> If offered a Snickers, a Milky Way and an Almond Joy, participants would always choose the Snickers. But if they were offered 20 candy bars, including a Snickers, the choice became less clear. They would sometimes pick something other than the Snickers, even though it was still their favorite.
Just because something is your favorite doesn't mean it's rational to always choose it every time. Hot wings are my favorite food, but I don't eat them three meals a day to the exclusion of everything else. If there's a selection of 20 candy bars, possibly including ones you haven't tried before, I don't think it's irrational to try a new one since that might become a favorite. Even if it's one you already know, maybe you're just in the mood for coconut instead of peanuts at the moment. This seems like a poor way to measure irrationality.