The results could usher in a new era of “neuro-marketing” which will delve deep into the brains of consumers.
Neuroscientist Read Montague, from the Baylor College of Medicine in Houston, Texas, found the answer to the cola conundrum using a brain scanning technique called functional magnetic resonance imaging (fMRI).
The technique can identify activity in different parts of the brain in real time.
A number of volunteers were scanned as they drank either Coke or Pepsi blindly and reported which tasted best.
The scientists found that a brain region called the ventral putamen lit up most strongly when people drank their favourite cola. This area is known to be associated with seeking reward.
Just as previous tests had shown, more of the volunteers preferred Pepsi.
But when people were told what they were drinking, their preference changed - and Coke came out on top.
This time the brain area which showed most activity was the medial prefrontal cortex, a spot associated with higher thinking processes.
New Scientist magazine reported yesterday: “The results - which Montague hopes to publish soon - showed that people make decisions based on their memories or impressions of a particular soda, as well as taste.”
In the advertising world, such “brand recognition” is the Holy Grail.
Researchers hope the new approach might help them pin down what lies behind this elusive quality.
Another US expert, Clinton Kilts from Emory University in Atlanta, Georgia, believes it is all about making people identify with an object.
His own scanning tests showed that the same prefrontal brain region activated in the cola taste test lit up whenever people looked at pictures of things they loved.
Some already fear that neuromarketing could boost advertising-related diseases such as obesity.
But Joey Reiman, chief executive officer at Atlanta-based marketing consultants BrightHouse, strongly believes it could be a force for good.
“What if you could, for example, show a company that their ethical behaviour has a bigger influence on consumer preference than the colour of their packaging or current tag line?” he told New Scientist.