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Nature, nurture, and time: Q&A with Marla Sokolowski

Research from CIFAR’s Child & Brain Development program transforms how we think about early life experiences.


Both the genes you were born with (nature) and the way you were raised (nurture) affect who you are. The details of the interplay between those factors—how some experiences leave lasting scars or which genes predispose people to debilitating diseases—are some of the most important open questions facing science and society today. 

Groundbreaking work on the socio-economic determinants of health in CIFAR programs over the last four decades, by luminaries including the late CIFAR President & CEO Fraser Mustard and the late CIFAR Fellow Clyde Hertzman, has revealed that the way nature and nurture work together is messy. Chalking some percentage of a trait up to “nature” and some to “nurture” is too simple. Not only is there a complex interplay between genes and environment, but also experiences at critical periods in life, like childhood or adolescence, can have disproportionate effects on outcomes later on.

New collaborative research out of CIFAR’s Child & Brain Development program, using data from across the animal kingdom and approaches that span scientific disciplines, demonstrates the various timescales of these effects, from milliseconds to generations. Published as a special feature in the Proceedings of the National Academy of Sciences (PNAS), the collection includes both perspective articles and original research papers that trace the importance of time in the biological embedding of experience.

Marla Sokolowski is a fellow and co-director emerita (2008-2019) in the CIFAR Child & Brain Development program. A University Professor in the Department of Ecology & Evolutionary Biology at the University of Toronto, she was recently awarded the Royal Society of Canada’s Flavelle Medal for her contributions to biological science. She co-edited the PNAS special feature with CIFAR advisors W. Thomas Boyce and Gene Robinson.

What is the key message of the volume?

The big picture is that timing and timescales matter, and they have been neglected. We must bring considerations of time into discussions of child and brain development. 

For those not familiar, what is a special volume of PNAS?

When you have some important, new ideas that might be paradigm-shifting in the field, you can propose a special volume of PNAS on that topic. It’s a procedure to get permission to write it, and in our case the planning, writing, and editing took nearly two and a half years, with many discussions in the Child & Brain Development program and with editors at PNAS.

It’s a real joy to have this body of work come out. I’ve learned a lot working with the editors and all of the people who wrote for the volume. Like everything I’ve done with CIFAR, this has been a positive, life-changing experience. It’s also a great way for Tom Boyce and I to complete our co-directorship of the program, which we did together for about 11 years. 

What are some of the new findings from the articles in this volume?

People used to think that critical period windows were fixed. So, for example, at a certain age the critical window for learning an aspect of language opened, and then it closed. In the first perspective piece, the authors show that these windows are flexible to some extent. There’s plasticity in when these windows open and close, and this plasticity is influenced by environmental factors such as stress.

There’s also the pediatric clock paper, which I think is going to be important for people to use. You see, you can get two eight year olds that are at very different biological and social ages. The authors have developed an epigenetic clock that gives you some idea of not just a child’s chronological age, but of their developmental age. It’s a fascinating paper, and I think it could be that pediatricians use these kinds of clocks to time their interventions.

How has the Child & Brain Development program changed the way we think about early life experience?

There’s been some wonderful research by people in the group. Chuck Nelson’s work in Romanian orphanages is a great example. He showed the negative impact of neglect and that early positive experience with a mother, father, or caring adult, really matters. Now the orphanages have changed and Romanian people are more willing to adopt kids because of his work. Tom Boyce’s theory of “orchid” and “dandelion” children has also really made a difference to families and children around the world. Those are really substantial paradigm shifts.

“When you actually look at the mechanistic details of the science, it’s overwhelmingly complex.”

When you actually look at the mechanistic details of the science, it’s overwhelmingly complex. It really takes a group of people with different areas of expertise, like CIFAR’s Child & Brain Development program, to come together to understand it. A lot of people in the field look to our program and pay attention to the things that we write and present. If you go to any conference on any topic related to this, there’s usually someone from the program presenting. And because of our experience in CIFAR meetings, we’re really good at facilitating the discussion.

