For example, if I appear to have very different preferences at different points in time (e.g. I prefer to hold a red apple on odd hours and a green apple on even hours), you can extract money from me, and that seems “irrational” to us.
This is everyday rational behaviour, disguised by the details of the example. Sometimes I want something to eat and sometimes I do not. Are the managers of restaurants and food shops money-pumping me by selling me sustenance over and over? If I take the train to work in the morning, and take the train home in the evening, is the train operator money-pumping me? If I have a bed for when I prefer to sleep, and chairs for when I prefer to wake, is the furniture store money-pumping me? No, I am gaining from each purchase and have no cause to regret any of them.
Another classic example: someone who mostly has consistent preferences, which can be simply described by a utility function, but also prefers apples to bananas, bananas to oranges, and oranges to apples.
At the moment there are cherries, plums, and oranges in my fruit bowl. (There are! I am not making this up!.) Which I prefer to choose from them, when I do, is negatively correlated with my most recent choices. So which of them do I prefer? The ontology of the question is wrong. My preference function, if there is one, is not over “cherries”, “plums”, “oranges”, or any other types of fruit. In the longer term, almost every fruit I see in the shops will rotate through my fruit bowl on occasion.
If someone’s preferences look incoherent to me, maybe I am mistaken about what sorts of things their preferences are over. Behaviour reveals nothing, without the motive.
This is everyday rational behaviour, disguised by the details of the example. Sometimes I want something to eat and sometimes I do not. Are the managers of restaurants and food shops money-pumping me by selling me sustenance over and over? If I take the train to work in the morning, and take the train home in the evening, is the train operator money-pumping me? If I have a bed for when I prefer to sleep, and chairs for when I prefer to wake, is the furniture store money-pumping me? No, I am gaining from each purchase and have no cause to regret any of them.
At the moment there are cherries, plums, and oranges in my fruit bowl. (There are! I am not making this up!.) Which I prefer to choose from them, when I do, is negatively correlated with my most recent choices. So which of them do I prefer? The ontology of the question is wrong. My preference function, if there is one, is not over “cherries”, “plums”, “oranges”, or any other types of fruit. In the longer term, almost every fruit I see in the shops will rotate through my fruit bowl on occasion.
If someone’s preferences look incoherent to me, maybe I am mistaken about what sorts of things their preferences are over. Behaviour reveals nothing, without the motive.