A PREFERENCE for the taste of Coca-Cola or Pepsi lies in the mind as much as on the tongue. Scientists have discovered that when people know which of the two brands they are drinking, their brains respond differently to when they taste the drinks “blind”.

The findings, the result of brain-scanning technology, show how easily cultural influences can affect perceptions that most people think are created by their senses alone. They demonstrate in stark neurological terms the way in which brand images and aggressive marketing sway choices made by the brain.

On this measure, Coca-Cola appears to be doing a better job: the study found a characteristic pattern of brain activity in volunteers who knew they were drinking Coke, but nothing comparable for those who knew their fizzy drink was Pepsi.

Samuel McClure, who led the research at Baylor College of Medicine, in Houston, Texas, said: “In this brand-cued experiment, brand knowledge for one of the drinks had a dramatic influence on expressed behavioural preferences and on measured brain responses.”

The research team set out to investigate whether brand images had a visible effect on the brain, and chose Coke and Pepsi because both products are so similar, yet provoke strong opinions in many people.

“Coca-Cola and Pepsi are nearly identical in chemical composition, yet humans routinely display a strong subjective preference for one or another,” Dr McClure said.

“This simple observation raises the important question of how cultural messages combine with content to shape our perceptions, even to the point of modifying behavioural preferences for a primary reward such as a sugared drink.”

In the study, 67 volunteers were asked whether they preferred Pepsi or Coke and then were given a blind taste test while their brains were scanned by functional magnetic resonance imaging. The technique measures activity in different regions of the brain by charting the flow of blood to particular areas.

The subjects were then scanned again, while their sips were preceded by a picture of either a Coke or Pepsi can flashed on to a screen. This produced a very different set of brain responses. When a Coke can was displayed, it activated other parts of the brain as well. A Pepsi can, however, did not have the same effect.

The results, reported today in the journal Neuron, suggest that Coke’s branding has been so successful that it stimulates a cultural preference in the brain that might sometimes override preferences based solely on taste.

“There are visual images and marketing messages that have insinuated themselves into the nervous system of humans that consume the drinks,” Dr McClure said.

“Sensory information plays only a part in determining people’s behaviour. Brand knowledge, at least in the case of Coke in our study, biases preference decisions.”

TIM HAMES: I WANT TO JOIN IDIOT DIET SODA DRINKERS ANONYMOUS

How humiliating. It is in the mind after all. I have drunk Diet Coke solidly for 16 years (apart from the very occasional foray into red wine) and felt absolutely confident that I could pick it out in any blind taste test without the slightest doubt or hint of hesitation.

Yet when put to the test I failed miserably. With total confidence, I took a large swig of each and declared, utterly self-assured, “that’s the Diet Coke”, “that’s the Diet Pepsi”.

I was completely wrong. What is worse, as I continued to glug the Diet Pepsi — a substance which I have insisted for more than a decade and a half that I do not like — it became more obvious that there is no serious difference between it and its rival.

For so many years I have been fooled by a mixture of familiarity and marketing. This is a social catastrophe.

If there were a body called IDSDA (Idiot Diet Soda Drinkers Anonymous) I would join it.

ROBIN YOUNG: I FOUND THE ODD ONE OUT, BUT I ALWAYS AVOID COLA

THE scientific way to test for discernible differences between two similar drinks is to set up triangular blind-tasting tests. These use three identical containers filled with the two liquids, two with one sample and one with the other. The taster must then identify the odd one out.

Between Coke and Pepsi, one drink was more opaque, less fizzy, smelt sharper and was more aggressive to the palate.

I found the odd one out in each of three tests, but, because I have always avoided cola, I had no means of telling which was Coke and which Pepsi.

Indeed, the last time I was asked to taste colas for The Times I got friends, neighbours and colleagues to do the tasting for me, and then quoted their remarkably contradictory opinions.

This time, it turned out that the thinner, sharper brand was Pepsi. But that does not mean that I want to taste Coke again for a long time either.

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