The Flynn Effect – Explaining Increasing IQ Scores

The Flynn Effect refers to the finding that the average human IQ has increased over time, which was first discovered by researcher James Flynn in 1984.

The actual term “Flynn Effect” was created by Herrnstein and Murray in 1994 to refer to James Flynn’s findings of this increase in IQ over time (Williams, 2013; Herrnstein & Murray, 2010).

In his groundbreaking paper, Flynn found evidence “that representative samples of Americans did better and better on IQ tests over a period of 46 years, the total gain amounting to a rise in mean IQ of 13.8 points” (Flynn, 1984).

With the assumption that IQ tests are an accurate representation of intelligence, this result indicates an increase in human intelligence over time.

As Flynn discussed in his Ted Talk in 2013, human civilization has seen a big increase in IQ over time, as every generation gets more and more questions right on IQ tests (Flynn, 2013).  He explains that “if you score the people a century ago against modern norms, they would have an average IQ of 70.  If you score us against their norms, we would have an average IQ of 130” (Flynn, 2013).

Interestingly, there has been the biggest increase in IQ in specific areas of the test, that is, in the areas of classification and analogies (being able to use logic on abstractions) (Flynn, 2013).  Flynn explains that this is likely representative of the change in thinking patterns of humans over time, especially when it comes to the hypothetical (Flynn, 2013).

There are a variety of explanations for the Flynn Effect. James Flynn himself describes some of these possible explanations in his Ted Talk (Flynn, 2013).


First, he discusses education as an explanation, describing how “the tenor of education has changed.  We are educating people to take the hypothetical seriously, to use abstractions, and to link them logically” (Flynn, 2013). This development in education likely explains the observed increase in IQ specifically on analogies and being able to apply logic to abstract ideas (Flynn, 2013).

In addition to higher quality education being available in modern times, more people have access to education now than in the past, which may also contribute to the effect.

Access to information

We are in an age of information and can research almost any topic through the internet. It is much quicker and easier to digest information than it would have been in past decades. Thus, with more access to information, it makes sense to believe our intelligence can increase.

Exposure to complex tasks

Overtime, our world has become more and more complex, with new inventions and developments occurring all around us. These new aspects of our world are often much more advanced and require a developed mind to engage with and to understand them.

For example, the relatively new emergence of video and computer games has led to humans developing skills in these cognitively demanding tasks. Therefore, exposure to new, more advanced tasks may be another explanation for the Flynn Effect.

Health and nutrition

Finally, it is thought that improvements in health and nutrition may both help to explain the Flynn Effect.

Over the past century, there has been a better awareness of health, such as there being a decrease in the amount of people who smoke and the discontinuation of the use of harmful lead paint. There have also been improvements in the prevention and treatment in infectious diseases and improvements in nutrition.

Having healthier people can mean that more individuals can reach their full potential and become more intelligent.

Why is the Flynn Effect Important?

The Flynn Effect is important because it highlights the development of human intelligence over time. Although it may be obvious in certain areas that human civilization has become more intelligent with time, the Flynn Effect provides a concrete representation of this increase.

Using IQ tests to look at changes in human intelligence over time provides a tangible representation of intelligence that can be compared and contrasted.

Additionally, the Flynn Effect suggests that modern education works and is effective. The Flynn Effect may therefore encourage more modern teaching approaches. If IQ tests are an accurate representation of human intelligence, then an increase in the average human IQ score over time would suggest an increase in intelligence.

Intelligence can be developed and increased with education, so this would therefore suggest that recent education methods may be more effective than past methods.

Finally, another reason that the Flynn Effect is so important is because of the role of IQ in intellectual disabilities, especially “in high stakes decisions when an IQ cut point is used as a necessary part of the decision-making process”, such as in “the determination of intellectual disability in capital punishment cases” (Trahan et al., 2014).

Additionally, IQ plays a role in “determining eligibility for special education and American Disability Act services and Social Security Disability Insurance (SSDI) in the United States” (Trahan et al., 2014).

These are just a few examples of how important IQ can be in determining the course of some people’s lives. This emphasizes the importance of research on human IQ and how it may change over time.

Is the Flynn Effect Valid?

Supporting Evidence

The 2014 meta-analysis of the Flynn Effect, as mentioned above, perhaps provides the most support for the Flynn Effect, due to the size of the study (Trahan et al., 2014).  This study found that “across 285 studies (N = 14,031) since 1952 with administrations of 2 intelligence tests with different normative bases, the meta-analytic mean was 2.31…standard score points per decade” (Trahan et al., 2014).

This meta-analysis provides support for the Flynn Effect on a wide scale, given the large amount of studies that it used in its analysis (Trahan et al., 2014).

In addition to James Flynn’s original study of the Flynn Effect, he also conducted a study in 1987 where he found that “data from 14 nations reveal IQ gains ranging from 5 to 25 points in a single generation” (Flynn, 1987, as cited in Rodgers, 1998). These findings provide additional support for the Flynn Effect in a variety of places around the world (Flynn, 1987, as cited in Rodgers, 1998; (Flynn, 2009, as cited in Trahan et al., 2014).


Conversely, there are a variety of studies and reviews that critique the Flynn Effect.

One such review by Rodgers (1998)  argues that “the acceptance of the effect has been too quick” and that “before the effect is taken seriously by the community of social science researchers, its very existence should not be questionable” (Rodgers, 1998).

Furthermore, Rodgers argues that “research addressing the legitimacy and meaning of the effect should precede research testing for and evaluating causes of the effect” (Rodgers, 1998).

