Early Baby Behavior Predicts Adult Cognition and Intelligence

Few scientists however looked back further to see what — if anything—signals in infancy can tell us about cognition in adulthood and old age.

Gustavson and senior author Chandra Reynolds, a professor of psychology and neuroscience, looked at data from 1,098 participants in the Colorado Longitudinal Twin Study. The university’s Institute of Behavioral Genetics (IBG) launched the study in 1985, enrolling baby twins from Colorado’s Front Range to assess the role that genes vs. environment play in various aspects of development. 

As early as 7 months old, researchers assessed 7 measures of cognition, including vocalization, ability to stay on task, and “novelty preference” — whether the infants preferred to play with new toys over ones they were familiar with. 

Age-appropriate cognitive assessments have been done at five points, so far.

The team found that looking at cognitive tests in infancy could predict about 13% of the variance in scores at age 30.

Two measures —novelty preference and task orientation—were the strongest predictors. This early life “signal” is not huge, the authors note. 

To explore what role genetics vs. environment plays, the study compared GCA score differences between identical twins, who share 100% of their genes, and fraternal twins, who only share half of their genes.

In general, if there is greater similarity among identical twins than fraternal twins, this suggests that genes play a strong role in that trait.

As expected, genes played a big role in influencing general cognitive ability, with genetic influences measured by age 7 accounting for about half of the variation in scores at age 30.

But environment also had a significant and lasting impact.

One of the most exciting findings was that 10% of the variability in adult cognitive ability was explained by environmental influences before year one or two.

The older the children got, the more influence genes had and the less environment had.

This suggests that even the pre-preschool environment matters.

Senior author Chandra Reynolds, who studies age-related diseases including Alzheimer’s and dementia, says the findings could have implications not only for how youth do in school or how adults perform at work but also how prone they may be to age-related cognitive decline.

The study also confirms that “polygenic scores” can be a useful tool.

Polygenic scores are single numbers that aggregate a person’s genetic variants to estimate predisposition to a trait, like intelligence. 

For the study, the researchers used genetic data from nearly 1 million individuals gathered via large datasets like 23 and Me to give each of the adult twins a polygenic score based on their own DNA, for cognitive ability. 

Remarkably, the twins’ scores closely matched what would be expected based on their tests when they were babies.