Learning about behavioural genetics through Robert Plomin’s book Blueprint (1) has transformed my thinking about psychology and the brain.
The fact that most psychological factors show between 30-50% heritability – with no factors at all showing a lack of heritability – has shown that our genetic blueprint plays a major role in shaping our personalities, cognitive abilities and risk or resilience to psychopathology. A misconception I previously had was what was actually meant by heritability. For example, weight has been found to have a heritability of 70%. This does not mean that for any given person 70% of their weight is determined by genetics. Rather, the individual differences in weight between individuals in a particular population (mostly Western populations) at a particular time (in the last few decades) are governed by genetics. This also does not mean that we are slaves to our genetics; heritability describes what is but not does not say anything about what could be.
In both psychology research and everyday thinking, the environment is heralded as the main driver in shaping who we are. For example, in a podcast I was listening to this morning, the hosts were talking about how men who learned wrestling when they were younger had more ‘toughness’ when fighting in mixed martial arts (MMA) tournaments compared to other men who did not. They attribute this to the taxing and gruelling nature of wrestling in shaping their approach to fighting in the current day. But it may be that their ‘tough’ personalities attracted them to wrestling when they were young, and it’s those same personality traits that make them unrelenting in the ring.
This is related to another main point in Plomin’s Blueprint that I was not expecting: measures of the environment show genetic influence. Rather than a person being a passive sponge to experiences, people amplify the aspects of the environment that are aligned with their genetic blueprint and diminish parts that are not. Tough people are attracted to tough sports, more so than tough sports shaping someone to be tough.
This is my understanding of it: we are all born with a genetic blueprint which defines aspects such as our temperament, preferences and character. This blueprint is translated to the brain to execute this template. We are then placed in environments which give myriad ways to fulfil our preferences in line with our temperament and character. In different environments this could look different depending on the resources available and it could be executed to varying degrees.
It is also important to note that building our environment would only be possible for events which are controllable. Uncontrollable events – such as an unexpected death of a family member – would also have a profound impact on us, so we cannot just rule them out. The point is that, in terms of trying to change who we are, we can only focus on our genetics and experiences which are controllable. This is relevant to designing interventions for behaviour change or attenuating risk for psychopathology.
There has been a big drive to personalise medicine to improve outcomes. If we know the genetic pulls for people, we can use this to design interventions and engineer the environment specific to the person to maximise chances of success. Now that it is easier to collect and analyse genetic data in large scale studies – such as those part of CLOSER (2) – perhaps this reality is closer than we realise.