Scientists and parents have long been interested in understanding how a child's genetic "blueprint" and the environment in which he or she lives interact to affect development. A recent study supports the idea that there are multiple windows of opportunity during which what a child is exposed to in daily life can make big differences in his or her cognitive (mental) development, both at that time and in the future. More importantly, these windows of opportunity open much earlier in childhood than realized and missed opportunities have more negative impact than we might like to believe. The study found that being a toddler of low socioeconomic status can actually prevent a child from realizing the his or her genetically-endowed cognitive potential.

Genes don't always give us a fixed blueprint. Sometimes, they provide us with a potential which might not come out according to plan.

Many of our personal characteristics such as appearance, personality, and health are dependent on our genetic make-up. Some are a direct reflection of the coding of our genetic material and some are dependent on the interaction between our genes and our environment, both during gestation and after birth. This means, that genes don't always give us a fixed blueprint. Sometimes, they provide us with a potential which might not come out according to plan. Exposure to toxic substances, microbes, environmental stimuli, neurobiologic stressors, and many more unexpected influences help determine how predictably a genetic plan unfolds.

This understanding, that genetic contributions are influenced – positively and negatively – by the environment, has prompted a wealth of fascinating questions: Can all genetic blueprints be influenced? What types of influences make a difference? Does it matter how much and at what point in development these exposures occur? Can negative influences be compensated for, changed, or predicted? Can we specifically plan positive influences to improve genetic outcome?

Environmental Influences Determine Whether Genetic Potentials Are Realized

This awareness of the interaction between genes and the environment has also changed our fledgling understanding of the double helix of DNA. Genetic contributions are no longer seen as providing unchangeable building blocks. Instead, a child's genetic inheritance is viewed as a set of developmental potentials subject to and actually dependent on non-genetic influences (parents, siblings, nutrition, stimulation, environmental stressors and toxins, and many other influences) in order to fully express its potential.

A recent study by researchers at the University of Texas, Austin, found that a child's environment, even as early as birth to two years, makes a big contribution to his or her cognitive development.

Mental Abilities Develop Along Pathways
Cognitive development begins at birth and progresses along predictable pathways. All parents are familiar with the developmental milestones, checked at regular intervals throughout children's lives. Many skills develop sequentially, building on previous ones to achieve new abilities. For example, children must learn to use their hands to manipulate objects in order to be able to explore and learn about them. Similarly, they must be capable of moving about the environment to gain information about its rewards and risks.

Many skills develop sequentially, building on previous ones to achieve new abilities. For example, children must learn to use their hands to manipulate objects in order to be able to explore and learn about them.

A child must also have the opportunity to engage with interactive adults to learn and to develop social, emotional, and communication skills. The role of the environment in the expression of a child's genetic cognitive potential has been well researched. The research has suggested that children benefit from positive exploration of physical, emotional, and social environments.

The Impact of Environmental Stimuli
In the recent study researchers followed 750 pairs of twins from a variety of locations, ethnicities and incomes. They wanted to see if the children's cognitive potential, which should be able to be fairly accurately predicted by their parents' cognitive abilities, could in fact be predictable, regardless of their socioeconomic environment.

The investigators reasoned that if genes require certain environmental stimuli in order to be expressed, then restrictive environments of low socioeconomic status, such as growing up in poverty, in a home with substance abuse, mental illness, and low education; or in a poor neighborhood, and deprived environment would prevent the full expression of genetic potential. This is precisely what they found.

They measured cognitive ability with standardized tests administered at ages 10 months and then again at 24 months of age. If cognitive abilities were primarily genetic, the range of scores on these tests would remain pretty much the same when the groups were tested at each age.
Environment Out-Influences Genes

At 10 months, there was no difference in how the children from different socioeconomic backgrounds performed. They showed a statistically predictable range of abilities, based on parental IQ. When they re-measured the twins at 24 months, they expected to find the same ranges of IQ, the standard bell shaped curve with most in the average range, few in the higher and lower ranges.

Although the children may have had the genes to achieve higher levels of development, they were literally restricted in their ability to develop by lack of opportunity, influence, stimulation, and feedback.

By 24 months, however, children from high socioeconomic backgrounds were more likely to achieve the higher scores predicted by their parents' abilities than those children with parents of similar ability from low socioeconomic backgrounds. Although the genes of the children in poorer, lower SES environments should have enabled them to achieve higher levels of development, they were literally restricted in their ability to develop by lack of opportunity, influence, stimulation, and feedback. The degree to which genes influenced mental development differed according to a child's socioeconomic situation. By 2 years, genetic influences on mental ability were larger for children being raised in higher-SES homes than for children being raised in lower-SES homes.

Similarly, there also appears to be a predictable relationship between a child's lower SES level and the decreased development of cognitive skills by 24 months. As a child's socioeconomic status decreased, so did the ability of the genes to positively influence the child's ultimate cognitive outcome. As researcher Elliot Tucker-Drob, an assistant professor of psychology put it in a university press release, "Socioeconomic disadvantages suppress children's genetic potentials."

According to Tucker-Drob, 'For children from poorer homes, genetic influences on changes in cognitive ability were close to zero. For children from wealthier homes, genes accounted for about half of the variation in cognitive changes.'

Studies have shown that children living in lower SES environments may have adults who are less physically and emotionally available in their lives. Such adults may be stressed by social/emotional pressures, multiple jobs, illness, substance use, mental illnesses, responsibility for multiple family members, isolation as single parents, minimal education and less connection to community and to social services. It is not surprising that their availability to play peek-a-boo or take their children to the park is limited.

An Early Boost – Or Not

But what this means is that children from families who are emotionally and physically available to them and can afford to provide nurturing and appropriately safe and stimulating environments, as well as significant amounts of age-appropriate interactive play, get a boost in their cognitive development that other kids don't get. According to Tucker-Drob, "For children from poorer homes, genetic influences on changes in cognitive ability were close to zero. For children from wealthier homes, genes accounted for about half of the variation in cognitive changes."

The critical message of this study is how very early the influence environment plays a role in influencing genetic potential. It clearly occurs before the children are school age, before Head Start, and in even before most programs that currently attempt to compensate for the infant deprivation suffered in low SES homes. This does not diminish the positive influence of early childhood education and stimulation programs, including head start and preschool. It, does however, suggest, that we need to target even earlier years for our most vulnerable populations even as we attempt to decrease the reasons for socioeconomic deprivation in our population..

This research adds to the literature supporting the importance of the earliest childhood experiences in intellectual development and opens numerous areas of research from the neurobiology of cognitive development and environmental interaction, to the needs for social policies, family support, and early childhood programs.