Coveting May Be Hardwired In Brain
Now a team from INSERM in Paris has shown that this tendency is not just psychological, but due to specific brain mechanisms that are essential for what has long been known as "mimetic desire", a characteristic first described by French philosopher René Girard in the 1960s when he began to write about desires and proposed that we borrow our desires from others, and this explains much of human behavior.
Co-author Mathias Pessiglione and colleagues write about their study of how they unravelled mimetic desires in the brain in the 23 May online issue of The Journal of Neuroscience.
The idea of mimetic desire is that we value objects not only in terms of their intrinsic qualities, such as how useful they are, what they do, and what they look like, but also in terms of how much they are desired by others. It also suggests mimetic desire is contagious, and spreads quickly to others, such that the desirability of an object increases the more people are interested in it.
In many respects the trait is important for human survival. For example, eating the food other people eat is a simple way to avoid being poisoned.
But the researchers suggest this adaptation breaks down when there is a short supply of desired objects.
For their study Pessiglione and colleagues studied the behavior and brain activity of 116 adults aged 18 to 39 years.
While participants underwent MRI brain scans they watched dozens of short videos showing objects like clothing, food, accessories, in different contexts. Some contexts were neutral, where the objects were just shown on their own, and in other contexts the objects appeared to be desired in some way, or as the researchers described them "as the goals of another agent's action". For instance, a piece of candy would appear in one context just "neglected" on a surface, and in another context at another time, a hand is reaching toward the candy, as if to grab it.
After observing each scenario the participants gave the object in question a "desirability score" between 1 and 10.
The results showed objects in contexts where they appeared to be "desired" by others, scored higher on desirability than objects where no interest was being shown in them. For instance, the candy that was about to be grabbed scored higher than the candy shown on its own.
When they studied the brain scans, the researchers found two areas of the brain, whose activity is already known, became active as participants made their selections.
One is an area called the mirror neuron system (MNS), which becomes active when "an individual makes a movement or sees someone else perform it. This helps to understand the actions of others," said Pessiglione. The other is the brain valuation system (BVS) which is involved with evaluating the worth of objects.
But Pessiglione and colleagues also found a third phenomenon: the two systems are linked. When a participant observed an item as an object of someone's desire (such as about to be grabbed or purchased), the mirror system activated the valuation system, effectively placing a higher value on the object.
"Crucially, the induction of mimetic desires through action observation involved the modulation of BVS activity through MNS activity," they write, adding that, "Furthermore, MNS-BVS effective connectivity predicted individual susceptibility toward mimetic desires", or as Pessiglione explained:
"The act of observing an individual wishing to purchase an object increases one's desire for this object."
He and colleagues conclude:
"We therefore suggest that MNS-BVS interaction represents a fundamental mechanism explaining how nonverbal behavior propagates desires without the need for explicit, intentional communication."
Pessiglione went on to say that dysfunction in these areas may explain some problems of sociability, for example autistic children often appear not to place the same value on objects or seem interested in different things to non-autistic children.
"But this remains to be demonstrated," he said.
Written by Catharine Paddock PhD