Sex and money: common or different brain currencies?
Is money treated in a different region of the brain than other types of reward?
How are values computed in the brain? Rewards can be as many things: the expectation when having just ordered your favorite dish; the child’s joy on Christmas Eve; the enjoyment of good music or the wonderful taste of strawberries.
But how does the brain process these many different kinds of rewards? Does it treat all types of rewards equally or does the brain distinguish between different types of rewards? Rewards can come in many different forms: sex, social recognition, food when you’re hungry, or money. But it is still an open question whether the brain processes such rewards in different ways, or whether there is a “common currency” in the brain for all types of rewards.
In a now classical study, Guillaume Sescousse and his colleagues in Lyon reported a study on how the brain reacts differently to money and sex. A group of men was scanned with functional MRI. While being tested, subjects played a game in which they sometimes reviewed a reward. The reward could be money or it could be the sight of a lightly dressed woman. So there were two types of rewards.
Here’s the twist in valuation: money is arguably an indirect reward. By contrast, sexual images can be seen as more immediately rewarding (at least for most heterosexual men).
How did the brain process these rewards?
The researchers found that there were unique activations for both sex and money, but also overlapping regions of activity. On one hand, both types of reward included a general activation of regions typically associated with reward responses (e.g., ventral striatum, anterior insula, anterior cingulate cortex, and midbrain; see red dots on the figure below). The brain thus uses some structures to respond to both types of reward.
But there were also specific activations for either erotic pictures or money. This difference was primarily made in the brain’s prefrontal cortex, specifically the orbitofrontal cortex (OfC). Here, it was found that monetary rewards engaged more anterior OfC regions, while erotic images activated more posterior OfC regions.
This could suggest that the brain also treats the two types of reward differently. These can be seen as separate activations in the figures below.
However, the crux of this paper is how one explains the difference. As noted, the researchers used two different kinds of reward, but they differ in several ways which I will try to summarize here:
Direct vs indirect
Money is indirectly rewarding because money can not be ‘consumed’ in itself. They are rewarding to the extent they could be exchanged for other things. Erotic images are in themselves directly rewarding. Not because they symbolize sex or the possibility of sex, but because they have immediate rewarding effects.
Abstraction level
Another option is to say that erotic pictures and money differ in their level of abstraction: Erotic images are concrete, while money is an abstract reward.
Time interval
A final possibility is that there are differences in the time interval: Erotic images are immediately rewarding, while the money can only be converted into real value after a while (for example, after scanning, or after a few days where you spend the money). We already know that the frontopolar regions of the brain are among the regions that are most developed in humans compared to other primates, and are linked to our unique ability to think about the future, i.e. prospective memory and planning, and through this to use complex abstractions for rewards, including money.
What it all means
The exact cause of this common currency as well as the separation between money and erotic pictures is still unclear and warrants further studies (which I am currently undertaking). The essential addition of this study is the separation between the posterior and anterior parts of the OFC in processing different kinds of rewards. By showing common and distinct regions, this study may resolve some of the ongoing debates in the decision neuroscience / neuroeconomic literature. But as always found in science, this study generates more questions than it resolves, and we can only hope that future studies can add to this knowledge.
#neuroeconomics #neuromarketing #consumerneuroscience #valuation #decisionmaking #economics #erotics #reward
