beyond nature vs. nurture

The Scientist | A journalist once asked the behavioral psychologist Donald Hebb whether a person’s genes or environment mattered most to the development of personality. Hebb replied that the question was akin to asking which feature of a rectangle—length or width—made the most important contribution to its area.

The “nature vs. nurture” conundrum was reinvigorated when genes were identified as the units of heredity, containing information that directs and influences development. When the human genome was sequenced in 2001, the hope was that all such questions would be answered. In the intervening decade, it has become apparent that there are many more questions than before.

We’ve reached a point where most people are savvy enough to know that the correct response isn’t “nature” or “nurture,” but some combination of the two. Yet scientists and laymen alike still spend too much time and effort trying to quantify the relative importance of nature and nurture.

Recent advances in neuroscience make a compelling case for finally abandoning the nature vs. nurture debate to focus on understanding the mechanisms through which genes and environments are perpetually entwined throughout an individual’s lifetime. As neurobiologists who study stress, we believe that research in this area will help reframe the study of human nature.

Researchers have historically approached the study of stress from two perspectives: 1) a physiological account of the stress response, which consists of tracking the stress hormone cortisol and its effects on metabolism, immune function, and neural processes; and 2) a psychological/cognitive focus on how the perception and experience of a stressor influences the stress response. These approaches align with the nature vs. nurture debate, pitting nature, represented by the biology of cortisol responses, against nurture, in the form of external experience influencing cognitive processing. Academic researchers typically study stress by adopting one of these perspectives. However, anyone who’s been stuck in rush hour traffic or faced a looming deadline knows that the causes and consequences of stressful experiences do not adhere to these academic divides.

In the past decade, researchers have made great strides in understanding the cellular, molecular, genetic, and epigenetic processes involved in the regulation of the stress response. Surprisingly, as stress research elucidated this molecular dimension, it shed light on the powerful role of environment and experience in remodeling our molecular makeup. It became clear that the environmental effects (nurture) are modulated by genetic polymorphism and epigenetic programming of gene expression (nature) to shape development. So, as the molecular underpinnings are elucidated, the need to study the interaction between environment and our genome is highlighted, and the divide seems less relevant.

Recent advances in stress research (focused on genetic, epigenetic, and molecular events) are inverting implicit assumptions about gene/environment relationships and the nature/nurture divide. The most current data indicate that environments can be as deterministic as we once believed only genes could be, and that the genome can be as malleable as we once believed only environments could be. For example, increased expression of the glucocorticoid receptor gene in particular brain regions improves the ability to regulate a stress response. In the lab we’ve demonstrated that enhanced maternal care provided to young rats serves to permanently increase expression of this gene in brain regions that ultimately influence how the animals respond to stress. Early nurturing regulates the expression of a gene that is crucial to modulating the stress response.

The mind/body divide is disappearing, too, as we discover that mental phenomena have physical correlates, an understanding of which can help us develop new approaches for research, teaching, and policy related to stress and health. While this integrative view of stress probably seems obvious to the average thinking person, it’s taken basic scientists fifty years to reach the same conclusion. The false dichotomy of nature vs. nurture is quickly eroding, and the modern era of stress research makes a compelling case for the study of the dynamic interplay between our genomes and our experiences.