Human

The mystery of the ninth sense

 By Eniday Staff

“I’ve got a sixth sense!” How many times have we all said that when we just feel something in the air, or get a sense of foreboding about how our friends, family or colleagues are going to act? Of course, we all know that there is no sixth sense and no organ to detect it…

More than anything else, the sixth sense is probably an interpersonal trait, an ability to pick up information, often non-verbal, from other people. So, we are aware that there are five senses and that’s all there’ll ever be. We’ve all known them since nursery school: sight, hearing, smell, taste and touch. Each one has its own organ: the eyes, ears, nose, mouth and skin. On the face of it, it all seems pretty obvious. But how sure are we? Is there in fact something eluding us in our daily lives, an extra sense (or maybe even senses) that we don’t realise we have? What if, like pigeons, we’ve got a sense for detecting the earth’s magnetic field, but we just don’t know it?
This is the conclusion of a group of researchers at Caltech, the California Institute of Technology, published in the latest edition of eNeuro, one of the most authoritative and widely read international journals on neuroscience. According to these researchers, the human organism has a system for detecting the position of the body with respect to the direction of the earth’s magnetic field. This means that we effectively have a sort of compass inside us, that can detect changes in the field surrounding us in various ways.

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Sensory areas of our brain (BSIP/UIG, Getty Images)

Five senses… plus three

Before getting into the details and explaining how the California scientists reached this hypothesis, we must address something. If their discovery is confirmed, we wouldn’t be talking about a sixth sense, but more likely a ninth, for the simple reason that the senses our brain uses to receive information are not limited to five. This could make the findings published in eNeuro even more plausible. Other than the famous five senses, there are three more that are less well-known and less obvious but work excellently. They are thermoception, nociception and proprioception. These three neural systems are not localised in one part of the body, like the five senses we normally think of, but spread all through the human organism. In truth, one of the classic five senses, touch, shares this characteristic. Without wishing to do a disservice to the countless philosophers and naturalists who’ve spent the last 25 centuries pondering this, we could take an example that all of us have experienced once in our lives. When you touch an object or any other thing with one finger or another, you don’t sense many differences. If you touch an orange with your eyes closed, or with your right hand instead of your left, you’ll still recognise it. If you touch it with your foot or your elbow, though, you’ll have no idea what it is. So, touch is spread in a very varied way, highly active on the fingertips and almost absent on the back.
Thermoception also works through the skin, but using a completely different system of transmission. The neurons that tell us when our sauce is burning aren’t the same ones that tell us if that’s an orange we’re touching (or swallowing). The same is true for nociception, the sensation of pain that’s transmitted from the body’s outer layer, through specific sensors and channels, to our brain.

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Birds use Earth's magnetic field to navigate the globe. The magnetic field is a result of the movement or convection of liquid iron in the outer core. As the liquid metal in the outer core moves it generates electric currents, which lead to a magnetic field

The ninth sense

And magnetoception? Before getting into that, we should think about proprioception, which is about sensing our body in its entirety and its movements. Everyone knows when their arm’s moving or their head’s turning. But where is proprioception located? In truth, not very much is known about that. There are sensors in the muscle and joint structures, but it’s still not at all clear how the information they receive ends up creating such a sophisticated map of the body. The same could be true of magnetoception. The tests that have been carried out to prove its existence involve lying people down inside a two-metre cube without light. During the test, which lasts an hour, the direction of the magnetic field, generated by a system of conductive networks surrounding the cube, is continuously altered. The test’s subjects wear an electroencephalographic helmet that allows changes in their brain activity based on the direction of the field to be observed. At the end of the test, none of the subjects can say they’ve felt the alterations, but in more than half of cases, the encephalographic equipment records a change in brain activity. Despite these small revelations, no one has any idea yet how the brain registers these alterations, any more than they do about how migratory birds and pigeons orient themselves when flying. In the past, it was thought they had nerve endings containing metal oxides, but that hypothesis has been refuted. So, for now at least, some mysteries of nature remain.

READ MORE: How AI can read your personality by Agata Boxe

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Eniday Staff