Nature vs. Nurture
Is the pious loved by the gods because it is pious, or is it pious because it is loved by the gods? Socrates, Euthyphro
I recently skimmed Barbara Oakley’s Evil Genes where she explores the relationship between genes and behaviour. She presents some interesting research in genetics, molecular biology, and psychology while also drawing on her personal experiences to find explanations for why antisocial people behave the way they do.
There’s a broad consensus among researchers that adulthood personality is largely a result of two factors.
- Genetic predispositions.
- Early childhood experiences that shape the brain (quite literally) and determine the mental model of the world that the child acquires.
For simplicity, we can think of the first one as nature and the second one as nurture, though they’re not so black and white. Why not? Epigenetics.
It’s the study of how certain genes turn on or off in response to environmental stimuli. Essentially, your body can interpret a gene differently depending on your external environment. These epigenetic expressions seem to be essential to the development of neurological processes.
Oakley presents a case of abused boys with a genetic predisposition for lower levels of Monoamine oxidase A (an enzyme that breaks down neurotransmitters in the brain) who are more prone to violence or criminal behaviour than other abused boys. However, when these children are raised in a normal environment, the gene doesn’t appear to affect their behaviour.
She goes on to discuss the genetic origins of antisocial behaviour using a study of highly psychopathic twins that found a heritability of 81%. The remaining 19% of influence appeared to be due to differences in how the two twins were raised.
This leads her to suggest that some children are born with a marked tendency towards “evil”. For example, a four-year-old with antisocial tendencies is highly likely to engage in criminal behaviour when they grow up and there are few, if any, professional interventions that can prevent this.
HPA Axis
Hypothalamic-pituitary-adrenal axis is a neuroendocrine system inside body that regulates many neurological and physical processes, most notably reactions to stress. There’s substantial scientific evidence that dysregulation of the HPA axis is responsible for the vast majority of functional mental and physical disorders.
Exposure to extreme or prolonged prenatal or early-life stress can lead to a hyper-reactive HPA axis. A study found that rats exposed to prenatal stress had elevated basal levels of corticosterone (a stress hormone). Moreover, it took longer for their stress response to return to normal following exposure to stressors.
There’s also evidence that children of mothers who suffer from depression during pregnancy have higher cortisol (another stress marker) levels than other children.
Another study found that rats subjected to extreme stress by prolonged separations from their mothers during the early weeks of their life showed heightened stress responses as adults. On the other hand, moderate early-life stress was linked to stress resilience in adult rats.
It seems that there’s a critical period in early life during which the HPA axis is calibrated based on how much stress an individual experiences during that time. Consequently, children raised in highly stressful environments tend to grow up to become stress-sensitive adults.
Free Will
If we’re all just products of genetics and learned behaviour, how can there be such a thing as human agency? If every action one takes is determined by factors outside their control, how can one be held responsible?
Schopenhauer, in his 1838 essay On the Freedom of the Will, famously wrote:
Man can do what he wills, but he cannot will what he wills.
While we are free to act according to our desires and intentions, we do not have control over how those desires and intentions are determined in the first place. This is the compatibilist view that tries to reconcile determinism (lack of absolute free will) with the existence of human freedom.