Seeing the world as it isn't

When we look at the world around us, we feel that we are seeing it completely and accurately. With perception, we assume that the world is WYSIWYG (what you see is what you get), but that sense is illusory. Most of the time, we do see the world accurately, but we do so only because our visual system makes informed guesses about the contents of the world based on the compressed signal projected onto our eyes. These shortcuts, rules-of-thumb, and heuristics are built into the way we see, and they work so seamlessly that we rarely notice that we're using them at all. Only when we "break" the system can we reveal these default assumptions.

This change blindness video illustrates one example of this approach:

When Dan Levin and I conducted that person-change study, we found that about 50% of people didn't notice they were talking to a different person (see Simons & Levin, 1998). That sort of person-change rarely if ever happens in the world. You might assume, without doing the study, that people actually keep track of all of the details of the people they interact with. Only by making a change can you reveal the extent of their change blindness. This effect reveals what Chris Chabris and I call the "Illusion of Memory" -- we think we remember far more than we actually do.

This sort of cognitive, everyday illusion is akin to a visual illusion. When you view a visual illusion, you are seeing the world as it isn't -- the illusion capitalizes on one of the shortcuts your brain takes when processing visual information, with the result that you see the world the way you assume it to be rather than the way it actually is. With cognitive illusions like change blindness, we think we see and remember far more than we actually do because we are unaware of the shortcuts our brain takes when representing the world. For the most part, we simply assume the world to be unchanging, and typically we're right. We just don't realize we're making that assumption.