Your Choices Can Be Seen in Your Brain Before You’re Conscious of Them

This week in science: taking nutritional supplements can't prevent depression, a video of a droplet doing something you've never seen water do, and researchers predicted people’s choices before they made them.
March 8, 2019, 8:26pm
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Each week, we read what's going on the world of science and bring three of the wildest findings straight to you. Scroll through for the latest:

Scientists can predict your choices before you’re consciously aware of them

In the early 1980s, a neuropsychologist named Benjamin Libet did an experiment that muddied the concept of free will, or the idea that we have agency and control over our actions. We generally believe that first we think something, and then we do it. But Libet found that when he asked people to decide to perform a simple task, like moving their hand, their brains showed electrical activity before they were conscious of making the choice to move. His findings proposed that maybe our brains are unconsciously driving our choices, and we just believe it is our thoughts leading to actions after the fact.

Since then, more studies have shown that your decisions can be read from your brain before you’re conscious of them. “The commodious literature on voluntary actions makes it quite clear that we are less free than we think we are, that our prior actions, beliefs and habits shape us in untold ways,” neuroscientist Christof Koch, said in an interview in Scientific American.

In a new study in Scientific Reports, there’s now more evidence of this phenomenon. Researchers from the University of New South Wales in Sydney found they could predict choices that people were asked to think about 11 whole seconds before their subjects consciously chose what to think about.

People were asked to choose between two visual patterns—one was red and one was green, with vertical or horizontal stripes—and then asked to imagine them while getting their brains scanned in an fMRI machine. The researchers recorded their brain activity before, during, and after the decision.


“To our surprise, brain activity from before the decision allowed us to predict future decisions up to 11 seconds before they were made and also predict how strong or vivid the thoughts were,” says Joel Pearson, a cognitive neuroscientist and senior author on the paper.

The parts of the brain where they saw activity were in the “executive areas of the brain—where our conscious decision-making takes place—as well as visual and subcortical structures,” a press release says. Pearson says it’s possible that when faced with a choice, the brain has pre-existing thoughts on “standby,” which can influence our decisions unconsciously.

“In other words, non-conscious, hallucination-like patterns seem to emerge that bias what you choose and think,” he tells me.

We might make decisions based on which thought trace is the strongest, he says. But for now, it’s unclear if more complex decisions, like choosing at item for lunch or picking a movie, are solved in the same way. But their results do show that preconscious mental images can influence our future thoughts to some extent.

There is previous work showing that external forces can bias our associations and choices; if you show someone a dollar bill, that will lead them to associate the word “bank” as a place for money, rather than a riverbank. “This kind of external priming has been shown hundreds of times, so what we are talking about here is something perhaps similar, but completely internal: the unconscious hallucination is priming decisions,” Pearson says.

Does this mean our brains make our choice before we have any conscious input? That’s one way to look at it, but there’s another that lets us hang onto some semblance of agency.

“Another interpretation, that we prefer, is that the choice was primed or biased by unconscious mental images/hallucinations,” Pearson says. “The difference is subtle, but the latter would mean that the choice and the unconscious images are dissociable, [or separate] processes, ultimately leaving some room for free will.”

Vitamin supplements won’t prevent depression

From my unscientific observation of Instagram ads and grocery store aisles, I’ve decided that we, as a culture, have gone supplement crazy. There are wellness products that promise everything under the sun, including that they can help with our growing mental health needs.

But a new study in the Journal of the American Medical Association (JAMA) found that supplements alone cannot prevent depression. There is epidemiological evidence that links diet and nutrition to depression, says Ed Watkins, a professor of experimental and applied clinical psychology at the University of Exeter in the UK, and author on the paper. But since that data is only correlational, he and his colleagues wanted to see if taking supplements was actually causing less depression, or if less-depressed people tended to eat more healthily.

They looked at more than a thousand overweight or obese people who weren’t currently depressed, but were at risk for depression. Half of the subjects got nutritional supplements, like folic acid, vitamin D, omega-3 fish oils, zinc, and selenium, while the other half were given a placebo, and the researchers followed up with them after one year.

“The supplements had no effect at all on depression,” Watkins tells me. “If anything, the placebo pill was more helpful.”

Some of the participants also got therapy focused on assisting them adopt healthy habits. The therapy also wasn’t able to prevent depression overall, but “there was some evidence that it prevented depressive episodes in those participants who attended a recommended number of sessions,” a press release says.

So go ahead—drink your adaptogenic latte while getting a B12 shot infusion, but don’t expect it to provide a miracle prevention for depression. “Taking the supplements themselves is unlikely to be a problem for an individual, although it is expensive to buy these over the counter so it would be a lot of money spent for no benefit on depression,” Watkins says. “The concern would be if people thought that taking supplements was an alternative to the existing proven treatments, and thus missed out on active treatment.”

A droplet that doesn’t just splash, but “gyrates”

File this under things I’ve never thought too much about: what happens when a droplet of liquid hits a hard surface. According to a new paper in Nature Communications, being able to manipulate “droplet-sold impacting behaviors” is important for a lot of things, like anti-icing, ink-jet printing, or self-cleaning. What a droplet does when it hits a surface depends on the properties of the sold it’s hitting. In this study, researchers showed that they could manipulate these factors so that “an impacting droplet can be converted to gyration, with a maximum rotational speed exceeding 7,300 revolutions per minute.” The findings, they wrote, open up more possibilities of controlling liquid motion. Woah.

Video from Huizeng Li et. al. S__pontaneous droplets gyrating via asymmetric self-splitting on heterogeneous surfaces. Nature Communications.

Your weekly science and health reads

Selma Blair's MS diagnosis reveals battle chronic illness sufferers like me fight to be taken seriously. By Caira Conner in NBC News.
“She has also highlighted a particularly sticky and frequently gendered issue felt acutely by those of us with chronic illness who can struggle for years to get the medical profession to even acknowledge something is amiss.”

How breast size affects how women exercise. By Gretchen Reynolds in The New York Times.
A study found that the bigger a woman’s breasts are, the lower her participation was in physical exercise, especially if it was vigorous.

The twins that are neither identical nor fraternal. By Sarah Zhang in The Atlantic.
A cool story that introduced me to a new favorite word: “sesquizygotic twins.”

Neuroscience Readies for a Showdown Over Consciousness Ideas. By Ryan Garcia in Quanta.
A one-stop shop to get the scoop on the leading theories of consciousness right now.

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