There are two different ways we might navigate from place to place: we either remember landmarks along the way, or we note how far we go in each direction, and what turns we’ve made along the way. The landmark system doesn’t work very well in nondescript landscapes or in the dark, and the second system—which mariners term “dead reckoning,” is susceptible to increasing errors as the distance we travel increases. So in day-to-day life, walking or driving around town, which method do we use?
A team led by Florence Gaunet explored this issue using a driving simulator. The participants in the experiment “drove” through virtual city streets in one of three ways. The active group actually controlled their path using a joystick, following directions given to them by an experimenter. The passive group took the same path, but had no control over their direction; instead the simulator simply propelled them along. Finally, the snapshot group was shown static images from along the journey, roughly every 2 seconds, approximating the same speed of travel as the other groups.
Gaunet and her colleagues tested how well participants knew where they had gone in three different ways: by showing snapshots from along the journey (these weren’t necessarily the identical views the snapshot group had seen) and asking whether they had passed through that spot; by asking them to point back towards the starting position of their journey, and by asking them to draw the path of their journey on a piece of blank paper.
The first two tests revealed no differences between any of the groups. The group that had only seen snapshots was as accurate as the other groups, even when the snapshot they viewed wasn’t one they had seen before. All three groups were equally accurate when asked to use the joystick to orient the simulator so that the virtual observer was facing towards the starting point.
It was only the drawings were analyzed that differences between the groups began to emerge. There was no significant difference between the maps drawn by either active or passive observers of the smooth animation. However, the snapshot viewers made large errors in their maps, transforming gradual corners into sharp ones, modifying irregular angles to 90-degree turns, and making significant mistakes in the total distance traveled.
Gaunet et al. don’t claim that their data provides a definitive answer as to whether we navigate by landmarks or dead-reckoning; however, it is clear that when we only see a slide show of a trip, our ability to make a map is impaired—thus, we’re getting important information about our location from the sensation of motion, suggesting that dead-reckoning is an important aspect of how we get around.
Gaunet, F., Vidal, M., Kemeny, A., & Berthoz, A. (2001). Active, passive and snapshot exploration in a virtual environment: Influence on scene memory, reorientation and path memory. Cognitive Brain Research, 11, 409-420.