Twin Study Sheds Light on Nature vs Nurture Debate

Is our brain’s wiring determined by our genes or shaped by our experiences? Thanks to advances in neuroimaging and the unique framework offered by twin studies, researchers can now delve deeper into this question, mapping the brain’s response to emotional and cognitive challenges and determining how much of it is influenced by biology versus life experiences.

Researchers at UNSW Sydney and Neuroscience Research Australia (NeuRA) have undertaken such an investigation, using functional MRI (fMRI) to study the brains of twins as they performed various cognitive and emotional tasks.

The findings shed light on how specific brain functions are shaped by genetic inheritance and environmental context, offering a richer understanding of mental wellbeing and psychological vulnerability.

The research was published in the journal Human Brain Mapping.

Nature vs nurture twin studies

Twin studies are uniquely suited to separating the effects of nature and nurture:

• Identical twins (monozygotic) share 100% of their genes.
• Fraternal twins (dizygotic) share approximately 50% of their genes.
• Both types typically share a similar environment during development.

By comparing patterns of brain activity between these groups, researchers can estimate the heritability of specific brain functions, essentially asking how much variation can be attributed to genetic differences.

“With twin studies, it’s important to recruit both identical and non-identical twins,” said Associate Professor Justine Gatt. “Identical twins share 100% of their genetics and if they're grown up together, they share the same environment. Whereas with the non-identical twins, they only have 50% shared genetics, but they also have that common environment.”

Nature vs nurture studies, an example

The study is part of the broader TWIN-E project, which recruited 1,600 twins from across Australia. A subset of 270 twins participated in this brain imaging phase. Each participant underwent an fMRI scan while completing five distinct tasks:

Emotional tasks

1. Facial expression recognition: Participants viewed faces displaying different emotions, such as fear or happiness.
2. Emotional conflict processing: Tasks that required interpreting conflicting emotional stimuli.

Cognitive tasks

3. Sustained attention tasks: Tests measuring an individual's ability to maintain focus over time.
4. Short-term memory recall: Tasks involving remembering and manipulating information over a brief period.
5. Response inhibition: Tasks designed to assess the ability to control impulsive behaviors.

Participants completed these tasks while wearing specialized goggles in the fMRI scanner, which allowed them to view the visual stimuli directly. The scanner measured brain activation in real time.

“The functional tasks involve them viewing different images, different stimuli, through the goggles,” explained Gatt.

The researchers used twin modelling to analyze the brain imaging data. This statistical technique evaluates how much variance in a trait – in this case, brain activation – can be attributed to genetic versus environmental factors.

Twin studies: modelling results

The study produced two central findings:

1. Task-specific genetic and environmental contributions

Some tasks showed a clear genetic influence, while others were shaped more by environment.

“We found that for some of these networks, genetics plays a small to moderate, but significant role,” said Gatt. “And for other processes, it’s only the environment that determines brain function.”

For instance:

• Genetics played a role in how participants processed emotional facial expressions.
• Environment was more influential in shaping performance in working memory tasks.

These finding challenge assumptions that all aspects of brain function are either primarily genetic or environmental, showing instead a nuanced, task-specific relationship.

2. Overlap across emotional and cognitive domains

Another result was the discovery that some genetic or environmental influences were shared across different kinds of tasks.

“We discovered that how the brain processes fear and happiness (which was measured in the emotional tasks) and our ability to sustain attention (which was measured in the cognitive tasks), have some shared genetic factors,” said Dr. Haeme Park, lead author.

Credit: iStock.

Additionally, shared environmental factors were identified between sustained attention and working memory, suggesting that common life experiences – like education, parenting or lifestyle – may influence multiple cognitive abilities in a similar way.

Nature vs nurture: Implications for mental health and wellbeing

Understanding the balance between heritability and environment has powerful implications for mental health research and intervention design. Brain functions influenced by environment may be more malleable, offering opportunities for improvement through therapy, training or lifestyle changes.

“This study is interesting because we have further insight into how much of our life experiences modulate certain brain processes, which to a certain degree we have more control over, versus your biology, which you can’t change,” said Gatt.

Knowing whether a particular cognitive pattern is environmentally shaped can guide more targeted mental health treatments, particularly for individuals at risk for anxiety, depression or attentional disorders.

“If someone has a tendency to attend to negative stimuli more than positive, and we know that there's an element of environment contributing to that, with intervention or training, it’s potentially something we can target and improve for the better,” Gatt added.

A longitudinal view: The decade-long follow-up

The same participants have now completed follow-up assessments a decade after their original scans, performing the same tasks again. This will allow researchers to explore how genetic and environmental contributions to brain activity may shift with age and life changes.

“We’re using this data […] actually predicting mental wellbeing and resilience trajectories over time,” said Gatt, “and seeing how differences in markers like brain function and structure might profile people who are a bit more resilient or at more risk to a mental health problem.”

The longitudinal aspect of the study offers a unique opportunity to track not only static brain patterns, but also how biology and experience interact dynamically across a person’s life.

Frequently asked questions

1. What does "nature vs nurture" mean?
   "Nature vs nurture" refers to the debate about whether genetics (nature) or environment and life experiences (nurture) play a greater role in shaping our behavior, personality, and mental processes.
2. How do twin studies help in understanding nature vs nurture?
   Twin studies compare identical and fraternal twins to separate genetic influences from environmental ones, helping researchers estimate how much of a trait is inherited.
3. Why are identical twins particularly important in this research?
   Identical twins share 100% of their genetic material. Differences between them can therefore be attributed to environmental influences, making them ideal for nature vs nurture studies.
4. What types of brain functions are studied in twin research?
   Researchers examine cognitive functions like memory, attention and impulse control, as well as emotional responses, decision-making and risk for mental health disorders.
5. Can environment really change how the brain works?
   Yes. Environmental factors such as education, stress, relationships and therapy can significantly shape brain structure and function over time.

Reference: Park HRP, Chilver MR, Quidé Y, et al. Heritability of cognitive and emotion processing during functional MRI in a twin sample. Hum Bra Map. 2024. doi: 10.1002/hbm.26557

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