Everyone knows that when you hold a compass in your hand the needle will point north thanks to Earth’s magnetic field, but aside from simple navigation you probably don’t spare much thought for our planet’s magnetism. However, that doesn’t mean that your body isn’t still sensing the geomagnetic forces, and a new study suggests that humans, like many other animals, can indeed sense the magnetic field.

The research, which was carried out by scientists at Caltech, reveals that humans have what might be described as a subconscious ability to detect geomagnetic forces. Whether that ability played a role in our past or if it’s still influencing us today is a much more difficult question to answer.

The debate over whether humans can sense Earth’s magnetic field has been happening in science circles for decades. Many past experiments relied on the actions or behavior of participants in order to draw a conclusion, but Caltech’s technique was more straightforward, using EEG brain scans to see how a person’s brain reacts to geomagnetic forces.

Dozens of participants were placed in a Faraday cage — an enclosure designed specifically to block external magnetic fields — and then subjected to magnetic forces that the researchers could control themselves. This allowed the scientists to see exactly how the brains of the volunteers reacted to changes in the magnetic field without any external influence.

What the team found was that while the participants said they didn’t actively feel any changes happening, their brains were telling a different story.

“The brains were ‘concerned’ with the unexpected change in the magnetic field direction, and this triggered the alpha-wave reduction,” the researchers explain. “That we saw such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception.”

Put simply, our brains definitely monitor magnetic fields even if we don’t realize it. The fact that our brains can sense geomagnetism isn’t a huge shock, as many species actively use magnetic fields for navigation, but we still don’t know whether that information is being used by our brains in any meaningful way. It’s even possible that our brains’ reactions are a leftover from ancient ancestors that did actively use geomagnetism, but that would be very difficult to prove.