Imagine that you live in the world of Harry Potter. One morning, while reading the Daily Prophet, you notice an intriguing news headline: “Biology of Magic Discovered!” According to the article, a team of researchers in the Ministry of Magic has identified a collection of neurons that are the basis for magical ability.
To accomplish this task, the researchers invited a dozen volunteer wizards and witches into the lab to perform magical feats while having their brains scanned. Sure enough, one region of the volunteers’ brains, known as the mid cingulate vortex, increased in activity during spellcasting. This observation led the team to conclude that this region is the distinct home of magic in the brain.
In real life, similar brain studies often garner media attention. This week, an op-ed in the New York Times, “The Point of Hate” by psychiatrist Anna Fels, asserted that a specific brain circuit is the location of hate, based on the findings of a neuroscience study from 2008. “Clearly,” writes Dr. Fels, “evolution has preserved hate as a powerful motivating force.”
But have scientists actually found a brain circuit for hate? Before I reveal the answer to that question (which, by the way, is “no”), let’s think about how to prove that a particular collection of neurons has a distinct psychological purpose, whether it’s hate or magic. That requires five steps that are well-known and accepted in scientific and wizarding circles.
Step 1 is to gather data. This is exactly what researchers in the Ministry of Magic did for their experiment: round up volunteers, have them cast spells, and record the brain data.
Step 2 is to show that the experimental results aren’t due to coincidence. Neurons fire all the time, after all, so maybe the brain activity observed by the Ministry researchers occurred by chance. So, an experiment must include many, many observations. It also needs to control extraneous factors that can introduce random error, such as whether the volunteers’ wands are in working order, or whether they drank too much butterbeer the night before. If the hypothesis still holds up (after some mathematical analysis), then the experiment has achieved a milestone called statistical significance, which means that the results are, in all likelihood, not due to chance.
Step 3 is to show that the claimed brain activity during spellcasting is consistently the same, no matter who does it or how it’s accomplished. This is called reliability. A single experiment with a dozen magic users is probably not reliable, because it might not be representative of the entire wizarding world. One must run multiple experiments with diverse groups of volunteers — say, purebloods and halfbloods of all ages and experience levels from all the wizarding schools. They should also cast a wide range of spells, to show that the effect is not limited to a handful of conjurings.
Step 4 is to show that the brain activity seen during acts of magic is specific to magic, i.e., different from that of other tasks. This is called specificity. If activity in the mid cingulate vortex increases not just during spellcasting, but also during anger, daydreaming, and bathing, then one cannot claim that the region is neurally specific to magic.
Step 5 is to rule out alternative explanations. Even if the mid cingulate vortex increased its activity during magical acts in a statistically significant, reliable, and specific way, could there be another reason for this activity? Maybe the spellcasters tested were from the same small town and had genetic similarities that accounted for the related brain activity. Or maybe magic also requires other parts of the brain that the scanning equipment wasn’t precise enough to record. Scientists must show that no other explanations are likely to account for their data.
In the end, if the experimental results are statistically significant, reliable, specific, and not explainable by other means — that is, the hypothesis has been put at risk and survived again and again — then, and only then, can one claim to have found the unique biological marker for magic or anything else. Results that are merely consistent with a hypothesis are a reasonable start, but they aren’t sufficient to make strong, causal claims like “We’ve found the circuit for magic.”
Which brings us back to the discovery of the alleged hate circuit. That study satisfied steps 1 and 2 by gathering data and showing that certain brain circuitry increased in activation in a statistically significant way. The study did not show reliability (step 3), however, since it included just a single sample of 17 test subjects.
The hate study also did not show specificity or rule out alternative explanations (steps 4 and 5). You see, some of the regions in the claimed “hate circuit” are well-known hot spots in the brain. They show an increase in activity in almost 6,000 other experiments on a wide variety of phenomena, such as memory, pain, hormone regulation, self-evaluation, mind wandering, and all sorts of emotions. No hot spot is tied to a single psychological function. The upshot is that the study does not provide sufficient evidence for a hate circuit, though the research paper is routinely cited for discovering one.
Finally, even if the hate study had satisfied all of steps 1–5, it likely suffers from a common flaw. Most brain-scanning studies perform only enough scanning to show the strongest, most robust activity in the brain, such as the hot spots in the hate study. Such studies, which scientists call “underpowered,” produce brain scans that look like little islands of activity in a calm-looking brain. They miss activity in other brain regions, however, that might be less robust but still psychologically and biologically meaningful. The little islands imply a false story of a compartmentalized human brain, with separate circuits for hate, love, fear, magic, or whatever. (And a scientist who expects to find little islands has no motivation to look further.)
If you run a study with enough power, brain scans show strikingly different, whole-brain activity. A great example is a study on attention that was published in the Proceedings of the National Academy of Sciences in 2012. Test subjects were asked to do a very simple thing in the scanner: shift their attention back and forth between two different tasks. A typical, underpowered experiment with (say) 50 trials would associate this attention-shifting with a handful of little islands in one brain network. But in this study, test subjects completed an unprecedented 500 trials each, and the resulting scans showed increased activity in over 80% of the brain.
Running a properly powered study is enormously complex. The scanning costs increase tremendously, and the poor test subjects have to lie motionless in a metal tube for about 10 hours instead of the usual two. (And the scientists, being muggles, cannot assist them by casting the “Petrificus Totalus” spell.) Plus, research scanners are always in heavy use by other scientists, so booking multiple subjects for 10-hour segments is extremely difficult, even with a magic wand.
The bottom line is that nobody has ever found a brain circuit for any emotion, including hate, that satisfies the five ordinary requirements listed above. The same goes for magical ability, unfortunately (though I am told that Ministry researchers are upgrading their scanning technology to the latest version, Pensieve 7.0).
Emotions don’t live at any set location in the brain. Instead, they are constructed by the whole brain as needed. This means you have more control over your emotions than you might think. My book How Emotions are Made: The Secret Life of the Brain has the details.