See if this sounds familiar. You and three other friends have gone to a nice restaurant for dinner. The waiter passes the menus around and you are eyeing the pork chops in some kind of fancy glazed sauce. The lamb chops sound nice too, but your preference is clearly for the pork chops. The waiter is going around the table taking orders. Your good friend who is ordering just before you goes for the pork chops. You hear that and decide to order the lamb chops because you don’t want to get the same thing your friend got. Sound familiar? Why does this happen? Why didn’t you choose your favorite dish? Do other people act this way? That’s what Dan Ariely and Jonathan Levav asked themselves. As researchers of consumer behavior, they are well qualified to search for the answer.