In psychology, nurture refers to every environmental influence that shapes who you become after conception. It includes your family, culture, economic circumstances, education, relationships, nutrition, and lived experiences. The term exists primarily as one half of the “nature vs. nurture” debate, which asks how much of human development comes from inherited biology versus the environment. Modern psychology has largely moved past treating these as opposing forces, recognizing that genes and environment constantly interact.
What Counts as “Nurture”
The American Psychological Association defines nurture as the environmental factors that contribute to individual development, in contrast to hereditary and constitutional factors. That definition is broad on purpose. Nurture encompasses everything from how your parents raised you and the economic stability of your household to the cultural norms you absorbed, the language spoken around you, the food you ate, and the neighborhood you grew up in.
Psychologists typically group these influences into a few categories. Social factors include parenting style, peer relationships, and family dynamics. Cultural factors cover religious practices, societal expectations, and media exposure. Physical and material factors include nutrition, exposure to toxins, and access to healthcare. Economic factors, like household income and parental education level, cut across all of these. A child growing up in poverty, for instance, faces a different constellation of environmental pressures than one growing up in a wealthy suburb, and those pressures have measurable effects on the brain.
Philosophical Roots of the Idea
The nurture perspective has deep philosophical roots. John Locke, the 17th-century English philosopher, argued that the human mind starts as a “tabula rasa,” a blank slate. In his view, knowledge comes not from innate ideas but from experience and observation. This empiricist tradition laid the groundwork for later psychological schools that emphasized learning and environment over biology.
The most extreme version of this position came from the behaviorists in the early 20th century. John Watson believed humans inherit only a few basic reflexes and three emotions (love, rage, and fear), and that everything else is learned. His framework treated learning as simple connections between environmental events and behavioral responses. B.F. Skinner pushed this further, arguing that the environment ultimately determines both external behavior and internal experiences like thoughts and feelings. In Skinner’s view, even your private mental life is shaped by environmental consequences: behaviors that get rewarded persist, and those that don’t get extinguished.
How Environment Physically Changes the Brain
Nurture isn’t just an abstract concept. Environmental input physically reshapes neural tissue. Some of the clearest evidence comes from animal studies on enriched versus standard environments. Mice raised in large cages with toys, running wheels, tunnels, and social companions develop measurably different brains than mice raised in bare cages. In one line of research, mice in enriched environments had 15% more neurons in a key memory region of the brain. Another study found 67% more new neurons in enriched mice compared to those in standard housing. These animals also showed increased cortical thickness, more synaptic connections, and higher levels of a protein (BDNF) that supports neuron growth and survival.
The takeaway for humans is straightforward: stimulating environments build more connected, more adaptable brains. Deprived environments do the opposite. Research published in PNAS found that socioeconomic status had a significant independent association with both brain surface area and working memory in 14-year-olds, even after accounting for genetic factors. Parental education was the strongest driver among economic variables. Notably, socioeconomic status also predicted how brain surface area changed over time, while genetic scores did not. In other words, environment was shaping the trajectory of brain development in ways that genetics alone could not explain.
Critical Windows for Environmental Input
Some aspects of development depend on receiving the right environmental input at the right time. These are called critical periods, and language offers the most striking example. Research has found that the critical period for acquiring basic sentence structure in a first language ends during the first year of life. Congenitally deaf children who receive no language input during that first year develop lasting impairments in their ability to understand and produce complex sentences, even if they receive language input later. The same pattern appears in children who experienced severe nutritional deficiency during infancy: the brain structures that support syntax fail to develop normally when deprived of crucial micronutrients during that window.
This doesn’t mean learning stops after infancy. The brain remains adaptable throughout life, a property called neuroplasticity. But certain foundational skills require environmental input during specific developmental windows, and missing those windows creates deficits that are difficult or impossible to fully overcome.
How Genes and Environment Interact
The old framing of “nature versus nurture” implied a clean split: some traits come from genes, others from environment. Modern psychology recognizes this is misleading. Genes and environment are deeply entangled in at least two important ways.
First, your environment can change how your genes behave. Through a process called epigenetics, environmental factors cause chemical modifications to your DNA that turn genes on or off without changing the genetic code itself. One well-studied mechanism involves small chemical tags (methyl groups) attaching to specific gene sites. These tags can alter gene activity and persist through cell division. Stress, nutrition, toxin exposure, and immune system activation can all add or remove these tags, meaning your life experiences literally edit which parts of your genetic blueprint get used.
Second, genes and environment are correlated in ways that blur any simple boundary between them. Psychologists describe three types of gene-environment correlation:
- Passive: Parents pass on both their genes and a home environment shaped by those same genes. A musically talented parent gives their child both music-related genes and a home full of instruments and concerts.
- Evocative: A child’s genetically influenced traits pull certain responses from the environment. A naturally sociable toddler gets more social interaction from caregivers and peers, amplifying a trait that started as partly genetic.
- Active: As children grow and gain autonomy, they seek out environments that match their genetic predispositions. An intellectually curious teenager gravitates toward libraries and debate clubs, creating an environment that further develops their abilities.
These correlations mean that what looks like a purely “environmental” effect often has a genetic component, and what looks genetic is often amplified or suppressed by environment.
How Much Does Nurture Actually Matter?
Intelligence offers a useful case study because it has been extensively measured. Twin and family studies in industrialized countries estimate that 50 to 80% of the variation in IQ scores is associated with genetic factors, with heritability estimates reaching as high as 0.80 in fully adult populations. That might sound like nurture plays a minor role, but these numbers require careful interpretation.
A study of 486 adoptive and biological families estimated heritability of IQ at 0.42, with the direct environmentally mediated effect of parental IQ scores on offspring IQ estimated at just 0.01. However, gene-environment correlation may account for up to 30% of the variance in adult IQ. That means a large portion of what gets statistically attributed to “genes” is actually genes and environment working together. The high heritability of IQ in wealthy countries partly reflects the fact that when environments are relatively similar (most children get adequate nutrition, schooling, and healthcare), genetic differences become more visible. In populations with wider environmental variation, nurture’s measurable contribution grows.
Beyond IQ, nurture’s influence is even more apparent in traits like language, political beliefs, religious affiliation, and specific skills. No gene makes you speak Mandarin or play piano. Those are entirely products of environmental exposure and practice, even if genetic factors influence how quickly you pick them up.