I will tell you a little bit about irrational behavior, and I want to start by giving you some examples of visual illusion as a metaphor for rationality. So think about these two tables. And you must have seen this illusion. If I asked you what’s longer, the vertical line on the table on the left, or the horizontal line on the table on the right, which one seems longer? Can anybody see anything but the left one being longer? No, right? It’s impossible. But the nice thing about visual illusion is we can easily demonstrate mistakes. So I can put some lines on; it doesn’t help. I can animate the lines. And to the extent you believe I didn’t shrink the lines, which I didn’t, I’ve proven to you that your eyes were deceiving you. Now, the interesting thing about this is when I take the lines away, it’s as if you haven’t learned anything in the last minute.

https://www.ted.com/talks/dan_ariely_are_we_in_control_of_our_own_decisions