This is a guest post by Daniel Griffin, one of Greta's top student writers for Spring 2007
How well do you think you can navigate through these woods?
How about when your field of view is significantly reduced?
When external information such as sight is decreased, our ability to make our way to a goal while avoiding obstacles will understandably be impaired.But when we lose all visual information we can still make mental representations, or "mental maps" of our surroundings. Even blind individuals compare with those who can see in tasks such as recreating large scale representations of their surroundings. We depend on external cues for navigation, but the effectiveness of mental maps contributes what we consider "good" navigators. Do you ever get lost going to a restaurant that you have been to before? Much like driving a car with a GPS onboard, using a map -- mental or physical -- will help in arriving at a specific location faster than just looking out the windows. Francesca Fortenbaugh and colleagues explored the effectiveness of using mental maps in navigation by studying goal directed walking -- a procedure in which subjects are told to find their through a course to a certain target.
The study used a novel approach to look at how we employ visual information and mental mapping to quickly and efficiently walk to a goal in a 3-D world. Fortenbaugh set up a "virtual walkthrough" task where subjects were put in an empty room and given a virtual reality headset which portrayed a 3-D virtual forest. The participants could walk around the room, their movement coordinated with their visual environment in the headset as they made their way to the target. This forest contained three obstacle trees in front of a target tree with different bark. Additional trees were placed in the virtual environment outside the scope of the room so that the individual could not tell where the actual walls of the testing area were. The field of view for each participant was manipulated so that in a trial they could see 40, 20, or 10 degrees of their virtual world in the headset.
Researchers paid special attention to travel time, obstacle trees hit, and length of path taken when compared to the shortest possible route. Based on these measures the participants were divided into good or poor navigators. Not surprisingly, the better navigators were faster to both begin moving and to arrive at the target once they started walking. But more importantly to this study of effective mental mapping, performance times deteriorated fastest for poor navigators as the view got smaller. Even with nearly a 50% smaller field of view, good navigators performed at the same level as the poor navigators. The figure below shows how the poor navigators (blue) take increasingly longer than the good navigators (red) as the field of view gets smaller.
It can be assumed that the two groups of navigators used both external visual information and internal mental representations but did not rely on them equally. Both groups of target finders walked at approximately the same speed but the good navigators hit fewer obstacle trees and were redirected away from the walls of the testing area significantly less, showing that the difference between the times of the two groups was due to walking strategy and not pace or recklessness.
Here's a movie of a poor navigator's path through the forest:
Now compare that to a good navigator:
That's some difference! The fact that the good navigators completed the trip in the same time with a much smaller field of view shows that they compensated for loss of vision with an effective mental map of the forest. The difference between the two cannot be determined from this indirect method of studying internal mapping strategies, but the data do suggest that integrating visual information into a mental representation gives a better sense of where you are and where you need to go in a goal directed walking task. Researchers did not to draw any firm conclusion about why the good navigators may possess better mental mapping abilities, but they suggested that this effect may reflect the manner in which good navigators store information in their short term memory, or perhaps have more effective searching patterns. Good navigators did not differ from the poor navigators on gender, age, height, or gait. There is no mention of physical coordination however, which could be an interesting tie-in with the goal directed walking task.
Navigation using both external visual information and mental mapping is the standard for most people. But some of us come equipped to create better internal representations of our surroundings and get where we want to go faster. Which one of these two subjects do you think you would be? If you're more like the first movie, then maybe you should look into getting a GPS.
Fortenbaugh, F.C., Hicks, J.C., Hao, L., & Turano, K.A., High speed navigators: Using more than meets the eye. Journal of Vision, 6, 2006, p. 565-579.
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This may explain the large variation in the ability of office workers to navigate large cubicle warrens.
Some layouts seem diabolical, as if they were intended to confuse people. Others clearly were intended to make it easy to navigate them.
Cubicle warrens may -- I'm said to say -- be a more appropriate test of mental mapping than a forest full of trees.
interesting that there's no variance for sex. i thought men were better at 3d visualization? that would seem to be a helpful skill in an exercise like this.
It's not really that interesting or surprising that there aren't sex differences since this task allows a multitude of different navigation strategies. Men are just slightly better at some strategies.
I wonder if this variation persists if you put back other stimula such as feel and sound? You can hear the difference between having a wall next to you and having open space in the echos of your footsteps or other ambient noise, and certain highly trained individuals can actually feel objects near to them, presumably from reflected heat and change of airflow, and can thus trace surfaces without touching them at fairly high speeds. So perhaps the question is really how fast people offload navigation onto other senses? If you offload very quickly, then perhaps your are a poorer navigator when given just a narrow field of view than someone who offloads slowly.
I think those who navigate better just have bat radar genetics. Maybe Dracula spread his genes around more than we realize. (just kidding :-)).
Actually though, I am surprised that there was no difference shown for the sexes. It seems to me that men are pretty much ALWAYS lost and refuse to ask for directions, while a woman is pretty much always lost too, but she has no problem with asking for directions.
Personally, if I have no specific appointment to meet, I love being lost. It's amazing the things you discover. It's sort of like being Magellan on the high sease---you never know exactly where you will land or what you will find, and the natives are usually friendly.
Nice review, thanks. Out of interest, how was the arrangement of 'trees' decided? If random/pseudorandom, was there any allowance made for any difference there might be not in path length, but in number of turns necessary over that path (i.e. complexity of path)? In the first video for example, the subject would have to correct his course twice to pass around the last two of three trees blocking his path, whereas in the second, only one correction would have to be made. Just a thought...
I think that the conclusion that mental mapping is used is fairly uncontroversial. What is more interesting (only my opinion of course) is the manner in which these mental maps are represented neurally. Would they be human analogues of the euclidean representations theorised by many conducting rat studies (place cells, etc), or otherwise (a question central to my own work)? Was wondering if you had any thoughts on this?
i fail to see how navigating a 3d space isn't affected by one's 3d spatialization ability, especially when input is attenuated.
Please could someone do some research to explore if there is a link between poor visual field and memory.