University of Tokyo researchers have developed a virtual reality system that can alter taste perceptions. Subjects are hooked up the system and given a plain, flavorless cookie. They are then shown an image of a specific kind of cookie, say oatmeal raisin, and are exposed to the corresponding scent. They are asked to eat the cookie, and say what kind of cookie they are eating. The system has been able to fool people into thinking they are eating an oatmeal raisin cookie.
The system, called Meta Cookie, can't fool people regarding texture though. The system failed to convince subjects that they were eating a cookie when they were being served pudding.
Needless to say, dieters will rejoice if a system can fool them into thinking they're eating a steak when it's a stalk of celery.