genes, environment and behaviour

There was considerable kerfuffle on Twitter last week following a blog post by David Didau entitled ‘What causes behaviour?’  The ensuing discussion resulted in a series of five further posts from David culminating in an explanation of why his views weren’t racist. I think David created problems for himself through lack of clarity about gene-environment interactions and through ambiguous wording. Here’s my two-pennyworth.


Genes are regions of DNA that hold information about (mainly) protein production. As far as we know, that’s all they do. The process of using this information to produce proteins is referred to as genetic expression.


The context in which genes are expressed. Before birth, the immediate environment in which human genes are expressed is limited, and is largely a chemical and biological one. After birth, the environment gets more complex as Urie Bronfenbrenner demonstrated.  Remote environmental effects can have a significant impact on immediate ones. Whether a mother smokes or drinks is influenced by genetic and social factors, and the health of both parents is often affected by factors beyond their control.


Epigenetic factors are environmental factors that can directly change the expression of genes; in some cases they can be effectively ‘switched’ on or off.   Some epigenetic changes can be inherited.


Behaviour is a term that’s been the subject of much discussion by psychologists. There’s a useful review by Levitis et al here. A definition of behaviour the authors decided reflected consensus is:

Behaviour is: the internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal and/or external stimuli, excluding responses more easily understood as developmental changes.

traits and states

Trait is a term used to describe a consistent pattern in behaviour, personality etc. State is used to describe transient behaviours or feelings.

David Didau’s argument

David begins with the point that behavioural traits in adulthood are influenced far more by genes than by shared environments during childhood. He says: “Contrary to much popular wishing thinking, shared environmental effects like parenting have (almost) no effect on adult’s behaviour, characteristics, values or beliefs.* The reason we are like our parents and siblings is because we share their genes. *Footnote: There are some obvious exceptions to this. Extreme neglect or abuse before the age of 5 will likely cause permanent developmental damage as will hitting someone in the head with a hammer at any age.”

In support he cites a paper by Thomas Bouchard, a survey of research (mainly twin studies) about genetic influence on psychological traits; personality, intelligence, psychological interests, psychiatric illnesses and social attitudes. David rightly concludes that it’s futile for schools to try to teach ‘character’ because character (whatever you take it to mean) is a stable trait.

traits, states and outcomes

But he also refers to children’s behaviour in school, and behaviour encompasses traits and states; stable patterns of behaviour and one-off specific behaviours. For David, school expectations can “mediate these genetic forces”, but only within school; “an individual’s behaviour will be, for the most part, unaffected by this experience when outside the school environment”.

He also refers to “how we turn out”, and how we turn out can be affected by one-off, even uncharacteristic behaviours (on the part of children, parents and teachers and/or government).   One-off actions can have a hugely beneficial or detrimental impact on long-term outcomes for children.

genes, environment and interactions

It’s easy to get the impression from the post that genetic influences (David calls them genetic ‘forces’ – I don’t know what that means) and environmental influences are distinct and act in parallel. He refers, for example, to “genetic causes for behaviour as opposed to environmental ones” (my emphasis), but concedes “there’s definitely some sort of interaction between the two”.

Obviously, genes and environment influence behaviour. What’s emerged from research is that the interactions between genetic expression and environmental factors are pretty complex. From conception, gene expression produces proteins; cells form, divide and differentiate, the child’s body develops and grows. Genetic expression obviously plays a major role in pre-natal development, but the proteins expressed by the genes very quickly form a complex biochemical, physiological and anatomical environment that impacts on the products of later genetic expression. This environment is internal to the mother’s body, but external environmental factors are also involved in the form of nutrients, toxins, activities, stressors etc. After birth, genes continue to be expressed, but the influence of the external environment on the child’s development increases.

Three points to bear in mind: 1) A person’s genome remains pretty stable throughout their lifetime. 2) The external environment doesn’t remain stable – for most people it changes constantly.  Some of the changes will counteract others; rest and good nutrition can overcome the effects of illness, beneficial events can mitigate the impact of adverse ones. So it’s hardly surprising that shared childhood environments have comparatively little, if any, effect on adult traits.   3) Genetic and environmental influences are difficult to untangle due to their complex interactions from the get-go. Annette Karmiloff-Smith* highlights the importance of gene-environment-behaviour interactions here.

Clearly, if you’re a kid with drive, enthusiasm and aspirations, but grow up on a sink estate in an area of high social and economic deprivation where the only wealthy people with high social status are drug dealers, you’re far more likely to end up with rather dodgy career prospects than a child with similar character traits who lives in a leafy suburb and attends Eton. (I’ve blogged elsewhere about the impact of life events on child development and long-term outcomes, in a series of posts starting here.)

In other words, parents and teachers might have little influence over behavioural traits, but they can make a huge difference to the outcomes for a child, by equipping them (or not) with the knowledge and strategies they need to make the most of what they’ve got. From other things that David has written, I don’t think he’d disagree.  I think what he is trying to do in this post is to put paid to the popular idea that parents (and teachers) have a significant long-term influence on children’s behavioural traits.  They clearly don’t.  But in this post he doesn’t make a clear distinction between behavioural traits and outcomes. I suggest that’s one reason his post resulted in so much heated discussion.

genes, environment and the scientific method

I’m not sure where his argument goes after he makes the point about character education. He goes on to suggest that anyone who queries his conclusions about the twin studies is dismissing the scientific method, which seems a bit of a stretch, and finishes the post with a series of ‘empirical questions’ that appear to reflect some pet peeves about current educational practices, rather than testing hypotheses about behaviour per se.

So it’s not surprising that some people got hold of the wrong end of the stick. The behavioural framework including traits, states and outcomes is an important one and I wish, instead of going off at tangents, he’d explored it in more detail.

*If you’re interested,  Neuroconstructivism by Mareschal et al and Rethinking Innateness by Elman et al. are well worth reading on gene-environment interactions during children’s development.  Not exactly easy reads, but both reward effort.


Bouchard, T. (2004).  Genetic influence on human psychological traits.  Current Directions in Psychological Science, 13, 148-151.

Elman, J. L., Bates, E.A., Johnson, M., Karmiloff-Smith, A., Parisi, D., & Plunkett, K. (1996). Rethinking Innateness: A Connectionist Perspective on Development.  Cambridge, MA: MIT Press.

Karmiloff-Smith A (1998). Development itself is the key to understanding developmental disorders. Trends in Cognitive Sciences, 2, 389-398.

Levitis, D.A., Lidicker, W.Z., & Freund, G. (2009).  Behavioural biologists don’t agree on what constitutes behaviour.  Animal Behaviour, 78 (1) 103-110.

Mareschal, D., Johnson, M., Sirois, S., Spratling, M.W., Thomas, M.S.C. & Westermann, G. (2007). Neuroconstructivism: How the brain constructs cognition, Vol. I. Oxford University Press.