The ability to sense the Earth’s magnetic field—a trait known as magnetoreception—is well documented among many animals, but researchers have struggled to show that humans are also capable of the feat. Until now.

New experimental evidence published today in the science journal eNeuro suggests the human brain is capable of responding to the Earth’s magnetic field, though at an unconscious level. It’s not clear if our apparent ability to sense the magnetic field is in any way useful, as it’s likely a vestigial trait left over from our more primitive past. Giving the new finding, however, researchers should investigate further to determine if magnetoreception is somehow contributing to our behavior or abilities, such as spatial orientation.

Magnetoreception is found among both invertebrates and vertebrates, and it’s probably a capacity that’s been around for a very long time. Some bacteria and protozoans exhibit magnetoreception, as do some migratory birds and sea turtles, who use the added sense to assist with navigation. Dogs are also sensitive to the Earth’s magnetic field, orienting their bodies along the North-South axis when they poop.

Around 30 years ago, scientists tried to determine if humans have a similar capacity, but to no avail. These pioneering efforts produced results that were either inconclusive or unreproducible, so scientists largely gave up, figuring magnetoreception is something outside the human realm. In the years that followed, work on animals increasingly pointed to magnetoreception as the result of complex neurological processing—a possibility that motivated Caltech geophysicist Joseph Kirschvink and neuroscientist Shin Shimojo to revisit the issue.

“Our approach was to focus on brainwave activity alone,” Kirschvink told Gizmodo. “If the brain is not responding to the magnetic field, then there is no way that the magnetic field can influence someone’s behavior. The brain must first perceive something in order to act on it—there is no such thing as ‘extra-sensory perception.’ What we have shown is this is a proper sensory system in humans, just like it is in many animals.”

To test whether the human brain is capable of magnetoreception, and to do so in a reliable, believable manner, Kirschvink and Shimojo set up a rather elaborate experiment involving a chamber specially designed to filter out any extraneous interference that might influence the results.

Illustration of the experimental setup.
Image: C. Bickel

The isolated chamber, within which participants had their brainwaves monitored by electroencephalogram (EEG), was housed inside a Faraday Cage, which shielded all interior contents from external electromagnetic fields. Three orthogonal sets of square coils, called Merritt coils, allowed the researchers to control the ambient magnetic fields around a participant’s head. Acoustic panels on the wall reduced external noise from the building, while a wooden chair and isolated floor prevented any unwanted interference with the magnetic coils. A battery-powered EEG was placed next to the participant, which was connected to a computer in another room with an optical fiber cable.

During carefully controlled experiments, participants sat upright in the chair with their heads positioned near the center of the magnetic field, while EEG data was collected from 64 electrodes. The hour-long tests, in which the direction of the magnetic fields were rotated repeatedly, were performed in total darkness. The experiment involved 34 adult volunteers, who collectively participated in hundreds of trials; all tests were done in a double blind manner, and control groups were also included.

After the experiments, none of the participants said they could tell when or if any change to the magnetic field had occurred. But for four of the 34 participants, the EEG data told a different story…Read More at