Why does humanity get smarter and smarter?

Intelligence tests have to be adjusted all the time because people score higher and higher. If the average human of today went 105 years back in time, s/he would score 130, be considered as gifted, and join clubs for highly intelligent people. How can that be?

IQ_increase_base_graphic_v.2_EnglishThe IQ growth

The picture above shows the development of humanity’s intelligence between 1909 and 2013. According to IQ-scores people got smarter and smarter. During the last 105 years, people’s scores increased by as much as 30 IQ-points. That is equivalent to the difference between intellectual disability and normal intelligence. Ever since the discovery of this effect by James Flynn, the underlying reason has been hotly debated. A new analysis combines all available studies into one overall picture in order to find answers.

Jakob Pietschnig and Martin Voracek included all available data pertaining to IQ increases from one generation to another: nearly 4 million test takers in 105 years. They found that IQ scores sometimes increased faster and sometimes more slowly. Check the difference between the 1920s and WWII in the figure above. Moreover, different aspects of intelligence change at different speeds. So-called crystallized intelligence (knowledge about facts) increased only at a rate of 0.2 points per year. So-called fluid intelligence (abstract problem solving), on the other hand, increased much faster at 0.4 points per year.

Five reasons for IQ growth

Five reasons appear to come together to explain this phenomenon:

1) better schooling: IQ growth is stronger in adults than in children, probably because adults stay longer and longer in school.

2) more experience with multiple choice tests: since the 1990s the multiple choice format has become common in schools and universities. Modern test takers are no longer put off by this way of asking questions in IQ tests and might resort to smart guessing.

3) less malnutrition: the slow IQ growth during the world wars might have something to do with a lack of nutrients and energy which the brain needs

4) better health care: the less sick you are, the more your brain can develop optimally

5) less lead poisoning: since the 1970s lead was phased out in paint and gasoline, removing an obstacle for healthy neural development

 Am I really smarter than my father?

According to the Flynn effect, my generation is 8 IQ-points smarter than that of my parents. But this only relates to performance on IQ tests. I somehow doubt that more practical, less abstract, areas show the same effect. Perhaps practical intelligence is just more difficult to measure. It is possible that we have not really become more intelligent thinkers but instead more abstract thinkers.

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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 : a journal of the Association for Psychological Science, 10 (3), 282-306 PMID: 25987509

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Figure: self made, based on data in Figure 1 in Pietschnig & Voracek (2015, p. 285)

One comment

  1. When it comes to explaining if humanity is getting smarter and smarter, we need to look through a lens that includes a full spectrum. Although humanity itself has advanced technologically beyond belief has the intelligence of the full populous followed? In hind sight, it depends. When looking at American culture and background we can see developments in many areas but deficiencies in others. Americans have the ability to build monuments and create new and improved things with machinery and electronics, but when it comes to using just what we have we can’t do it. All together we have traded one intelligence for another. With this being said, an IQ test does not change to get harder but instead changes to fit the knowledge todays people should contain.

    Now the 5 reasons of why IQ has grown is only a bit shaky. Sure we have better schooling, but only in certain regions of the world. Even if a very small part is deprived of grade A education they still count. So that reasoning depends on the region that is being tested. More experience with multiple choice tests is more solid than its predecessor. Today people have more experience with multiple choice tests making it easier to guess correctly. The one question I have formed for this though is, should we change the method in which we take tests in to truly test a persons cognitive ability? Thirdly, there is ‘less malnutrition.’ Again, this depends on the region of the world you sit. Even in the most wealthy of countries there is poverty. Children, adults, families starve every day. Such as in African countries, India, and even the United States. Next is our healthcare systems. Although healthcare has improved, its affordability has not. So health care depends on whether you can afford it or not as well as the availability of it. Some people would rather be sick than deal with the ridiculous prices of health care. And even if health insurance is available the prices are still too high for many people to afford. Healthcare is also not so readily available in all regions of the world. Some just have medicine men. Less lead poisoning may have something to do with rising IQs. Although it was removed from certain chemicals and appliances we use today, we still have exposure to other harmful toxins. They may do less damage but all the same are dangerous.

    So in conclusion the 5 reasonings given here are solely based on the regions being tested.

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