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Decline in Intelligence?

June 14, 2013

They say that necessity is the mother of invention. We live today in a time of relative plenty. Not only is there a chicken in every pot, there's also a cellphone in every purse. Unlike all humans before the present era, most of us don't really need to think that hard about how to get our next meal, and we've established government programs and charitable organizations to help those who do.

At the time when inexpensive calculators were just reaching consumers, math teachers bemoaned the idea that students wouldn't learn hand calculation when they had access to calculators. At the same time, I read a science fiction short story based on that idea. In a future age of the military-industrial complex, when all munitions were computerized, no one was skilled in hand calculation.

As any cryptographer knows, when something is algorithmic, it's predictable, so no country's computerized missiles were any better than the others. One general had the idea that he could make his missiles less predictable by adding a human element. His solution was to have these manned by servicemen doing long division with paper and pencil.

Lest you think the use of biology to control missiles is too fantastic, Project Pigeon was a World War II project that utilized pecking pigeons as missile guidance. Pigeons were trained to peck at a target image, and the location of the pecks steered the missile. This project, which originated with B.F. Skinner, continued from 1948-1953 as Project Orcon; but it was terminated when electronic control was proved reliable.

Intelligence is an admired human trait. My maternal grandmother, who was born in 1895, would tell me stories about how smart her father was. He was a farmer, and farmers need to repair their equipment. They often invent things to make the equipment work better. From what she said, he also invented the hair comb, but I suspect that he just enjoyed carving wooden combs for his daughters.

It's apparent to all that the degree of intelligence, however that might be defined, differs between people. Psychologists decided they could measure intelligence, so intelligence testing has been a part of human culture since the second decade of the twentieth century.

Lewis Terman, a psychologist and the father of the notable electrical engineer, Frederick Terman, invented the Stanford-Binet IQ test in 1916 to quantify intelligence. I wrote about the Termans and intelligence testing in two previous articles (Frederick Terman, July 12, 2011 and Extreme Intelligence, October 14, 2011).

The Stanford-Binet test gave us the notion of IQ, or Intelligence Quotient, The quotient label comes from its definition of intelligence as the ratio of "mental age" to "physical age," since a precocious child will function mentally as well as someone several years his senior. Statistics have allowed a better definition than this quotient (see figure).

The IQ bell curve.

Idealized Distribution of IQ Scores.

The mean is 100, and the standard deviation is 15.
It can be seen from the curve that IQ scores below 60 and above 140 are very rare.

(Graph by Alessio Damato, via Wikimedia Commons))

One long-standing question about intelligence is the nature vs. nurture debate about whether general intelligence is mostly genetic or a function of a person's environment. It appears that the heritability accounts for about three quarters of a person's intelligence when he reaches adulthood.

Scientists are often inspired by the acknowledged geniuses in their cohort. Catharine Cox Miles published a historiometric study in 1926 in which she estimated the IQ of some prominent scientists.[1] I've tabulated her estimates for some physicists,[2] some others I found,[3], and the documented IQ values for two twentieth century scientists.[4] I've included Linus Pauling as a physicist, although he's often mistaken for a chemist.[5]

PersonEstimated IQRef.
Leonardo da Vinci220[2]
Isaac Newton190[2]
Galileo Galilei185[3]
Johannes Kepler175[2]
Linus Pauling170[3]
Albert Einstein160[2]
Stephen Hawking160[2]
William Shockley129[4]
Richard Feynman126[4]

Linus Pauling in 1954

Nobel Prize in Polymath?

Linus Pauling won the 1954 Nobel Prize in Chemistry and the 1962 Nobel Peace Prize, but he came close to the double helix model of DNA, and he did as much quantum mechanics as most physicists. Pauling is an example that the boundaries between disciplines are arbitrary.

(US Library of Congress photograph no. LC-USZ62-76925, via Wikimedia Commons, modified for artistic effect.)

One trend noted is the apparent increase in intelligence since the earliest days of massive testing to the present day, the so-called Flynn effect. This is too short a time period for any genetic selection, so people have looked for other explanations, such as better public education and a richer environment. As one who spent his childhood with a transistor radio and not a tablet computer, I can see how a richer environment could be important; but I also see how children use their tablets, and it's not for education.

IQ tests are not the only way to measure intelligence. You can use visual reaction time to measure how fast those mental circuits actually operate. Reaction times are highly correlated with the score from IQ tests and they're not culturally subjective, which IQ tests are often argued to be.

Psychologists from Umeå University, Sweden, Vrije Universiteit Brussel, Belgium, the University of Amsterdam, The Netherlands, and University College Cork, Ireland, have done an analysis of visual reaction time data going back to the Victorian era. They've concluded that general human intelligence has declined from the Victorian era. Their analysis is published in a recent issue of the journal, Intelligence.[6-9]

An apparatus called the Hipp chronoscope was invented around 1850, and it was used almost immediately by psychologists to take reaction time measurements to thousandths of a second accuracy. The research team used fourteen sets of such data ranging from 1884-2004. Reaction time is the time it takes a person to press a button after seeing a visual signal.[9]

In 1889, the average man had a reaction time of 183 milliseconds, and the average woman, 188 milliseconds.[7] Men in 2004 had an average reaction time of 253 milliseconds, and women, 261 milliseconds.[7] This is equivalent to a decreased IQ of 14 points, or nearly one standard deviation on the IQ bell curve, from 1889 to 2004.[6]

These data, as are most psychological data, have quite a bit of scatter, as figure one from the paper, nicely available for inspection without the hefty purchase price for the article, shows. The scatter means that the actual effect might be larger, still; or, smaller.[7] As was pointed out by one commentator, using the analogy of walking and chewing gum at the same time, reaction times from Victorian days, before our age of persistently short attention spans, might not be measuring the same thing.[8]

The study authors offer one hypothesis for this effect which won't score points for political correctness. They write that it might be a result of dysgenic fertility, which means essentially that smart people have fewer children than others.[6,8] Highly intelligent women are known to have fewer children than other women.[9] Over the course of time, a greater population of lower IQ people dominate.[8]

Let me interject my own hypothesis of what might be happening. Could it just be that modern people have much fatter, lazier fingers, so pressing buttons takes more time? Perhaps the coming "Generation-Z," with its practice on cellphone keypads, might bring the reaction time scores back into line.


  1. Catherine Morris Cox, "The Early Mental Traits Of Three Hundred Geniuses," Stanford University Press, 1926, 842 pages (via Google Books).
  2. Nicole Williams, "IQ Scores of Famous People Past and Present". This link is no longer available, since Google has discontinued its "knol" service.
  3. Estimated IQs of some of the Greatest Geniuses.
  4. Physics Forums Message Thread No. 178932.
  5. Such a comment, if posted on a chemistry forum, would definitely be considered "flamebait."
  6. Michael A. Woodley, Jan te Nijenhuis and Raegan Murphy, "Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time," Intelligence (In Press), May 7, 2013, DOI: 10.1016/j.intell.2013.04.006.
  7. Nick Mcdermott, "Were the Victorians cleverer than us?" Daily Mail, May 13, 2013.
  8. David DiSalvo, "Think Fast, Are We Really Getting Dumber?" Forbes, May 26, 2013.
  9. Macrina Cooper-White, "People Getting Dumber? Human Intelligence Has Declined Since Victorian Era, Research Suggests," The Huffington Post, May 22, 2013.

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