There's a nuance here about the definition of "irrational". "Rational" often describes higher-level decision making. Here it is used to in reference simply to

There's a nuance here about the definition of "irrational". "Rational" often describes higher-level decision making. Here it is used to in reference simply to outcomes. If my underlying emotional circuitry rewards me with more units of pleasure for doing x and "experiencing pleasure" is a core motivation then it's a rational decision to do x. Now - the outcome might be "irrational" when viewed as a whole but it doesn't make sense that way unless there's another external goal. Eating chocolates doesn't have any goal other than pleasure so the Lindt/Hersheys example is rational either way. It's quite common to use these kind of analyses to imply people are stupid or irrational or both in terms of many kinds of choices but it doesn't hold water unless you own up to the implied external goal you are covertly slipping in to the discussion.