The Unexpected Bitterness Tastes Better

The sensation you experience when you taste something does not depend solely on what you taste - it also depends on what you expect. It was previously shown that such an effect does not exist in case of primates, so neuroscientist Jack Nitschke and his colleagues at the University of Wisconsin wanted to check whether it exists in case of humans.

They gave a test to 30 participants. The scientists prepared five drinks containing water mixed with varying amounts of quinine or sugar and paired them with five symbols: water with a strong concentration of quinine was linked to a minus sign; water with a milder concentration got a crossed-out minus sign; simple distilled water received a zero; and water with either a mild or strong concentration of sugar got the plus sign equivalents of their negative counterparts.

The participants tasted the drinks in three trials in order to learn the associations.

The researchers then subjected them to a fMRI test while giving them another round of drinks, this time, however, mixing the signs and drinks. The fMRI test is capable of literally detecting which areas of the brain are being used when a certain task is performed. Thus, the scientists induced a certain expectation using the signs, but then they deceived the expectation giving them the wrong drink. They wanted to see whether the expectation will have any influence on how the brain will react to a specific drink.

"These data show that neural responses to taste in the primary taste cortex are modulated by expectations and not solely by the objective quality of taste," the researchers write in a paper published yesterday by Nature Neuroscience.

When the participants were shown a sign indicating a mild bitter drink, but actually they received the bitter drink, the same regions of the brain that fired when the subjects believed they were going to taste the bitterest drink still fired, but they did so less strongly. The participants also reported that the drink tasted less bitter to them. The same influence of expectation on taste perception was evident when the subjects received the sugared water.

In other words, taste does not belong 100% a property of what is being tasted, it is partly in your mind. This mirrors what is already known about the partial subjectivity of vision.