People have access to map-like characters in their memory, usually oriented towards north, which helps them cruise around the city, researchers say.
Some theories of how we locate ourselves in place and space posit that each of us creates a personal "global reference frame," constructed of environmental factors (a city's grid, a cathedral visible everywhere in town) and individual experience, such as where we live in town.
Others say we orient ourselves depending on where we are �parallel to the street we're on.
According to either of these theories, the further away an invisible location is, the longer it takes us to point in its direction and the more likely we are to make a mistake.
However, the study by authors, Julia Frankenstein, Betty J. Mohler, Heinrich H. Bulthoff, and Tobias Meilinger, who collaborated at the Max Planck Institute for Biological Cybernetics, in Tubingen, Germany, does not support these theories.
"Our memory for our city of residence shows a map-like character," said Meilinger, a research scientist at the institute.
"And that map seems to be oriented towards the north.
"At least in western societies, where maps are north-oriented, and people usually use maps and are able to read them, they can -and will- rely on their memory of city maps for certain spatial tasks."
The study took into consideration 26 residents of Tubingen (who had lived in Tubingen for at least two years), who were put into a virtual-reality headset and seated in a chair that didn't allow them to swivel.
Participants found themselves in the virtual three-dimensional photorealistic model of their hometown, at locations familiar to them, surrounded by fog masking all but the near distance.
Then they had to point to an invisible location �say, the main gate of the university or the fire station. The scenes changed, and so did the participant's spatial orientation.
After 60 three-location trials, participants were asked to draw a map of the town including all the locations they'd pointed to.
The results showed that although participants drew differently oriented maps, everyone performed most accurately when facing north and got worse the further they deviated from north.
The only explanation the researchers could figure was that they had all seen, and internalized, a map of Tubingen at some point, and Western maps are all oriented the same way �north on top.
Meilinger conjectured that we rely on this mental map out of cognitive laziness.
"If you acquire your knowledge from navigation only, the task [of pointing to an invisible target] requires you to coordinate a lot of things into the same reference frame � walked trajectories, experienced views, and so on."
"A map gives all that information within one frame."
Frankenstein further said that the memory of a map does not "need to be updated by further experience, as it depicts all spatial relations undistorted within one reference frame."
"It therefore provides a very reliable source of spatial information," she said.
"Remembering a map is not the only strategy to solve spatial tasks. We do not necessarily get lost in environments where we have never seen a map of- e.g., buildings or our flat."
And while participants used the map for pointing, the replication of the map (i.e., drawing a map) did not result necessarily in north-oriented maps.
"Our brain seems to choose the easiest and best strategy to solve spatial tasks, but relying on a mental city-map is one of them," Frankenstein added.
The study has been published in Psychological Science, a journal by the Association for Psychological Science.