Researchers found that diners are more likely order a sweet if they can actually see it rather than choosing from pictures or a menu description.

Experts said the new study debunked most behavioural theories that assumed the form of the menu presentation did not matter to consumers.

Scientists from the California Institute of Technology found that the value of consumer goods depended how they were presented.

The study, published in the American Economic Review, concluded that diners would be willing to pay, on average, 50 per cent more for items they could reach out and touch.

"Even if you don't touch the item the fact that it is physically present seems to be enough,” said Prof Antonio Rangel, who led the study.

“This … response is more likely to be deployed when making contact with the stimulus is a possibility."

Prof Rangel, from the university’s neuroscience and economics department, said his team wanted to prove whether it mattered if restaurants listed the name of the dessert, showed a picture, or brought a “cart” around”.

He said they also wanted to see whether a consumer was willing to pay more for a physical product to be shown to them.

In their study, the team presented foods to hungry subjects in three different forms including in a text-only format, a high-resolution photograph and in a tray placed in front of the subjects before measuring “their willingness to pay for the food”.

They found there was no difference between the values subjects put on the food depicted in the text and in the picture.

But bids on food on the tray were on average 50 per cent higher than the other two “bids”.

To ensure subjects were not influenced by the smell of a product the team also tested subjects with other “goods”, which resulted in the same results.

"We knew then that whatever is driving this effect is a more general response,” Prof Rangel said.