Scientists discover that humans have a hidden ‘seventh sense’

Sand has a memory of sorts. Press into a loose pile of dry grains and something moves, not just where your finger sits, but farther out, ahead of where you have not yet reached. That disturbance travels. And according to a new set of studies from Queen Mary University of London and University College London, human fingertips can read it.

The finding is stranger than it first sounds. People can detect a solid object buried beneath dry sand before their finger ever touches it, sensing its presence through pressure changes that ripple outward through the grains. The ability had never been formally tested in humans before. Researchers now have numbers to back it up, and they built a robot to see how far the phenomenon could go.

Most people think of touch as something that kicks in at the moment of contact. Skin meets surface, nerves fire, information arrives. That is the simplified version. What this research complicates is the assumption that awareness stops at your fingertip.

The inspiration came partly from biology. Shorebirds such as sandpipers and plovers hunt by pressing their bills into wet sand, detecting buried prey through tiny pressure shifts without ever seeing what they are after. Scientists at the two London universities wanted to know whether humans carry a similar capacity, one that rarely gets used because daily life seldom demands it.

To find out, they recruited twelve volunteers between 18 and 26 years old. Each person moved a single index finger through dry sand inside a covered box, guided by a strip of blinking LEDs set to pace them at two centimeters per second. Somewhere along the track, which stretched more than a meter, a five-centimeter plastic cube might be buried.

Participants pressed their fingers into the sand through a narrow slot and kept moving until something felt off. Before each trial, they touched the cube directly so that finger depth stayed consistent. On average, fingers sat about 4.8 centimeters into the sand.

The setup was deliberately boring. No visual cues. No guessing from context. Just a finger moving through grains and whatever that finger could feel.

Across 216 human trials, results held up in ways that surprised even the researchers. Participants detected buried objects 79 times without touching them. They made contact-based discoveries 35 times, recorded 30 false positives, and correctly reported no object in 58 trials.

Signal detection theory, a statistical method designed to separate genuine sensitivity from lucky guessing, produced an average sensitivity score of d' = 1.1973. That is well above chance. The response bias score came in at c = -0.112, indicating participants were not simply leaning toward saying yes to every trial. They were responding to something real.

Most detections happened roughly 2.7 centimeters before the finger reached the cube. Granular physics predicts a theoretical detection range of 6.9 centimeters, a ceiling imposed by how pressure waves move through loose material. Human performance fell short of that ceiling, as you might expect given the natural wobble of a moving finger through shifting grains. Still, precision topped 70 percent.

"This changes our conception of the perceptual world," said Elisabetta Versace of Queen Mary University of London, describing the sense as one that stretches awareness beyond direct contact.

The team did not stop at human subjects. To probe the physics more precisely, researchers built a robotic finger: a custom-designed tactile tip mounted on a UR5 robotic arm, fitted with four sensors measuring forces across three directions. The assembly matched the size of a human finger and moved through sand at the same two-centimeter-per-second pace. It completed 120 trials, including 20 with no object present.

Five machine learning models using Long Short-Term Memory networks processed the sensor data. Each model ran with a different detection threshold, ranging from three to eleven centimeters, essentially telling the algorithm how early it was allowed to call a hit. The lowest threshold gave the most balanced outcome. At that point, the robot detected a real object in every trial and avoided false alarms 90 percent of the time. Precision reached 91 percent, higher than any individual human score.

Wider thresholds extended the robot's sensing range but introduced a serious tradeoff. At the broadest threshold tested, precision dropped to zero because ordinary sand movement began triggering detections. The algorithm was treating noise as signal.

Median detection distances reflected the range-accuracy tension clearly: 2.46 centimeters for the lowest threshold, 4.43 centimeters at the five-centimeter model, and up to 12.94 centimeters for the widest. Reach increased. Reliability collapsed.

Matching the human data against the robot's seven-centimeter model put both near the predicted physical limit of sand sensing. The comparison held up numerically. But the behavioral differences were sharp.

People produced fewer false positives. They seemed to hesitate when the evidence was thin, applying something like natural skepticism to ambiguous sensations. The robot responded to the faintest force changes with full commitment, which made it exquisitely sensitive but also prone to errors when grains shifted without cause.

Lorenzo Jamone of University College London described the two sides of the study as mutually informative. The robot's design emerged from the human results, and the robot's detailed force data helped researchers revisit what the human participants had actually been feeling. Psychology, robotics, and machine learning stitched together into a single line of inquiry.

PhD student Zhengqi Chen, involved in the robotic component, noted that the findings open paths toward assistive tools; systems that let people or machines sense through loose material without disturbing it, locating things that cannot be seen.

The practical territory here is genuinely wide. Robots equipped with this kind of tactile awareness could assist archaeological teams by identifying buried objects before any physical excavation begins, reducing the risk of damage to fragile artifacts.

After structural collapses or disasters, search and rescue machines could probe rubble for hazards or survivors using touch rather than cameras. In planetary exploration, where dust, low visibility, and unpredictable surface textures are constant challenges, tactile sensing could serve as a primary navigation tool on Mars or icy moons.

Even closer to home, the research raises quieter questions about human perception. The volunteers in this study had no training. They were not specialists. They simply moved their fingers through sand and, more often than chance alone could explain, they felt what was coming.

Research findings are available online in the journal IEEE Xplore.

The original story "Scientists discover that humans have a hidden 'seventh sense'" is published in The Brighter Side of News.

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