Seeing the world as it isn't

An earlier version of this post appeared on my Psychology Today blog on April 30, 2010.

When we look at the world around us, we feel that we are seeing it as it is. Most of the time, we are — but not because our visual system perceives the world precisely as it is. Rather, our visual system makes informed guesses about the contents of the world based on the compressed signal projected onto our eyes. And, for most practical purposes, those guesses are pretty good. Moreover, this "guessing" system work so seamlessly that we rarely notice any discrepancy between our guesses and reality. Only when we "break" the system can we reveal these default assumptions.

My 7-minute long talk at TEDxUIUC in February 2011 explains why we have to break the visual system to understand how it works. As an added bonus, I showed some terrific illusions and demos from Julian Beever, Bart Anderson, and Bill Geisler. Check it out:

Just as we can't intuit the mechanisms of vision, we lack insight into the mechanisms of memory, reasoning, and thinking. Only when forced to confront what we're missing do we realize that we've unwittingly made assumptions. We often have no idea how limited our abilities can be. The following change blindness video illustrates one such limitation:

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. 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. In fact, people who missed the change would never have known anything was amiss had we not asked them. 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.

Source cited:

Simons, D. J., & Levin, D. T. (1998). Failure to detect changes to people during a real-world interaction Psychonomic Bulletin and Review, 5, 644-649 : 10.3758/BF03208840