Because there are opposing views on the existence of the Flynn Effect and other aspects of the effect, research should focus on finding a more solid foundation of the effect before exploring other interactions of the effect (Rodgers, 1998).

Overall, more data on IQ tests from more participants from a variety of places around the world will be beneficial towards achieving this goal.

Is the Flynn Effect Reversing?

Some researchers have found evidence for a “negative Flynn Effect”, that is, that the Flynn Effect has actually begun to reverse (Dutton et al., 2016, as cited in Bratsberg & Rogeberg, 2018; Pietschnig & Voracek, 2015, as cited in Bratsberg & Rogeberg, 2018)

Numerous studies on the Flynn Effect in a variety of countries have provided support for this “negative Flynn Effect” (Dutton et al., 2016, as cited in Bratsberg & Rogeberg, 2018). However, a 2014 meta-analysis of the Flynn Effect did not find support for the Flynn Effect reversing (Trahan et al., 2014).

There seems to be support for both arguments, which emphasizes the need for further research on the Flynn Effect in order to determine what is the true pattern of human IQ over the course of history.


What is an example of the Flynn Effect?

An example of the Flynn Effect is in intelligence scores. It is thought that if a person took an IQ test in the 19th Century, the average score would be significantly lower than it would be if that same person took an IQ test today.

This is because the average human IQ is believed to have increased over time, and therefore someone would naturally perform better on an IQ test nowadays than the same person would perform on an IQ test decades ago.

How does the Flynn effect relate to education?

The Flynn Effect relates to education because education is often thought of as relating to IQ levels. It is a common thought that a human that has been able to access education would have a higher IQ than a human who has not been able to access education.

Additionally, someone who has been able to receive a higher level of education than someone else would likely be expected to have a higher IQ. And, as James Flynn explained in his Ted Talk, education is a key possible explanation for the Flynn Effect (Flynn, 2013).

Are jobs more cognitively demanding than they were in the past?

As James Flynn discussed in his Ted Talk, jobs have become more cognitively demanding over time (Flynn, 2013).

This development has both contributed to the increasing complexity of the world around us, and has also been a result of this increase. More people with more cognitively demanding jobs has led to the development of many advanced aspects of our world today, including new technologies and inventions.

Furthermore, these new technologies and inventions have led to the creation of more cognitively demanding jobs, as they require more people to be able to work with and further develop these new advances in our society.

Are IQ tests reliable?

It is important to consider the reliability of IQ tests and how well, if at all, they truly represent the intelligence of human beings.
James Flynn discusses the reliability of IQ tests in his 1987 paper titled “Massive IQ gains in 14 nations: What IQ tests really measure” (Flynn, 1987).

In this paper, Flynn looked at increases in IQ in 14 nations and concluded that “IQ tests do not measure intelligence but rather a correlate with a weak causal link to intelligence” (Flynn, 1987).

It is also questionable whether IQ tests can be used to measure intelligence in a variety of cultures. IQ tests are argued to be culturally biased since they are often designed for and favor white, middle class groups and may not be applicable to other groups (Ford, 2004).

It is important to consider what IQ tests really measure when attributing the measurement of human intelligence to these tests, so that we can draw accurate conclusions about human intelligence overall.


Bratsberg, B., & Rogeberg, O. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences, 115 (26), 6674-6678.

Dutton, E., van der Linden, D., & Lynn, R. (2016). The negative Flynn Effect: A systematic literature review. Intelligence, 59, 163-169.

Flynn, J. R. (1984). The mean IQ of Americans: Massive gains 1932 to 1978. Psychological bulletin, 95 (1).

Flynn, J. R. (1987). Massive IQ gains in 14 nations: What IQ tests really measure. Psychological bulletin, 101 (2), 171.

Flynn, J. R. (2007).  What is intelligence?: Beyond the Flynn effect . Cambridge University Press.

Flynn, J. R. (2009). The WAIS-III and WAIS-IV: Daubert motions favor the certainly false over the approximately true. Applied Neuropsychology, 16 (2), 98-104.

Flynn, J. (2013). Why our IQ levels are higher than our grandparents” | James Flynn. Ted Talk

Ford, D. Y. (2004). Intelligence testing and cultural diversity: Concerns, cautions, and considerations. National Research Center on the Gifted and Talented.

Herrnstein, R. J., & Murray, C. (2010). The bell curve: Intelligence and class structure in American life . Simon and Schuster.

Lynn, R. (2009). What has caused the Flynn effect? Secular increases in the Development Quotients of infants.  Intelligence 37 (1), 16-24.

Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains: A formal meta-analysis of the Flynn effect (1909–2013). Perspectives on Psychological Science, 10 (3), 282-306.

Rodgers, J. L. (1998). A critique of the Flynn effect: Massive IQ gains, methodological artifacts, or both?. Intelligence, 26 (4), 337-356.

Teasdale, T. W., & Owen, D. R. (2008). Secular declines in cognitive test scores: A reversal of the Flynn Effect.  Intelligence 36 (2), 121-126.

Trahan, L. H., Stuebing, K. K., Fletcher, J. M., & Hiscock, M. (2014). The Flynn effect: a meta-analysis Psychological bulletin, 140 (5), 1332.

Williams, R. L. (2013). Overview of the Flynn effect. Intelligence, 41(6), 753-764.

Saul Mcleod, PhD

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Educator, Researcher

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.

Eleanor Myers

Research Assistant at Princeton University

Psychology Undergraduate, Princeton University

Eleanor Myers is a senior psychology major at Princeton University.  She studies language development as a research assistant in the Princeton Baby Lab.