Paolo Giusti Posted about 6 years ago Dan Ariely: Are we in control of our own decisions? Rationality in the most general meaning is the use of common sense, unless my english knowledge is too poor, and with this meaning it's ok that my common sense could and actually is different from another's one. But I think Dan is using "rationality" with a more subtle meaning. Think about the meaning of logic, synonym of rationality, in math.There is no doubt that has nothing to do with personal conviction. I agree that neither "rationality" nor "logic" fit perfectly with visual illusions. But the fact is that the colours are actually identical, the background is giving us the illusion that one is lighter. So what influences us are not only the foregrounds (the colours), but backgrounds as well and even more sometimes. As he said visual illusion are to be taken as metaphores. And for the rest of the talk what he says is that we are fooled by backgrounds.