How Genetic Conflict Shapes Human Psychology and Behaviour

People tend to believe they have complete command over their choices and behaviour. Yet beneath conscious awareness, factors outside our control shape the way we think and act: our genes.

Since the 1950s, scientists have investigated the effects genes can have on human health.

That work has prompted clinicians, researchers and policymakers to support precision medicine, which tailors the diagnosis and treatment of illnesses to individuals and can bring faster improvements in patients’ well-being.

However, the role genes play in psychology has received far less attention.

My research examines the ways genes affect human psychology and behaviour. Genetic conflict theory offers psychologists several ways to understand human behaviour more effectively – and may also help improve treatment for psychological problems.

What role do genes play?

Genetic conflict theory suggests that, although our genes combine to make us who we are, they retain signals of whether they were inherited from our mother or father. As we grow and develop, those signals can lead genes to cooperate or compete with each other.

Genetic conflict research has chiefly concentrated on pregnancy, one of the rare points in human development when the effects of distinct groups of genes can be directly seen within a single person.

Maternal and paternal genes generally have different preferred approaches to growth and development. Although genes from each parent ultimately cooperate in ways that support typical growth and development, they can benefit from steering fetal development slightly closer to what is best for the parent from whom they originated.

Genes inherited from the mother favour keeping her healthy and preserving sufficient resources for another pregnancy. Genes inherited from the father, meanwhile, benefit when the fetus draws all of the mother’s resources for itself.

If the genes cannot reach a compromise, the consequences may be harmful, including physical and mental impairments for the baby or even miscarriage.

Although genetic conflict is normal, psychology has largely overlooked its effects. One reason is that researchers assume genetic cooperation is required for an individual’s health and well-being.

A further reason is that the majority of human traits are governed by numerous genes. Height, for instance, is shaped by a combination of 10,000 genetic variants, while skin colour is influenced by more than 150 genes.

Because psychology and behaviour are so complex, it is difficult to isolate the particular effect of one gene, much less establish which parent supplied it.

Depression is one example. The chance of developing depression is affected not only by 200 different genes, but also by environmental factors, including childhood maltreatment and stressful life events. Researchers have examined similarly complex interactions in stress- and anxiety-related disorders.

Prader-Willi and Angelman syndromes

Studies of genetic conflict have generally explored its relationship with illness, inadvertently recording the ways genetic conflict can affect psychology.

In particular, researchers have explored extreme forms of genetic conflict – where one group of parental genes is expressed in full and the other is entirely silenced – through people with Prader-Willi syndrome and Angelman syndrome, documenting the associated behavioural changes.

Prader-Willi and Angelman syndromes are uncommon genetic conditions, affecting around 1 in 10,000 to 30,000 and 1 in 12,000 to 20,000 people worldwide, respectively. Neither condition currently has a long-term treatment.

These syndromes arise when patients lack one copy of a gene on chromosome 15 that is necessary for balanced growth and development. A person who inherits only their father’s version of the gene develops Angelman syndrome, whereas a person with only their mother’s version develops Prader-Willi syndrome.

Key physical features of Angelman syndrome include substantial developmental delays, intellectual disabilities, difficulties with movement and eating, and excessive smiling.

The physical features of Prader-Willi syndrome include reduced muscle tone, feeding problems, hormone deficiencies, short stature and extreme overeating during childhood.

These conditions are among the few cases in which the effects of one absent gene can be observed clearly. Both Angelman syndrome and Prader-Willi syndrome are linked to difficulties with language, cognition, eating and sleep, but they are also associated with distinct psychological and behavioural differences.

For instance, children with Angelman syndrome smile and laugh, and are typically keen to take part in social interactions. Such behaviours are linked with a greater capacity to obtain resources and investment from people around them.

By contrast, children with Prader-Willi syndrome can have tantrums and anxiety, and struggle in social settings. These behaviours are linked to greater difficulties for mothers early in the person’s life, potentially postponing the point at which their mother has another child.

As a result, the child would have greater access to resources, including food and parental attention.

Genetic conflict in psychology and behaviour

Angelman syndrome and Prader-Willi syndrome demonstrate why it matters to examine the effects of genetic conflict on psychology and behaviour. Researchers have identified differences in temperament, sociability, mental health and attachment in these conditions.

The contrasting psychological processes associated with these syndromes resemble the predicted consequences of genetic conflict. Through differences in behaviour and resource requirements, genetic conflict affects attachment by shaping the responsiveness and sensitivity within the parent-child relationship.

That relationship starts to form while the child remains in the womb, helping to calibrate how strongly they respond to different social circumstances. Although this adjustment of responses begins as a biological process in utero, it produces distinctive social behaviour patterns that affect everything from the way we cope with stress to our personalities.

As most scientists do not take genetic conflict into account when studying human behaviour, much of this work remains theoretical. To understand how the biological process of genetic conflict shapes psychological processes, researchers have had to identify connections between different disciplines.

Research into Angelman syndrome and Prader-Willi syndrome is only one illustration of how incorporating a genetic conflict framework into psychological research gives researchers a route to investigate how biology makes us uniquely human.

Jessica D. Ayers, Assistant Professor of Psychological Science, Boise State University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.