Most of us love a piece of chocolate every now and then – but not everyone likes the same type of chocolate. Some prefer milk chocolate, while others love dark, white, or even ruby chocolate – not to talk about the myriads of different flavors ranging from classics like hazelnuts or almonds to more unusual fares such as chili peppers or bacon.
New research from Germany now shows that all chocolate isn’t created equal when it comes to your brain – it depends a lot on your chocolate preferences. The research team from Heinrich-Heine-University in Düsseldorf, Germany, used a technique called EEG (electroencephalography) to measure what happens in the brain if we receive chocolate as a reward for performing a task (Peterburs et al., 2019). EEG is based on the principle that our nerve cells use electricity to communicate with each other. Thus, if we use a specific part of the brain to solve a specific task, there is a measureable change in the electric activity in this brain area. EEG uses a cap equipped with dozens of little electrodes to measure changes in electric activity on the head that are caused by brain activity. Since these changes are very small, an elaborate amplifier needs to be used to measure them. By repeating a task over and over again and statistically combining the results, researchers can identify characteristic brain waves related to specific cognitive functions like attention of evaluation.
Dr. Peterburs and her co-workers recorded EEG signals from participants’ scalps while they performed a simple choice task. They were shown three orange rectangles that represented doors on a computer screen and had to choose one of them to be opened. After the participants had chosen a door, it was revealed what they had won: a bar of white chocolate or milk chocolate, or edible wafer paper. They were told that they would receive the product at the end of the experimental session. Of note, the participants were recruited so that about half of them loved white chocolate more than milk chocolate and vice versa. Nobody liked edible wafer paper better than chocolate.
When looking at the brain waves elicited by the task, the researchers noticed a curious type-of-chocolate effect. Early brain waves related to attention towards a stimulus differentiated between chocolate and edible wafer paper, but not between the types of chocolates. However, later brain waves related to more conscious evaluation of task performance clearly differentiated between the two types of chocolate, with a stronger response for the preferred type of chocolate.
Thus, the researchers could show how important individual preferences are when it comes to what we perceive as rewarding. For one person, white chocolate might elicit a huge brain response, while for others white chocolate might not do much, whereas milk chocolate gets the nerve cells firing. This study adds to a growing body of literature in Psychology showing how important individual preferences are when it comes to how we behave. Understanding the role of such individual preferences might be crucial in order to develop better treatments for disorders involving the brain’s reward system, such as gambling, addiction or substance abuse.
Peterburs J, Sannemann L, Bellebaum C. (2019). Subjective preferences differentially modulate the processing of rewards gained by own vs. observed choices. Neuropsychologia, 132, 107139.