Perception Bias

Posted: August 4, 2008 in 2006, Articles

Tweaking the Real World
By John Bohannon
ScienceNOW Daily News
22 February 2006

Would you notice if the room around you gradually shrank to a quarter of its size? Perhaps not, according to a virtual reality experiment that suggests that we ignore what we see if it clashes with our assumptions about the everyday world.

When you think about the kind of calculations that are needed to judge the relative scale of things, it’s amazing that looking around a room feels so effortless. At a glance, we can accurately judge the size of lamps and chairs no matter where they are. Such calculations are hard work even for a supercomputer, so our brains must be taking shortcuts. According to one theory, we gather only small amounts of visual data and base most of our perceived reality on prior assumptions. For example, we accurately size up a table as we approach it, but then assume it remains the same size thereafter.

Picture of virtual room
Too weird.
People unconsciously ignored their environment when a virtual room’s size gradually expanded or shrank.
Credit: Stuart Gilson / Oxford University

To test just how deep our grasp of reality goes, neuroscientist Andrew Glennerster and colleagues at the University of Oxford in the United Kingdom created a virtual reality world befitting Alice in Wonderland. By wearing a closed helmet with motion sensors and internal movie screens, people ambled through a room and viewed a red box floating in midair. Subjects then walked to the other side of the room to an equally sized box and were asked to guess how big it was relative to the first. But on the way over, the researchers caused the walls of the virtual room to either balloon or shrink by a factor of 4. They then asked people to judge the sizes of the boxes relative to each other.

Because people didn’t notice that the room was changing size, they made wildly inaccurate judgments about the relative sizes of the boxes, the team reports 21 February in Current Biology. Glennerster says this reveals that our brains are so hardwired with assumptions about the world–for example, that rooms do not change size as you move through them–that we completely ignore what we actually see. On the practical end, the study may help software designers create more compelling virtual realities.

The findings are “very surprising,” says John Porrill, a neuroscientist at the University of Sheffield in the United Kingdom, who experienced the virtual room for himself. But he cautions that the results “may say more about virtual reality than they do about our ordinary perception of reality” because of the lack of real-world details such as seeing one’s own feet on the ground.

Related sites

  • The Oxford Virtual Reality Research Group
  • The science of illusion
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