There was an interesting experiment where some researchers put subjects inside an MRI machine, and then fed them two samples of cola. Sometimes both drinks were anonymous, and sometimes the drink was labelled as Pepsi or Coca-Cola, while the other was anonymous but actually the same drink. When the drinks were anonymous, people seemed to like both equally, but when told what the drinks were, people tended to prefer Coca-Cola over the anonymous drunk. Even more interestingly, when people were told they were drinking Coca-Cola, extra bits of their brain lit up, specifically memory and cognitive control, which suggests that when you think you're drinking Coca-Cola, it's not just the immediate sensation of drinking the coke that affects how much you enjoy it, but also the effect of all of that marketing that makes your brain think "Mmmm, Coca-Cola is delicious!"
http://health.usnews.com/usnews/health/briefs/mentalhealth/h...