Scientists Can Read Your Mind Before You Know You've Made A Decision


Stephen Luntz

Freelance Writer

clockMar 6 2019, 15:55 UTC

By looking at the pattern of the areas that light up in the brain, scientists can not only get a crude idea of what you are thinking, but what you will be thinking before you know it. MriMan/Shutterstock

It's not quite Minority Report, but scientists can sometimes see your decisions before you know them yourself. When participants in a study were asked to choose between two patterns, the scientists running the test used images on an fMRI machine to foresee which they would choose. The researchers consider this evidence that our decisions are primed by an unconscious “stand-by” mode.

Professor Joel Pearson of the University of New South Wales asked a group of volunteers to imagine a pattern of either horizontal or vertical colored lines.


When they had decided which they would visualize, the participants pressed a button. They later pressed other buttons to indicate how strong the image was. Pearson was able to verify the timing of the decision using the imaging to ensure people were not simply delaying pressing the button. Nevertheless, more often than not, Pearson and his team already knew the outcome.

Each line orientation matched specific patterns in the visual cortex. Moreover, Pearson reports in Nature, these patterns frequently showed up beforehand, by up to 11 seconds, indicating the participants' brains were predisposed to one orientation or the other before they consciously knew what they'd do.

Some participants were shown these two images and asked to choose. Others were shown a verticle green/horizontal red pairing. Future Minds Lab

Pearson told IFLScience some media reports of the study have described it as showing we lack free will; that decisions we think we are making are predetermined. He added some researchers, who have conducted somewhat similar experiments, endorse this idea, but he rejects it. The accuracy of predictions prior to the decision was only a little over 50 percent in some trials – sufficient to prove the effect was real, but even the most successful trials did not approach the 100 percent we would expect if free will was absent.


Instead, Pearson described what is occurring as priming. “If I asked you to imagine a bank,” he told IFLScience, “you might think of something where you put money. But if I showed you an image of water first, you'd be more likely to think of a river bank.” He thinks something similar is happening here, but the priming is internal, only made visible by the fMRI.

The researchers were also able to predict participants' rating of image strength, which fluctuated over repeated trials, based on the timing of when relevant brain regions formed patterns.

Overall, participants thought of the vertical and horizontal lines almost exactly equally often, although there was a slight bias in favor of the opposite orientation to the previous trial.


The team hopes the work will help explain the workings of post-traumatic stress disorder (PTSD), noting that people who suffer from it “report a complete lack of control of both the content and strength of their mental imagery.”