Wearing a dunce cap also prevents any change to your intelligence or wisdom; the message is "Your cap constricts briefly, then relaxes again." Shopping while wearing a dunce cap will cause the shopkeeper to add an additional 1/3 markup to the price of each item, and only give you 1/3 of the base price when selling items. This is not in addition to the penalty for being a low-level Tourist or having a visible shirt.