What should parents take away from this research?

Early childhood and adolescence are times of incredible growth and development. During these time periods the brain acts like a sponge, absorbing our experiences and rewiring itself accordingly. The types and quality of experiences during these periods really matter for how our brains and bodies function throughout our lives.

“Scientists are now able to study the importance of the timing of our experiences at the level of nervous transmission, molecules, cells, brain circuits, and gene expression”

Our PNAS volume addresses the importance of the timing of experiences for the interplay of nature and nurture. Scientists are now able to study the importance of the timing of our experiences at the level of nervous transmission, molecules, cells, brain circuits, and gene expression, enabling us to build an understanding of how our early experiences affect our long-term health and behaviour. Interestingly, in some cases our experiences are carried into the next generation. 

For parents, I think it’s important to understand that childhood experiences can really have lifelong effects. That makes the fit between the child and the environment, and the fit with that parent, crucial. The other lesson from this research is that nothing is fixed. You can have predispositions that might have origins in inheritance or genetics, but your environment and your experience can make a big difference.


The interview above has been edited for length and clarity.

The special feature, Biological Embedding Across Timescales, was published in PNAS on September 22, 2020. The volume was inspired by many discussions at Child & Brain Development meetings and co-edited by former Child & Brain Development program co-directors Marla Sokolowski (University of Toronto) and W. Thomas Boyce (University of California, San Francisco) and advisor Gene Robinson (University of Illinois at Urbana-Champaign). 

It contains articles authored by many members of CIFAR’s Child & Brain Development program:

Ina Anreiter (CIFAR program reporter, University of Toronto), Maria Aristizbal (former CIFAR post-doctoral fellow, Queen’s University), Elisabeth Binder (CIFAR Advisory Committee Chair, Max Planck Institute of Psychiatry), W. Thomas Boyce (CIFAR Advisor, University of California, San Francisco), Ami Citri (CIFAR Azrieli Global Scholar 2016-2018, CIFAR Fellow, The Hebrew University of Jerusalem), David Forrest Clayton (CIFAR Associate Fellow, Queen Mary University of London), Brian Dias (CIFAR Azrieli Global Scholar 2017-2019, CIFAR Associate Fellow, University of Southern California), Paul Frankland (CIFAR Fellow, University of Toronto), Anna Goldenberg (CIFAR Lebovic Fellow, Canada CIFAR AI Chair, University of Toronto/Vector Institute), Takao Hensch (CIFAR Co-Director, Harvard University), Daniela Kaufer (CIFAR Associate Fellow, University of California, Berkeley), Michael Kobor (CIFAR Fellow, University of British Columbia), Bryan Kolb (CIFAR Associate Fellow, University of Lethbridge), Joel Levine (CIFAR Fellow, University of Toronto at Mississauga), Thomas McDade (CIFAR Fellow, Northwestern University), Michael Meaney (CIFAR Advisor, McGill University), Sara Mostafavi (Fellow, Canada CIFAR AI Chair, University of British Columbia/Vector Institute), Charles Nelson (Fellow, Harvard University), Candice Odgers (CIFAR Co-Director, University of California, Irvine), Nadine Provençal (CIFAR Azrieli Global Scholar 2020-2022, Simon Fraser University), Kieran O’Donnell (CIFAR Azrieli Global Scholar 2016-2018, CIFAR Fellow, McGill University), Rebecah Reh (former CIFAR post-doctoral fellow, University of British Columbia), Gene Robinson (CIFAR Advisor, University of Illinois at Urbana–Champaign), Marla Sokolowski (CIFAR Fellow, University of Toronto), Jenny Tung (Fellow, Duke University), Janet Werker (CIFAR Advisory Committee Chair for the Brain, Mind & Consciousness program, University of British Columbia)

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