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11:48in productionCh. 1 · A century-long climb/ 11:48 · ceiling 15 min
Neuroscience · Evolution

Flynn effect

1987

IQ scores rose steadily for a century — but that doesn’t mean we got smarter.

The Flynn effect documents a robust, linear, global rise in IQ test scores over the 20th century — especially on fluid and crystallized intelligence measures — identified by comparing newer generations’ scores on older tests. It is real, measurable, and widespread. But it says nothing about whether humans became more intelligent in any meaningful sense — only that they got better at this particular kind of test.

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Chapters & takeaways4
  1. 1:04
    A century-long climb

    IQ scores rose continuously and linearly across the 20th century — not in spurts, not just in labs, but globally.

  2. 2:58
    How the rise was measured

    The effect was found by giving old tests to new people — and seeing scores soar above 100 across every test, age, ability level, and industrialized nation.

  3. 4:50
    Numbers you can trust

    British children gained 14 points on Raven’s; US scores rose 3 points per decade on Wechsler — concrete, comparable, documented.

  4. 6:59
    Who named what — and who saw it first

    It’s named after James Flynn, but Herrnstein and Murray coined the term — and Tuddenham saw it first in 1948.

Worth your time?

Yes. Study the whole thing.

4.5/ 5
What works
  • exposes limits of IQ as a stable metric
  • forces scrutiny of test design and cultural bias
  • reveals how deeply environment shapes measured cognition
What does not
  • proves intelligence increased
  • applies equally to non-industrialized nations
  • continues unchanged today
  • measures general cognitive capacity
Study it if
  • educators
  • psychologists
  • policy makers assessing cognitive trends
Skip it if
  • anyone seeking proof of rising human genius
The written brief1 min read

What the work claims

The Flynn effect claims a sustained, measurable increase in IQ test scores — especially fluid and crystallized intelligence — over the 20th century and into the 21st, observed globally and across all tested demographics.

How it was done

Researchers compared scores of newer standardization samples on older IQ tests. Each time a test is revised, it is restandardized to set the new sample’s average to 100. When those newer samples took older versions of the same tests, their average scores were consistently above 100.

What holds up

The rise is real, global, long-term, and linear across industrialized nations. It appears on every major IQ test, every age group, every ability level, and every modern industrialized country. British children gained 14 points on Raven’s Progressive Matrices from 1942 to 2008. US Wechsler scores rose ~3 points per decade.

What does not

It does not establish that general intelligence increased. It does not prove gains reflect improved reasoning, problem-solving, or real-world competence. It does not show the trend continues uniformly everywhere today.

Why it matters beyond the lab

It undermines assumptions that IQ is fixed or biologically anchored. It shows test performance responds powerfully to environmental change — education, technology, visual culture, test familiarity — without confirming what cognitive capacity those changes represent.

Is it worth your time

Yes — it forces a confrontation with what IQ tests actually measure, and exposes a persistent gap between statistical trends and claims about human intelligence.

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