Playing mind games with taste
2006-01-11 15:13
Cape Town - You're mad about a cheeseburger, but queasy at the thought of fish - researchers have found this has to do with the way specific areas in the brain form associations.
Professor John O'Doherty at the California Institute of Technology in Pasadena and several colleagues, in the latest issue of the journal Neuron, give far more than mere insights into people's preferences for food and drink. Their findings have brought humankind closer to understanding the fundamental nerve mechanisms the brain uses to determine all preference behaviour.
All in the state of the mind
The researchers studied the human brain with functional magnetic resonance imaging (fMRI). The people they studied were given four different fruit juices to drink, while four different arbitrary images flashed on a screen.
The people were, without knowing it, being conditioned to associate the images with the juices. Advertisements for brand names also work like this. By studying the brain scans, the researchers saw significant reactions in the brain, indicating learned preference behaviour. The reactions occurred in the ventral midbrain and ventral striatum.
People generally prefer certain foods or drinks by learning to associate them with a predictive portrayal of the value of that particular kind of food. Sometimes these predictive associations can be linked to a trademark.
Preferences could be altered
O'Doherty said in an e-mail to Die Burger that people's preferences could be changed by combining classical conditioning with pleasant stimuli. This is why advertisements are so powerful.
He said similar learning mechanisms could make a person learn to dislike certain foods. ''The most usual way of disliking food is to associate it with disease, for example eating a type of food and then feeling nauseous. People will learn to associate the queasy feeling with the type of food,'' he told Die Burger.
He added that the ventral striatum at least would be involved in the positive and negative reaction to food. The ventral midbrain, where dopamine comes from, would be more involved in positive associations.
O'Doherty said the amygdala was also involved in positive and negative learning. He said one changed one's feelings about food all the time, and one made associations even as a child by associating a product with another pleasant event. But social factors, such as group pressure, also played a role.