Researchers gave a group of people two cups of ordinary coffee but told them one was organic.

They then asked them which tasted the best. Despite the two drinks being identical, the participants said the supposedly "organic" version was nicer.

The Swedish study concluded that labelling alone seemed to be enough to alter expectations.

It said, "An increasingly large number of products are marked with morally loaded labels such as fair-trade and organically produced -- labels associated with social or environmental responsibility that speak to our conscience.

"We show that eco-labels not only promote a willingness to pay more for the product but they also appear to enhance the perceptual experience of the product’s taste. Who needs cream and sugar when there is eco-labelling?"

Researcher Patrik Sorqvist added, "In the case of crop products,  like coffee, consumers could quite easily imagine production differences that could influence taste, such as crop spraying."

Their study builds on earlier research which found we also tend to assume that organic products are healthier and have fewer calories.

Four in five British households buy organic products, despite their premium price tag. Annual UK sales now top £1.5billion.

Organic fruit, vegetables, eggs and meats are typically, produced without the aid of pesticides, artificial fertilisers or intensive farming techniques. However, in 2009, a landmark study from the Food Standards Agency declared organic food to be no more healthy or nutritious than ordinary products.

The researchers, from the University of Gavle, published their study in the journal PLoS one.