The Nature-Nurture Debate and Behavioral Genetics

As my readers surely know, the nature-nurture debate in science continues unabated. Especially in psychiatry. When it comes to certain repetitive emotional reactions shown by a given individual, many in the field prefer to believe that the individual was just born that way. The truth, as described in Robert Sopolsky’s excellent book Behave, is that we have hundreds or even thousands of genes that make certain behaviors either a little more or a little less likely. No complex human behavior is determined entirely by a gene or group of genes. We are also strongly programmed to tend to react in certain ways to the behavior of our kin group, although we can still make the difficult choice not to once we reach a certain age.

Genetic and Environmental Factors in Emotional Reactions

There is without a doubt a strong genetic component to true brain diseases like Major Depressive Disorder or schizophrenia, but the situation for other emotional reaction patterns is that they, in my opinion, are far more affected by the family environment than by any specific genes.

Some studies sure do point in this direction. For example, in a recent study published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, Judith Morgan, Ph.D., recruited 49 children aged six to eight without a history of psychiatric illness. Half the kids’ mothers had a history of clinical depression, and half had no psychiatric history. To measure reward-related brain activity, children played a video game in which they guessed which of two doors contained a hidden token while they underwent functional magnetic resonance imaging (fMRI).

The Influence of Maternal Depression on Children’s Reward-Related Brain Activity

Depression may disrupt parents’ capacity for emotional socialization, a process by which kids learn from their parents’ reactions to their emotional responses. Positive socialization responses include acknowledgment, imitation, and elaboration, whereas negative or emotionally dampening parental responses may be dismissive, invalidating, or punitive.

“Nature and nurture are not enemies; they are partners in shaping human behavior.” – Robert Plomin

Mothers participating in the study completed an extensive questionnaire designed to measure parental emotional socialization by presenting a dozen situational vignettes of children’s displays of positive emotions and collecting parents’ reactions to them. Children with a maternal history of depression were more likely to have reduced reward-related activity in a part of their brains that handles this, but only if their mothers reported less enthusiastic and more dampening responses to their children’s positive emotions, the researchers found.

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