People, plonk and placebos
The 'placebo effect' in medicine is a well documented phenomenon whereby the perception of effectiveness influences the actual physical experience. Jeremy Bullmore explains how branding works in a similar way.
Put the same red wine into two identical bottles. Then apply two different labels. The first label, on Bottle A, looks like this:
The second label, on Bottle B, looks like this:
Then ask a thousand experienced wine drinkers to taste each wine, conscientiously rotating the order in which the wines are sampled: 50 per cent starting with a taste of Bottle A and 50 per cent starting with a taste of Bottle B. Then invite them, without conferring, to declare their preference.