But can we navigate by it? Science News reports on the new finding that, like birds, humans appear to have “magnetoreception abilities,” sensing directions by detecting patterns in our planet’s magnetic field that alter our brain waves:
Now, by exposing people to an Earth-strength magnetic field pointed in different directions in the lab, researchers from the United States and Japan have discovered distinct brain wave patterns that occur in response to rotating the field in a certain way.
These findings, reported in a study published online March 18 in eNeuro, offer evidence that people do subconsciously respond to Earth’s magnetic field — although it’s not yet clear exactly why or how our brains use this information.
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During the experiment, 26 participants each sat with their eyes closed in a dark, quiet chamber lined with electrical coils. These coils manipulated the magnetic field inside the chamber such that it remained the same strength as Earth’s natural field but could be pointed in any direction. Participants wore an EEG cap that recorded the electrical activity of their brains while the surrounding magnetic field rotated in various directions.
This setup simulated the effect of someone turning in different directions in Earth’s natural, unchanging field without requiring a participant to actually move. (Complete stillness prevented motor-control thoughts from tainting brain waves due to the magnetic field.) The researchers compared these EEG readouts with those from control trials where the magnetic field inside the chamber didn’t move.
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Sure enough, changes in the magnetic field triggered changes in people’s alpha waves. Specifically, when the magnetic field pointed toward the floor in front of a participant facing north — the direction that Earth’s magnetic field points in the Northern Hemisphere — swiveling the field counterclockwise from northeast to northwest triggered an average 25 percent dip in the amplitude of alpha waves.
Curiously, people’s brains showed no responses to a rotating magnetic field pointed toward the ceiling — the direction of Earth’s field in the Southern Hemisphere. Four participants were retested weeks or months later and showed the same responses.