Want a daily email of lesson plans that span all subjects and age groups?
Learn more

The dark history of IQ tests - Stefan C. Dombrowski

  • 808,418 Views
  • 10,194 Questions Answered
  • TEDEd Animation

Let’s Begin…

In 1905, psychologists Alfred Binet and Théodore Simon designed a test for children who were struggling in school in France. Designed to determine which children required individualized attention, their method formed the basis of the modern IQ test. So how do IQ tests work, and are they a true reflection of intelligence? Stefan C. Dombrowski explores how the tests have been used throughout history.

Create and share a new lesson based on this one.

About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Stefan C. Dombrowski
  • Director Serin İnan
  • Narrator Addison Anderson
  • Storyboard Artist Ali Anılır
  • Animator Gürkan Gürler
  • Compositor Gürkan Gürler
  • Sound Designer Deniz Doğançay
  • Music Deniz Doğançay
  • Director of Production Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Producer Bethany Cutmore-Scott
  • Associate Editorial Producer Elizabeth Cox
  • Script Editor Alex Gendler
  • Fact-checker Eden Girma
  • See more
Additional Resources for you to Explore
IQ tests have been used to better understand individual differences in intelligence and promote human well-being. They have also contributed to human misery through improper interpretive practices. How have IQ tests been interpreted over the past century and how should they be used to best promote human well-being?

Binet and Simon largely created their intelligence test (IQ test) to determine which children required more individualized attention. IQ test results have since been interpreted in an anti-scientific fashion. It is not that the IQ tests are problematic. They are not, and provide important information. It is that scientists and policy makers have overextended IQ test’s interpretive capabilities. Early research on IQ tests indicates they were used to justify US-based sterilization policy and Nazi Germany extermination practices. In the United States early large scale IQ test research was also used to make characterizations about entire races even though the research did not properly account for test score differences related to education, English language exposure, and socioeconomic status. IQ tests have been similarly used to make psychiatric decisions regarding whether an individual should receive a diagnosis such as depression or mania.

Today, some continue to use IQ tests beyond the scope of their scientific capabilities. Cognitive profile analysis, a practice that has been criticized in the scientific literature as being no more accurate than a coin flip, is used by some psychologists to determine whether a child experiences a learning disability. This practice entails looking for a pattern of cognitive strengths and weaknesses through investigation of an IQ test’s subtest or index level dispersion of scores.

Why do psychologists continue to use IQ test cognitive profile analysis in this manner? There is an abundance of commercial literature that promotes these practices within the test manuals of many major IQ tests. Additionally, books, chapters, and presentations on cognitive profile analytic practice, often written by those who often have a conflict of interest, are widely commercially available and endorse this practice for diagnosing learning disabilities and understanding learning deficiencies.

Even though cognitive profile analytic practices remain popular, it turns out that over 70 years of IQ test cognitive profile analytic research has not supported this practice. Instead, cognitive profile analysis has been rebuked by most of the scientific corpus. Yet, because of the co-existence of these contrasting bodies of literature, psychologists and the lay community are left to discern which literature base has greater scientific merit: books, chapters, and presentations published by many with a financial conflict of interest or empirically-based research studies that have been vetted during the peer reviewed process.

There is little doubt that IQ tests have improved human well-being by assisting in proper educational and social services programming for individuals with extreme scores. However, when IQ tests are promoted, and subsequently used, in a way opposed to scientific evidence then this serves to perpetuate a practice that could, at best, be harmless or, at worst, contribute to adverse diagnostic and policy decisions.

So, what does the preponderance of the research say about how to properly interpret IQ tests results? Here we come back to the future and return to Binet and Simon’s original inclination. We should place primary emphasis on the global IQ test score (full scale IQ test score) and only nominal, if any, consideration should be given to index level composite scores such as working memory, verbal comprehension, visual-spatial functioning, and processing speed. Why do I say only cautionary emphasis? Because the statistical contribution of these subscale composites is often so low that interpretation of them does little to contribute to an understanding of an individual’s cognitive capacity other than make us feel like we have garnered additional insight, which often is not the case. The preponderance of the empirical evidence does not support the interpretation of an IQ test’s subtests, nor the use of either IQ test subtests or index level composites for purposes of learning disabilities classification or any other psychiatric classification other than intellectual disability.

Of course, we don’t want to throw the baby out with the bath water. There is significant merit to the use of IQ tests. They are necessary for the classification of intellectual disability. They are also useful to gain a sense of an individual’s trajectory for learning and vocational success. For instance, an individual who scores at the 90th percentile on an IQ test’s full scale composite will likely perform better academically and vocationally than an individual who scores at the 10th percentile. Please keep in mind, however, that IQ test results are probabilistic, not deterministic.


It is time for the field of psychology, and policy makers, to regard the preponderance of the scientific research and interpret IQ tests in an evidence-based manner. Will evidence-based IQ test interpretive practice and policy catch on anytime soon? History suggests that it will not. More than 70 years of IQ test cognitive profile analytic research has not found a typology of cognitive score combinations that is useful for diagnosis. Still, many continue to hold out hope and devise new profile analytic methods in search of elusive clinical gold.

Perhaps this video and subsequent discussion will slowly engender a change in thinking about how to properly interpret IQ tests, and move psychology and society more broadly toward a scientifically guided approach?


Customize This Lesson

Create and share a new lesson based on this one.

About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Stefan C. Dombrowski
  • Director Serin İnan
  • Narrator Addison Anderson
  • Storyboard Artist Ali Anılır
  • Animator Gürkan Gürler
  • Compositor Gürkan Gürler
  • Sound Designer Deniz Doğançay
  • Music Deniz Doğançay
  • Director of Production Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Producer Bethany Cutmore-Scott
  • Associate Editorial Producer Elizabeth Cox
  • Script Editor Alex Gendler
  • Fact-checker Eden Girma
  • See more