Right Wingers and the Reptile Brain

If you happen to be of the left-leaning persuasion, I imagine that you will find the results of this recent study quite satisfying. Researchers in the UK asked test subjects about their political leanings, and then scanned their brains. Guess what? They found that liberals tended to have more volume in an area of the brain called the anterior cingulated cortex (ACC), a region associated with, among other things, decision making. Conservatives, on the other hand, showed more heft in the amygdala, the region associated with emotional memory and in particular with the processing of fear. Writes Time magazine:

These structural differences, the authors suggest, support previous reports of differences in personality: liberals tend to be better at managing conflicting information, while conservatives are thought to be better at recognizing threats, researchers said. “Previously, some psychological traits were known to be predictive of an individual’s political orientation,” said [lead researcher Ryota] Kanai in a press release. “Our study now links such personality traits with specific brain structure.”

If you wear Tevas and clothes made out of organically grown hemp, this will seem intuitively obvious. After all, liberals arrive at their views through logical reasoning, while conservatives operate on a purely emotion-driven level, like reptiles. Right?

 Not so fast. Even if this study turns out to be replicable, there’s a fundamental problem in the underlying logic — namely, the supposition a brain region that’s bigger in size will exhibit correspondingly greater activity of the type generally associated with it. In fact, the exact opposite may be the case. Greater size might be an indication of less activity.

Indeed, the very same researcher, Ryota Kanai of the University College London, has even more recently found another compelling correlation between brain-region size and mental function – but it works in exactly the opposite way! This time, Kanai’s team was exploring the brain anatomy of people who are easily distracted. As the New Scientist recaps:

To investigate distractibility, the team compared the brains of easy and difficult-to-distract individuals. They assessed each person’s distractibility by quizzing them about how often they fail to notice road signs, or go into a supermarket and become sidetracked to the point that they forget what they came in to buy. The most distractible individuals received the highest score. The team then imaged the volunteers’ brains using a structural MRI scanner. The most obvious difference between those who had the highest questionnaire scores – the most easily distracted – and those with low scores was the volume of grey matter in a region of the brain known as the left superior parietal lobe (SPL). Specifically, the easily distracted tended to have more grey matter here.

The SPL is a region that seems to assist in top-down executive control of one’s attention. That is to say, when it’s functioning is disrupted, a person has a very hard time focusing on one thing. Their attention wanders all over the place, like a toddler in a toy store. To demonstrate this correlation, Kanai’s team had test subjects perform a simple task while ignoring a persistent distraction – then disrupted the function of their SPL using a technique called transcranial magnetic stimulation. Sure enough, the subjects with disrupted SPL function took 25 percent longer to complete the task.

Okay, so here’s the tricky part. How does Kanai explain that the brain region used for self-control of attention is actually larger in the subjects whose minds tended to wander? His answer is to suggest that the problem may lie in immaturity. The New Scientist:

Kanai speculates that it may be linked to that fact that as we mature, the brain’s grey matter is pruned of neurons in order to work more efficiently. He suggests that a greater volume of grey matter may indicate a less mature brain, perhaps reflecting a mild developmental malfunction. “This theory would fit in with the observation that children are more easily distracted than adults,” Kanai says.

I find that suggestion eminently plausible – but also suspiciously convenient, given that so recently Kanai was finding that increased size explained increased mental functioning. For my money, an equally valid take-home lesson from the distraction study would be that we shouldn’t look for any simple connection between the size of a brain region and the relative success of its functioning.

This confusion reminds me of one of my favorite biological parables. When I was 16 I had the good fortune to spend a year studying at the King’s School in Canterbury, England. My favorite class was Biology, thanks to my wonderfully witty, erudite and humane teacher, Mr Wilkinson. One of his lessons remains vivid to me to this day. When he was young, he told us, the milkman used to deliver cereal as well as dairy. Being quite fond of cornflakes, Mr Wilkinson put in for the delivery of a regular order. But as tends to happen, his ardor for that particular product began to dim over time. He ate less and less of it. And still the boxes of corn flakes kept coming, until they were lined up on top of every horizontal surface in his kitchen. “Wow, you must like cornflakes,” visitors would invariably exclaim, upon seeing this culinary trove. “Can’t stand ‘em,” Wilkie would reply. “That’s why I’ve got so much.”

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