Whether people prefer Coke or Pepsi is not just a matter of taste. Knowing which one they are drinking apparently influences their preference, new findings suggest.

Moreover, knowing the brand name of the beverage appears to activate different types of brain activity than when people taste the soda without knowing what it is, the researchers found, suggesting that branding affects the brain.

“Cultural influences on our behavioral preferences for food and drink are now intertwined with the biological expediency,” Dr. P. Read Montague of Baylor College of Medicine in Houston, Texas and colleagues note in the journal Neuron.

Even though Coke and Pepsi are “nearly identical” chemically and physically, many people strongly prefer one or the other, the team points out.

To investigate what determines that preference, they asked 67 people to drink unlabeled and labeled cups of either soda, and scanned their brains during the taste tests.

During one test, participants chose between two unmarked cups, one containing Coke and the other Pepsi. Nearly equal numbers of people said they preferred either Coke or Pepsi, or had no preference.

During another test, both cups contained the same drink, but only one had a label indicating which beverage it contained.

In this situation, the subjects said they strongly preferred the labeled cup when both contained Coke. Their brain scans also showed different types of activity than when they sipped Coke without first seeing the brand.

This bias towards the labeled cup did not occur when both contained Pepsi, and the brain scan pattern did not occur.

This suggests that two different brain systems - one based on taste buds, another based on cultural conditioning - help determine our preferences for food and drink, the investigators conclude.

SOURCE: Neuron, October 14, 2004.