In experiments where people were given Coke and Pepsi in unmarked cups and then hooked up to a brain scanner, the device clearly showed a certain number of them preferred Pepsi while tasting it.
When those people were told they where drinking Pepsi, a fraction of them, the ones who had enjoyed Coke all their lives, did something unexpected. The scanner showed their brains scrambling the pleasure signals, dampening them. They then told the experimenter afterward they had preferred Coke in the taste tests.
They lied, but in their subjective experiences of the situation, they didn’t. They really did feel like they preferred Coke after it was all over, and they altered their memories to match their emotions.
They had been branded somewhere in the past and were loyal to Coke. Even if they actually enjoyed Pepsi more, huge mental constructs prevented them from admitting it, even to themselves.