CHAPTER 12 The Design of People
Seeing iS believing iSn’T Seeing
Optical illusions provide a great example of our limitations.^14 My personal
favorite is the checkershadow illusion first developed by MIT researcher
Edward Adelson.^15 The illusion here involves deciphering the colors of
the squares marked A and B in the left image of figure 7. When asked,
participants (including you) will indicate that A is dark gray, while B
is light gray. The squares, in fact, are the same shade of gray. And this
becomes clear as day when you connect the two squares with a solid gray
rectangle as shown in the right image. But the best part of this illusion is
yet to come.If you take the gray rectangle away (look back at the left figure), it’s as
if we’re stupid again. No matter how hard we try, we see the two squares as
entirely different shades of gray.
Despite the fact that our visual system — more than thirty
different parts of the brain dedicated to helping us see — is about
the most anatomically sophisticated part of the human body, we are
predictably fooled over and over again by optical illusions like Adelson’s
checkershadow. In Predictably Irrational, Ariely wonders how often, then,14 Dan Ariely at EG ‘08 Podcast, FORA .tv.
15 Edward Adelson, Checkershadow Illusion.