The decline of Human Intelligence: Why Are People Stupid?


This was inspired by some of the questions here. This isn't to hurt anyone, just wanted to look into this. Most people on this website are probably decently smart, but you can be the judge of that. IMPORTANT: Added the Bold to help, this is a long MyTake so I hope that makes it easier to read in bites.

The decline of Human Intelligence: Why Are People Stupid?

Humanity has experienced high levels of intelligence and numerous technological advances since the 18th century, however IQs are in the decline and falling rapidly. In a study first published by National Academy of Sciences showed that IQ scores has fallen every year by 0.3 points since the mid-1970s. Western countries has lost a total of 15 IQ points since the peak in the 19th century, which is as significant difference.

Things genetically correlated with higher intelligence has dwindled, from your reaction speed and the complexity of your vocabulary. Your academic success in school and socioeconomic status ate also related to your intelligence.

In countries like Iceland, the genetic disposition of educational attainment is being selected out of the population. In a research article published on PNAS noted "A recent study of ∼20,000 genotyped Americans born between 1931 and 1953 provided direct evidence that the genetic propensity for educational attainment is associated with reduced fertility-". People who are highly educated have fewer children and fewer generations.

The decline of Human Intelligence: Why Are People Stupid?

The effect is more pronounced for women as those of higher socioeconomic status usually use birth control more effectively and limit their fertility. Women of higher IQs also tend to seek abortions on time when faced with an unwanted pregnancy (check the last source on the list).

yet, what is intelligence? How is it measured? There are different kinds of intelligence, like your abilities and skills. How well you do socially and communicate is correlated with intelligence (0.3 correlation, 1.0 is the highest, 0.1 means basically not correlated). What is underpinning the different types of intelligence and your overall cognitive ability is the G-factor, otherwise known as general intelligence. General Intelligence is highly genetic at 0.8 heritability with a few rare outliers. it is difficult to measure, IQ tests can only indirectly measure it. Concisely, Intelligence can be defined as "the ability to solve cognitive problems and to solve them quickly."

There isn't currently any based way to change your IQ although you can improve at doing tests. The average IQ score in developed countries is more or less 100, this would include careers like data entry, becoming a Clerk, Cashier, or Police Patrol Officer. Someone around an IQ score of 87-93 would likely work as a Janitor, Factory worker, or packager. "What IQ predicts to some degree is how rapidly you can learn something but once you've learned it, it doesn't necessarily predict how well you do at it. People with lower IQs are more suitable to more repetitive jobs."

The decline of Human Intelligence: Why Are People Stupid?

On the other hand, a portion of the population has an IQ of 85 or lower. The exact number varies. The average IQ in the US is 98 so it's likely that 19% of Americans have an IQ of 85 or less. Jobs for people with an IQ of 85 or less are limited, even the military bans people with an IQ of less than 83 from enlisting. People with an IQ lower than 95 can experience difficulty finding work. Those chronically on welfare (In the US) have an average IQ of 90, according to an article published on PBS. Criminals often have an IQ lower than 95.

However, a person with a below-average intelligence can still live a decent life if they do choose to, personality also plays a big role in this. One of the things that Richard Haier mentioned was that although most people would choose to be smarter, intelligence doesn't determine your character exactly.

Why is Intelligence decreasing though? This is the question I wanted to answer with this post, hopefully with an understanding of it matters. Prior to the industrial revolution, Intelligence was being selected for, among other traits. Things like height, brain size, and facial symmetry are correlated to some degree with intelligence. Less intelligent people have more children and more generations. People with an average IQ or higher tend to have less than 2 children and have them later in life. Countries with a welfare state also help families of lower IQ to pass their genes on as previously mentioned. This as well as a lower child mortality rates means that natural selection weaken; traits that would have been selected against remain. The more intelligent a person is, the more likely they are to adopt to the current society and ideology. Religiosity is associated with having more children but the more intelligent a society is the less Religious it becomes. This is a factor that has affect many developed countries in Europe and North America as society has moved towards a more leftist, atheist norm.

Note: I might write about how does a Low IQ society and how the transition to one looks like. Developed countries appear to be in the middle of a transition. Demographics is a topic I've found interesting for a while now. I hope this works as an introduction of sorts for the both of us.


I've been looking into this topic for a while but this is a few articles and videos that I used specifically for this MyTake, feel free to take a look:

  • Why are our IQs Falling? (Video by TDLR News Global)
  • Lecture by Edward Dutton at ASBIRO University on the decline of intelligence
  • (Video by Hydrostatus Systems)
  • Richard Haier: IQ Tests, Human Intelligence, and Group Differences | Lex Fridman Podcast #302 (Video by Lex Fridman )
  • IQ Test Scores Are Getting Higher, But Are Humans Actually Getting Smarter? (Article by Sciencealert)
  • Genetic and environmental influences on reaction times: Evidence from behavior-genetic research (Study published on research gate)
  • Selection against variants in the genome associated with educational attainment (Article on , first on PNAS)
  • How much is academic achievement shaped by genes? (Article published on the BBC)
  • The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence (Article published on PNAs)
  • Jordan Peterson - What Kind Of Job Fits Your IQ (There's an animated clip posted by The Wisdom Wire on Youtube)
  • Research Confirms a Link between Intelligence and Life Expectancy (An article published on the Scientific American).
  • Analysis: How poverty can drive down intelligence (Article published on PBS)
The decline of Human Intelligence: Why Are People Stupid?
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