Ignoring Changes and Preserving the Illusion of a Stable World

If you move with the same speed alongside something that moves, you naturally see that thing at rest. But what if everything would move away from you or if all the objects would start growing or shrinking? You wouldn't expect not to notice such a change. However, a virtual reality experiment conducted at Oxford proved just that!

In an old Star Trek episode the crew found themselves in the unsettling situation that the Enterprise ship grew relative to their own size. Their dilemma was: Are we shrinking or is the ship growing? However, as absurd as it might sound, in reality they wouldn't have observed any change occurring! At least not until the change reached dramatic sizes.

Researchers are stupefied that humans can be "blind" to changes like this. We are able to estimate distances and sizes because we have two eyes. Each eye sees the world from a somewhat different perspective. The brain can analyze the difference between the two pictures and extract information such as 'object A is further away than object B'.

A different method used by the brain to determine distances and sizes is to compare two successive pictures. For example when you walk a few steps in a certain direction the image you see changes. The brain knows you have walked a few steps and infers from the differences between the two images information such as the distance to a building or its height. When you walk a few steps the image of a building that is further away changes to a smaller degree than the image of a building that is closer.

However, Dr. Andrew Glennerster and colleagues have shown that people experiencing the virtual-reality display failed to notice when the virtual scene around them quadrupled in size as they walked around, and, as a result, they made gross errors in judging the size of objects.

In other words, in this virtual reality experiment people were more inclined, unconsciously of course, to assume that the distance between their eyes increased or that the length of their own footsteps increased than to assume that the landscape around them had changed. Thus, the capacity of adapting to a changing environment is so deep-rooted in our brains that, in order to fit in, our unconscious mind has no problem in assuming our heads had miraculously quadrupled in size.

More broadly, these findings mark a significant shift in the debate about the way in which the brain forms a stable representation of the world. Other studies have already shown for example that we estimate a distance walked based on the amount of variety seen in the exterior and not on more objective factors such as the number of footsteps we are making - a tortuous country road is perceived longer than a city street in straight line, although in reality they have the same distance. Similarly, more time seems to pass when a lot of events take place. Our image of the world is created mostly from relative qualities - things like 'how is this compared to that' - rather than from objective properties such as counting stuff.

Note: We're also doing the opposite - having the illusion of motion when nothing is actually moving.