Archive for November, 2010

Is Giving Genetically Determined?

Is our inclination to charity a function of our genes?  Do we donate to help others based on our brain neurochemistry?  Scientists at the University of Bonn, Germany seem to think so.  They studied the degree of giving to help a poor child after the research participant had undergone a demanding computer task for which they were paid.  Those who had a specific variant of a certain gene gave more money to the charity than those with a different variant of the gene.  Therefore, the researchers concluded that altruism (in this case, donating money without any return benefit) was at least partially determined by genetics.

Well, that sounds good if you accept the basic ideas on modern evolutionary psychology (or “social neuroscience” as some have taken to calling this field of study) which assume that all our behaviors are determined (at least in part) by our biochemical make-up. But what does this paper really show?  If you only read the summary on a news site such as Medical News Today (http://www.medicalnewstoday.com), the data sound very convincing.  But a close look at the actual paper suggests there are flaws in the conclusions.  So what’s really happening?

The gene under consideration codes for an enzyme known as catechol-O-methyl -transferase (or COMT for short).  This enzyme is found in the brain and other tissues and is involved in the deactivation of the neurotransmitters dopamine and norepinephrine. The neurotransmitters interact with a part of the brain known as the prefrontal cortex, which helps regulate personality, behavior inhibition, and emotion, among other things.  Low brain levels of dopamine have been associated with depression, schizophrenia, and other behavioral issues.  Dopamine is considered a “reward” or “pleasure” neuro-transmitter, with increased levels associated with enhancement of psychological well-being.

There are two major forms of the enzyme: a “long” form found in the brain and a shorter form found in other tissues.  In addition, each form has structural variants that affect the amount of deactivation of dopamine produced by that variant.  The study involved analysis of DNA obtained from a mouth swab, looking specifically for genes associated with the COMT variants.  The variant with two valine substitutions (Val/Val) has the highest level of dopamine inactivation, a one-valine substitution (Val/Met) has an intermediate degree of inactivation and the variant containing two methionines (Met/Met) has the lowest amount of dopamine inactivation.  So, the assumption is that people with the Val/Val variant will have the lowest amount of dopamine available to interact with the prefrontal cortex while those with the Met/Met variant will have a higher level of dopamine; the Val/Met variant should have intermediate levels of dopamine influencing the prefrontal cortex and behavior.

The data reported show that people with the two COMT variants leading to lower amounts of dopamine donated significantly more money than those than those with the Met/Met variant which should give rise to higher amounts of dopamine in the brain.  The researchers concluded that the Val/Val and Val/Met variants could be associated with higher levels of altruism.  However, there are a number of flaws in the study that could lead to different conclusions.  Let’s take a look at some of these flaws.

COMT is not the only enzyme involved with the breakdown of dopamine and similar neurotransmitters.  The enzyme monoamine oxidase (MAO) is at least as significant (and possibly more so) that COMT in regulation of dopamine activity.  MAO genes were not assessed in this study, but the contribution of this enzyme cannot be ruled out.

The data lump Val/Val and Val Met genes together in some of the information relating COMT contributions to altruistic behavior.  This combining of gene types does not allow us to assess realistically any influence of dopamine metabolism to altruism.  When the data split out the Val/Val and Val/Met genes separately, subjects with the Val/Met variant (representing an intermediate level of dopamine inactivation) contributed more to charity than the Val/Val or Met/Met individuals.  Therefore, no valid conclusions can be drawn relating the supposed level of dopamine in the brain to altruistic behavior.  In addition, the genes were analyzed from buccal tissue (not brain tissue).  COMT from brain has a different structure than COMT from extra-brain tissues and quite possibly has different kinetics properties (not discussed in this paper).

What can we conclude from all this?  Consider all the possibilities to explain the data.   Other enzymes that would influence dopamine and norepinephrine content in the brain were not explored.  No consideration was given to the possibility that the giving of money by the (presumed) low-dopamine group stimulated the release of more dopamine into the brain, providing a reward reinforcement for the chosen behavior.

But there could be an up-side to this study.  When asked for money (church collection plate, Salvation Army bell-ringer, “homeless” person on the street corner with a sign), just respond that you are a Met/Met COMT variant and are genetically predisposed not to  give.  After all, it’s not your fault that you’re cheap.