1. What Happened When the Sun Went Behind a Cloud
You have probably seen it in a movie: lost travelers stumble across their own footprints and realize they have been going in circles. Until 2009, that idea rested mostly on stories. A team at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, led by Jan Souman and Marc Ernst, decided to test it with GPS trackers [1].
Volunteers walked for several hours in the Sahara in Tunisia and in the Bienwald forest in Germany, trying to walk as straight as they could. When the sun or moon was visible, they kept a fairly straight path. When the sun disappeared behind clouds, they started walking in circles without noticing [1]. So the "going in circles" story is real. The next question is what pushes a walker off course.
2. Why Small Sensing Errors Add Up to a Circle
The same team also asked people to walk blindfolded. Most of them walked in circles, and some of the circles were smaller than 20 meters across [1].
A popular guess is that one leg is longer or stronger than the other. The data did not fit that guess. The same person sometimes veered left and sometimes right, and a leg difference would pull a person toward the same side every time [1].
The researchers' explanation is that the senses that tell the brain which way we are heading carry small random errors. Those errors accumulate, so a person's feeling of "straight ahead" slowly drifts away from the real direction. Faraway landmarks or the sun give the brain something to check against, which stops the drift [1]. A simple way to picture it is a compass needle that wobbles a little more with every step, until something outside lets you reset it.
This comes from a research group's own press release, and it does not say which body signals matter most. But it explains why getting lost is not only about not knowing the way. Even when we are sure we are going straight, our sense of direction needs help from the world around us. So how does the brain keep track of where we are in the first place?
3. Cells in the Brain That Work Like a Positioning System
In 1971, John O'Keefe found a type of nerve cell in a brain area called the hippocampus that became active whenever a rat was at one particular spot in a room. Other cells fired at other spots, which led O'Keefe to conclude that these "place cells" form a map of the room [2].
In 2005, May-Britt Moser and Edvard Moser discovered a second kind, "grid cells," which form a kind of coordinate system the brain uses to represent position [2]. The three scientists shared the 2014 Nobel Prize in Physiology or Medicine for these discoveries, which the Nobel committee described as an "inner GPS" in the brain [2].
Place cells and grid cells help explain how the brain can remember where things are. They do not make us immune to drifting when there are no landmarks. Does the way we use this system change it?
4. What London Taxi Drivers' Brains Suggest About Practice
London has a famously tangled street layout, and its licensed taxi drivers have to learn it in great detail. In a study published in 2000, a University College London team compared MRI brain scans of licensed taxi drivers with scans of people who were not taxi drivers. The drivers had a larger posterior (rear) part of the hippocampus, while a more anterior (front) part was larger in the comparison group [3].
The longer someone had worked as a taxi driver, the larger the rear hippocampus tended to be, and the smaller the front part tended to be. The authors suggested that the rear hippocampus stores a map of the environment and can change in response to the demands of navigating [3].
There is an important limit. The study compared groups at one point in time. It shows that driving experience and hippocampal size go together, but a scan like this cannot prove that driving caused the change, or that every taxi driver has a great sense of direction. If experience can shape this brain region, what happens when more of the work of finding the way is handed to a device?
5. Does Using GPS All the Time Weaken Our Own Sense of Place?
In 2020, Louisa Dahmani and Véronique Bohbot at McGill University in Canada studied 50 regular drivers. They measured each person's lifetime GPS experience and tested spatial memory in virtual navigation tasks. People with more lifetime GPS use did worse on spatial memory when they had to find their way without GPS [4].
Thirteen of the participants came back three years later. Those who had used GPS more during those three years showed a steeper decline in hippocampus-dependent spatial memory. People who used GPS more did not report having a poorer sense of direction to begin with, which the authors read as a sign that heavy GPS use may have come before the decline, rather than the other way around. This design cannot confirm cause and effect [4].
Thirteen people is a very small group, and the authors themselves call the follow-up sample small [4]. The result is a warning sign, not proof that GPS harms the brain. It fits with the idea from the taxi drivers: practice at building mental maps seems to matter. What can we do about it on an ordinary walk?
6. A Safe Way to Test Your Own Mental Map
Here is a small experiment that needs no blindfold and no unfamiliar places. Pick a short, familiar walk with an adult, such as the way to a park. Before you start, choose three landmarks, for example a corner shop, an unusual tree, or a bright red door. Say their names out loud as you pass each one.
When you get home, draw the route from memory without looking at a map, marking the landmarks in order and the places where you turned. Then compare your drawing with a real map. Count separately how many turns you got right and how many landmarks you put in the right order. That shows which part of your mental map is strongest. This activity is only an idea inspired by the research above. It is not a method tested in the studies, and one try cannot tell you anything about your brain.
Please do not try walking with your eyes closed outdoors. The Max Planck team's walks were done with researchers in open, safe areas, and it is easy to trip or bump into things. If you want to read the originals, start with the Max Planck press release [1], which is short, and then the abstract of the GPS study [4], where you can see how few people were retested.