first6=Juan |date=March 2015 |title=The cognitive impact of the education revolution: A possible cause of the Flynn Effect on population IQ |journal=Intelligence |volume=49 |pages=144–58 |doi=10.1016/j.intell.2015.01.003 |issn=0160-2896}}</ref> When [[intelligence quotient]] (IQ) tests are initially [[Standard score#Standardizing in mathematical statistics|standardized]] using a [[Sample (statistics)|sample]] of test-takers, by convention the average of the test results is set to 100 and their [[standard deviation]] is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, usually born more recently than the first; the average result is set to 100. When the new test subjects take the older tests, in almost every case their average scores are significantly above 100.

Test score increases have been continuous and approximately linear from the earliest years of testing to the present. For example, a study published in the year 2009 found that British children's average scores on the [[Raven's Progressive Matrices]] test rose by 14 IQ points from 1942 to 2008.<ref>{{Cite journal |last=Flynn |first=James R. |date=March 2009 |title=Requiem for nutrition as the cause of IQ gains: Raven's gains in Britain 1938–2008 |journal=Economics and Human Biology |volume=7 |issue=1 |pages=18–27 |doi=10.1016/j.ehb.2009.01.009 |issn=1873-6130 |pmid=19251490}}</ref> Similar gains have been observed in many other countries in which IQ testing has long been widely used, including other Western European countries, as well as Japan and South Korea.<ref name=baker/> Improvements have also been reported for [[semantic memory|semantic]] and [[episodic memory]].<ref name="Rönnlund">{{cite journal |vauthors=Rönnlund M, Nilsson LG |title=Flynn effects on sub-factors of episodic and semantic memory: parallel gains over time and the same set of determining factors |journal=Neuropsychologia |volume=47 |issue=11 |pages=2174–80 |date=September 2009 |pmid=19056409 |doi=10.1016/j.neuropsychologia.2008.11.007 |s2cid=15706086 }}</ref> 

There are numerous proposed explanations of the Flynn effect, such as the rise in efficiency of education, along with skepticism concerning its implications. Some researchers have suggested the possibility of a mild reversal in the Flynn effect (i.e., a decline in IQ scores) in developed countries, beginning in the 1990s,<ref>{{cite journal | author = Al-Shahomee  | display-authors = etal | year = 2018 | title = An increase of intelligence in Libya from 2008 to 2017 | journal = Personality and Individual Differences | volume =  130| pages =  147–149| doi = 10.1016/j.paid.2018.04.004 | s2cid = 149095461 }}</ref><ref>{{Cite journal|doi = 10.1016/j.paid.2005.01.029|title = A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse|journal = Personality and Individual Differences|volume = 39|issue = 4|pages = 837–43|year = 2005|last1 = Teasdale|first1 = Thomas W|last2 = Owen|first2 = David R}}</ref><ref>{{Cite journal|doi = 10.1016/j.intell.2015.10.004|title = A reversal of the Flynn effect for spatial perception in German-speaking countries: Evidence from a cross-temporal IRT-based meta-analysis (1977–2014)|journal = Intelligence|volume = 53|pages = 145–53|year = 2015|last1 = Pietschnig|first1 = Jakob|last2 = Gittler|first2 = Georg}}</ref><ref name="pnas2018">{{Cite journal|last1=Bratsberg|first1=Bernt|last2=Rogeberg|first2=Ole|date=June 6, 2018|title=Flynn effect and its reversal are both environmentally caused|journal=Proceedings of the National Academy of Sciences|language=en|volume=115|issue=26|pages=6674–78|doi=10.1073/pnas.1718793115|issn=0027-8424|pmc=6042097|pmid=29891660|bibcode=2018PNAS..115.6674B |doi-access=free}}</ref> sometimes referred to as '''reverse Flynn effect'''. In certain cases, this apparent reversal may be due to cultural changes rendering parts of intelligence tests obsolete.<ref>{{cite journal |last1=Gonthier |first1=Corentin |last2=Grégoire |first2=Jacques |last3=Besançon |first3=Maud |title=No negative Flynn effect in France: Why variations of intelligence should not be assessed using tests based on cultural knowledge |journal=Intelligence |date=January 2021 |volume=84 |pages=101512 |doi=10.1016/j.intell.2020.101512|s2cid=230538271 |doi-access=free }}</ref> However, meta-analyses indicate that, overall, the Flynn effect continues, either at the same rate,<ref>{{cite journal |last1=Trahan |first1=Lisa H. |last2=Stuebing |first2=Karla K. |last3=Fletcher |first3=Jack M. |last4=Hiscock |first4=Merrill |title=The Flynn effect: A meta-analysis. |journal=Psychological Bulletin |date=2014 |volume=140 |issue=5 |pages=1332–1360 |doi=10.1037/a0037173|pmid=24979188 |pmc=4152423 }}</ref> or at a slower rate in developed countries.<ref>{{cite journal |last1=Pietschnig |first1=Jakob |last2=Voracek |first2=Martin |title=One Century of Global IQ Gains: A Formal Meta-Analysis of the Flynn Effect (1909–2013) |journal=Perspectives on Psychological Science |date=May 2015 |volume=10 |issue=3 |pages=282–306 |doi=10.1177/1745691615577701|pmid=25987509 |s2cid=12604392 }}</ref><ref>{{cite journal |last1=Wongupparaj |first1=Peera |last2=Kumari |first2=Veena|author2-link=Veena Kumari |last3=Morris |first3=Robin G. |title=A Cross-Temporal Meta-Analysis of Raven's Progressive Matrices: Age groups and developing versus developed countries |journal=Intelligence |date=March 2015 |volume=49 |pages=1–9 |doi=10.1016/j.intell.2014.11.008}}</ref>