A new study suggests that people living today are considerably less intelligent than people living a couple centuries ago, to the tune of 14 fewer IQ points on average.
The metric evaluated to reach this conclusion isn't one most would guess. Rather than comprehensive IQ test scores declining over time, researchers focused on declining reaction times--a metric that correlates with general intelligence for reasons that aren't entirely clear.
In psychological parlance, the study of reaction times is called mental chronometry. If you participated in a mental chronometry study, you would be presented with a stimulus (let's say an intermittently flashing blue light on a monitor) and asked to react to the stimulus as quickly as possible (in this example by pushing a button when the blue light flashes). How quickly you react is thought to be a measure of your brain's processing speed.
General intelligence (also called the "g factor") is comprised of multiple parts, mental processing speed among them. And it's this speed that researchers analyzed using psychometric data from the Victorian era beginning in 1884, up through 2004, culled from 14 intelligence studies conducted during that span (the handy thing about reaction time is that it's testable with several different methods, and older methods are still considered valid). The results aren't flattering to us moderns: IQ, as measured by reaction time, dropped 1.23 points per decade, for a total of 14 points in the hole.
Before I throw a little devilish advocacy at this troubling conclusion, it's first worth asking what could possibly be the cause of declining intelligence if the finding is accurate? Researchers who conducted this study believe the drop is related to "dysgenic fertility" -- murky jargon for the theory that smarter people have fewer kids.
The theory goes something like this: smart people are more creative and industrious than the masses, and their energy—consumed by productive pursuits—is less available for bringing children into the world. Kids are, after all, energy and time intensive, and the richest brains don’t have the energy or time to raise a brood. As the years pass, this proclivity for productivity results in the genetic selection of less intelligent people emerging on the scene generation after generation.
Whether or not that argument is airtight is a topic for another day; suffice to say for now that it has many supporters who believe it’s the tidiest way to account for a snowballing decline in general intelligence. And it’s also what makes the Victorian era, noted for its geyser of prodigious innovation, such a strong starting point for this research.
Having said that, let’s now toss a couple wrenches into the works.
First, the study results run counter to a well-studied phenomenon known as the “Flynn effect.” Named after James Flynn, a political scientist who first discovered it in the mid-1980s, the Flynn effect is the surprising trend of increasing intelligence over time.
Flynn found that IQ increases about 3 points every 10 years, based on results of well-established tests of intelligence including the Wechsler Intelligence Scale for Children and its adult counterpart. That’s nearly a 10-point increase per generation. Rather than accounting for one aspect of intelligence, like processing speed measured by reaction time, the Flynn effect considers a range of factors cutting-across verbal and mathematical aptitudes—and in general it evidences a clear advantage for the modern mind.
The reasons for the Flynn effect are likely many, but the biggest one is that ever since the industrial revolution we’ve been the beneficiaries of more education, more technology, and more opportunities for sharpening our minds than our pre-industrial ancestors. In other words, the Flynn effect shows undeniably strong societal and cultural influences on intelligence.
The takeaway from the Flynn effect is not that our forebearers were stupid, but rather that as time passes we'd do well to recalibrate what “general intelligence” really means. Comparing your intelligence with that of someone living half a century before the industrial revolution isn’t apples-to-apples; at best, it’s a comparison of apples grown in radically different soils and climates.
The second wrench to fling (not nearly as significant as the Flynn effect) is that reaction time appears to be changeable. Research suggests that it may in fact be changeable by doing something as simple as chewing gum.
If reaction time is so easily altered, we might ask if it’s such a sturdy indicator of general intelligence after all. At the very least, we might ask if sweeping arguments about the advancing dumbnification of the Western world should be built on something that gnawing a few sticks of Big Red can tweak.
At any rate, it would seem that rumors of our stupidity have been somewhat exaggerated. We may or may not be significantly smarter than those who came before, but the evidence isn’t pointing to us being alarmingly denser. It's even possible, if not probable, that we’re right where we should be.