We've all heard survival stories of people being lost in the wilderness saying they felt like they were walking in circles when trying to find their way. Although previously unsubstantiated by empirical data, it's a common belief that has widely permeated popular culture.
However, researchers have now tested the ability of humans to walk on a straight course through unfamiliar terrain in two different environments that included a large forest area in Germany and the Sahara Desert in Tunisia.
Results from this research provided the first empirical evidence that humans actually do tend to walk in circles when traversing unfamiliar terrain without reliable directional references.
If such directional references such as landmarks or the solar azimuth are present, people can
maintain a fairly straight path, even in an environment riddled with obstacles such as a forest.
The solar azimuth is a way to describe the direction of the sun in the sky.
The azimuth itself is not a shadow on the ground; it's a measurement of direction that helps us understand where the sun is located at any given time of the day. To visualize the azimuth, think of standing in one spot and drawing a circle around you on the ground with a stick. This circle represents the horizon.
Now, imagine dividing this circle into 360 degrees, starting from the north (0 degrees), and moving clockwise:
The azimuth is the angle between the direction you're facing (north) and the direction of the sun along this circle. For example, if you face north and the sun is in the east, you turn 90 degrees to your right to face the sun, so the solar azimuth is 90 degrees.
As you can see in the figure below, it seems that there is little systematic deviation from a straight trajectory when the sun or the azimuth is visible.
Figure: Normal Walking Trajectories. (A) Bienwald forest (Germany) (B) Sahara desert (Tunisia).
As demonstrated in the figure above, their actual trajectories deviated little from a straight line, especially in the forest, suggesting that participants were able to at least partially compensate for the change in solar azimuth. Compensation may be based on an internal click, or on additional visual cues such as local landmarks to maintain a fixed course.
It is plausible that rather than using the sun itself, participants may have used the shadows cast by it to orient themselves, because they rarely looked up to the sun.
Veering was more pronounced in the desert than in the forest when the sun was visible. This may have been due to the larger changes in solar azimuth in the desert or by the availability of additional visual cues in the forest. Essentially, these results reinforce the importance of having reliable visual cues for navigation, such as easily recognizable landmarks, the sun, or the moon.
Biomechanical asymmetries do not explain the direction into which people veer when walking blindfolded, let alone when walking with vision.
This research also failed to find a correlation with functional asymmetries such as handedness or footedness. One reason for the lack of correlation between veering behavior and asymmetries may be that the body adapts to them by using visual and other sensory information to calibrate the motor system. Hence, it is unlikely that these asymmetries play a significant role when people walk in uneven terrain with visual feedback about the direction in which they are walking.
The fact that participants often walked in circles instead of following a random zigzag path suggests that the veering from straight ahead was caused by a change in their subjective sense of straight ahead rather than by random noise in either the sensory input or the motor output.
The recorded walking trajectories show exactly the kind of behavior that would be expected if the subjective sense of straight ahead were to follow a correlated random walk(2).
With each step, a random error is added to the subjective straight ahead, causing it to drift away from the true straight ahead. As long as the deviation stays close to zero, people walk in randomly meandering paths. When the deviation becomes large, it results in walking in circles.
This indicates that circles are not necessarily an indication of a systematic bias in the walking direction but can be caused by random fluctuations in the subjective straight ahead resulting from accumulating noise. Provided that no information about the absolute direction is available for recalibration, the internal estimate of straight ahead becomes increasingly unreliable.
This drift in the subjective straight ahead may be the result of accumulating noise in all components of the sensorimotor system.
The vestibular system is known to be easily biased in one direction or the other. Asymmetric vestibular stimulation, by caloric or galvanic stimulation (i.e., medical procedures that use different stimuli to evaluate the body), has been shown to cause people to veer from a straight path(3).
Similarly, vestibular disorders affect the amount of veering during blindfolded walking(4).
Alternatively, the drift from straight ahead might originate in the motor system. It has been proposed that hemispheric differences in the dopaminergic neurotransmitter system cause systematic veering from a straight path.
Regardless of the source of the veering behavior, the blindfolded walking data show that veering is not the result of a constant directional bias but is more likely to be caused by random changes in the subjective sense of straight ahead. When walking with vision, visual information can be used to recalibrate the subjective straight ahead, making the trajectories less curved. In addition, vision allows for the use of
cognitive strategies, such as the use of landmarks.
This research demonstrates that humans tend to walk in circles when no external directional references are available. If such cues (e.g., the solar azimuth) are present, people can maintain a fixed course.
However, in emergency situations, where one's life depends on the ability to navigate through unfamiliar terrain and reach safety, panicked emotional states and group dynamics may cause these cues and more cognitive navigation strategies to be disregarded, making people walk in circles
even in the presence of reliable directional cues.
These results indicate that the seemingly simple act of walking in a straight line involves a complex interplay of various sensory modalities, the motor system, and cognition.
Understanding the solar azimuth can help you navigate unfamiliar terrain in the wilderness by using the sun as a reference point, even in the absence of landmarks. By knowing the approximate position of the sun at different times of the day, you can figure out the cardinal directions (north, south, east, west), estimate the time of day, and determine a direction to travel.
For example:
By understanding and using the solar azimuth, if you're lost you can orient yourself and make more informed decisions about which direction to travel, reduce your chance of walking in circles and increase your chances of finding your way.
Whether in the wilderness or daily life, feeling lost can be a stressful experience.
Understanding how to reduce stress can be a huge factor in helping you make more accurate decisions. Fortunately for us there is are simple breathing techniques that are proven to reduce stress quickly.
You can learn more about these powerful breathing techniques here!
References:
1. Souman JL, Frissen I, Sreenivasa MN, et al: Walking straight into circles. Curr Biol 19:1538-42, 2009
2. Codling EA, Plank MJ, Benhamou S: Random walk models in biology. J R Soc Interface 5:813-34, 2008
3. Marques B, Colombo G, Müller R, et al: Influence of vestibular and visual stimulation on split-belt walking. Exp Brain Res 183:457-63, 2007
4. Cohen HS: Vestibular disorders and impaired path integration along a linear trajectory. J Vestib Res 10:7-15, 2000
