According to overenthusiastic hacks at Wired, scientists have recently developed a way to scan your brain to predict just how intelligent someone is or how good you’ll be at certain tasks. This sounds like the beginning of a dystopian nightmare, rather than an actual field of research, that will end up with mandatory brain scans for everyone to “facilitate an appropriate job function” in some dark, gray lab in front of medical paper pushers, true. But it only sounds like this because the writer is more interested in page views than the actual study, which really has nothing to do with one’s intelligence but actually tested whether you could identify someone by scanning how this person’s brain is wired. Rather than trying to develop IQ tests in a box, the researchers put the theory that your brain wiring is so unique that getting a map of it could identify you every bit as well as a fingerprint, to the test. Not surprisingly, they found that a high quality fMRI scan of your brain at work performing some standard tests can definitely be used to identify you.
All right, that’s all fine and well, after all, the fMRI scan is basically giving you insight into unique personalities, and no two people’s brains will work the same way. But where exactly would this whole thing about measuring intelligence come into play? Well, the concept of fluid intelligence, mentioned only three times in the study, was brought up as an additional avenue of research in light of the findings and revolves around the idea that certain parts of the brain having a strong connection will make you notably better at making inferences to solve new problems. Unlike its counterpart, crystallized intelligence (called Gc in neuroscience), fluid intelligence (or Gf) is not what you know, but how well you see patterns and come up with ideas. Most IQ tests today are heavily focused on Gf because it’s seen as a better measure of intelligence and the elaboration on what exactly the fingerprinting study had to do with predicting Gf was an extended citation of a study from 2012 which found a link between the lateral prefrontal cortex’s wiring to the rest of the brain and performance standardized on tests designed to measure Gf in 94 people.
Here’s the catch though. Even though how well your lateral prefrontal cortex talks to the rest of your brain does account for some differences in intelligence, much like your brain size, it really only explains 5% of these differences. Current theory holds that because your prefrontal cortex functions as your command and control center, what Freud described as the ego, a strong link between it and several other important parts of the brain will keep you on task and allow you to problem-solve more efficiently. Like a general commanding his troops, it makes sure that every other relevant part of your mind is fully engaged with the mission. But even if that theory is right and your preforntal cortex is well wired in a larger than median brain, close to 90% of what you would score on an IQ test can come down to level of education and other factors that generally make household income and education a better predictor of IQ scores than biology. Although in many ways it’s not that accurate either because style of learning and culture also play a role. All we can conclude is that the interplay between Gf, Gc, and education is very complex.
We should also take note of one study of popular theories of biological contributors to Gf which spanned 44,600 people and found no evidence that a combination of fMRI maps has predictive power when it comes to IQ points. In other words, we have a lot of ideas that seem plausible as to the biological origins of intelligence, but because our brains are very plastic, we are not all on a level playing field when it comes to the amount and quality of education we receive, and even our longest-running efforts for accurate Gc assessments have shown that we’re really bad at it, studies that claim predictive powers when it comes to our IQs using brain scans of 100 college students or fewer are extremely likely overselling their results. Not only that, but even when the studies do actively oversell, they still claim to explain only a tiny fraction of the score differences because they recognize how small and homogeneous their data sets really are. Not only do we not have an fMRI based tests for intelligence, we’re not even sure it’s possible. But those facts bring in far, far fewer page views than invoking kafkaesque sci-fi lore in a pop sci post…