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To test their hypothesis that excessive or inappropriate generosity may be due to damage to a very specific part of the brain, the University of Utrecht researchers recruited three volunteers who had tiny points of damage on both sides of a part of the amygdala known as the basolateral amygdala (BLA) without any damage to another part of the amygdala known as the central-medial amygdala (CMA). They also recruited nine volunteers who had no brain damage. Then they asked the volunteers who had BLA damage to play a "one-shot trust games" with the volunteers who did not have brain damage.

In the trust game, one player is an investor and one player is a trustee. Both players receive the same amount of money. The investors can then send any amount of money they want to their trustees, and that amount of money is multiplied by three. Then the trustee can send any part of the money received, or no money at all, back to the investor. The volunteers were given real money for the game.
When volunteers who had brain damage played the role of trustee, even though they did not have to return any money at all, they typically returned about twice as much money as players who did not have this kind of brain damage. Volunteers who had damage to the BLA did this even though they said they did not expect the game to be fair.
Brain researchers have observed a pattern of behaviors associated with "easy marks" at risk of falling victim to scams.
People who have damage to the specific part of the brain associated with generosity tend to be:
- Extremely aware of their surroundings, but don't form healthy "fears" of negative influences in their environments.
- "Naturally" or "pathologically" generous, and don't learn from negative experiences after being generous with their resources, or don't care about losses enough to change their behavior.
- Impulsively generous, giving away their resources without thinking about the consequences.
Of course, just as the Apostle Paul counseled Christians to "give hysterically," in a literal interpretation of the Greek text, many people are socially conditioned to give away their conditions.
To the extent giving things away is due to brain damage, however, the good news is that lesions in the BLA tend to be the result of atherosclerosis, happening over years or even decades, giving the sufferer opportunities to learn compensatory behaviors that can keep them out of poverty.
When the brain damage is due to stroke, there is little opportunity to learn a different way of relating to others.
- Ferreira-Garcia R, Fontenelle LF, Moll J, de Oliveira-Souza R. Pathological generosity: An atypical impulse control disorder after a left subcortical stroke. Neurocase. 2013 Aug 20.
- Smith J. Brazilian stroke victim cannot stop helping others after developing pathological generosity because of changes in the brain. Daily Maily Online, http://www.dailymail.co.uk/news/article-2414951/Brazilian-stroke-victim-stop-helping-developing-pathological-generosity-changes-brain.html, accessed 11 September 2013.
- van Honk J, Eisenegger C, Terburg D, Stein DJ, Morgan B. Generous economic investments after basolateral amygdala damage. Proc Natl Acad Sci U S A. 2013 Feb 12. 110(7):2506-10. doi: 10.1073/pnas.1217316110. Epub 2013 Jan 22.
- Photo courtesy of Quazie by Flickr : www.flickr.com/photos/quazie/578252290/
- Photo courtesy of Comrade Foot by Flickr : www.flickr.com/photos/56380734@N05/8559675547
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