The Value of Longitudinal Developmental Studies

family of four with a clock behind them

You, or your partner, are pregnant, nearing the due date. At a routine check-up, your doctor informs you of a longitudinal research study that will be starting soon which will follow children’s development from birth through adolescence. Once a year for the next decade, researchers will visit the family’s home to conduct interviews, collect samples, and check in on the family. Both parent and child will be compensated for participating in the study. Participants will also have the satisfaction of knowing their information will contribute to important scientific research. Your doctor informs you that you and your family are eligible to participate.

Would you join the study? I would urge you to say yes.

Longitudinal studies similar to the fictional example above are essential for understanding development in a comprehensive way. While short-term studies are useful and can often provide succinct answers to specific questions, studies that assess the effects of environmental factors on long-term development provide a broader understanding of how development occurs and its potential plasticity. We find a useful comparison in looking at clinical trials of drugs. Short-term trials studying the immediate effects of an experimental drug on patients are absolutely essential. But if patients remain on the drug after the initial experimental period and no researchers check in with them on a regular basis over the next years, the long-term effects of the drug and dosage will remain unmeasured. If potentially life-altering side effects emerged in the years after the conclusion of a short-term clinical trial, they would go unrecorded, and thus doctors could continue to prescribe that medication to patients, exposing them to potential unintended consequences.

The same basic logic applies to the study of child development. Developmental psychology researchers aim to understand both short- and long-term developmental milestones and how individual differences in environment and genetics may influence that development. By building an intricate understanding of how development progresses and can be altered, researchers hope to optimize the environments in which children grow — pioneering interventions and guidelines to help every child succeed.

The research of Steinhardt’s Neuroscience and Education Lab (NEL) focuses on the longitudinal study of children’s development, with a particular interest in self-regulation. The skills that comprise self-regulation throughout childhood and adolescence include cognitive skills known as executive functions, which include working memory, inhibitory control, cognitive flexibility, and emotional regulation — the ability to regulate the physiological and cognitive response to emotionally evocative situations and thoughts — as well as other factors that affect one’s ability to control one’s behavior. These skills are useful and necessary for a myriad of daily activities and have proven key components that facilitate academic, professional, and social success. Researchers now look to self-regulation as a predictive mechanism for continued development — kids with effective self-regulatory skills are more likely to meet other developmental landmarks. More so, recent research from NEL has demonstrated that children with high executive functioning skills but low math knowledge when entering school are able to catch up to their peers who scored higher on the early-math assessment, suggesting that executive function and related self-regulation skills are essential for continued academic success and may be a mediating factor in negotiating childhood risk.

NEL researchers approach the study of self-regulation with a longitudinal lens. Dr. Clancy Blair, one of the lab’s principal investigators, emphasizes the value of investing in this work: “Longitudinal field-based studies provide essential information about processes of development that cannot be gained by cross-sectional, experimental, or even short-term longitudinal studies — by following the same children and families over time for many years we gain insight into the varied patterns and trajectories of human development and the primary variables that influence the following of one trajectory or pattern as opposed to another.” The lab conducts such assessments through two distinct methodologies — through assessments of development over the course of childhood and adolescence, and through targeted early-childhood interventions. NEL is currently gearing up for new rounds of data collection on both of these fronts, through the Family Life Project (FLP) and the Chicago School Readiness Project (CSRP), both of which have been ongoing since 2003. Combined, these two projects track the development of almost 2,000 families in Pennsylvania, North Carolina, and Illinois.

FLP follows the first methodology, gathering participant data on a regular basis and tracking participant development from birth through adolescence. FLP researchers have been collecting data from over 1,200 children and families, using assessments of children’s executive function abilities, stress levels, language development, academic achievement, classroom behavior, and data about children and families’ home lives — if both parents are regularly present in their lives, the families’ level of income, their living conditions, their social networks, and any potential toxic exposures such as domestic violence and tobacco smoke. The study’s wide-reaching data set is partially a product of advances in biomedical sciences, Dr. Blair points out: “we have the opportunity to really integrate biological measures such as genetics, epigenetics, immune function, and metabolic indicators with our traditional measures of environmental experiences to come to increasingly strong and precise conclusions about processes of human development.” FLP recently joined an NIH-funded research initiative aimed at assessing chemical and psychological exposures on child health and development across the country. This initiative brings together over 70 existing cohorts consisting of around 50,000 children and families, hoping to build a data set large enough to tackle some overarching questions about child development.

CSRP, on the other hand, uses an intervention-based study design. Initially, researchers instituted a preschool intervention in Head Start centers located in high poverty neighborhoods in Chicago, where experimental classrooms received targeted programming and supplemental support in hopes of better managing student behavior and enhancing academic success. CSRP’s research design specifically targeted students’ emotional regulation skills, in hopes that supporting these early capacities would have long-term effects on student achievement. In the years following, CSRP researchers have regularly checked-in with participants, gathering data about their academic progress and quality of life, along with continued assessments of executive function and emotion regulation. CSRP is also entering a new round of data collection this spring. As their participants reach young adulthood, researchers are checking back to see how the students are faring and what their future steps might be.

Dr. Tyler Watts, Assistant Research Professor in NYU’s Institute of Human Development and Social Change, who recently joined the CSRP team, emphasizes how rare it is for researchers to follow intervention studies for as long as CSRP has: “We just don’t have enough interventions with longitudinal follow-up. Most of the studies that have actually included long-run follow-up are now quite old.” But longitudinal research is necessary to understand the true effects of an early-childhood intervention, especially one that has potentially long-reaching outcomes. Dr. Watts predicts longitudinal studies of development will become more prevalent in years to come. In addition to data sets from purposeful scientist-designed studies, our automated lives are creating a “data saturation” ripe for analyzing — medical records, test scores, school attendance, college-entrance statistics, and more are automatically compiled by a number of agencies. “All we need are people who are capable of using those data sets appropriately,” Watts adds.

Dr. Cybele Raver, CSRP’s principal investigator, concurs, recognizing the value of longitudinal studies for the population as a whole: “I have learned from ten years of leading CSRP that children’s minds and hearts are our nation’s precious resources. When we invest in students and believe in their potential, so much is possible!” Yet, she understands the commitment this involves, knowing that such studies can only be possible with continued dedication from participants willing to invest their time and energy in pursuit of ambitious goals: “I am grateful to each amazing student and to each and every family in CSRP for showing educators and policymakers the value of believing in children’s futures, right from the start.”  

Building such a database of developmental understanding hinges on one necessary component: families and individuals who are willing to stick with a study for the long-haul. These participants buy-in almost altruistically, often sacrificing time and energy to the pursuit of scientific knowledge, knowing that there may very well be no direct benefit for themselves or their children. Other than the monetary compensation for time and effort, participants often go into a study with little expectation of personal outcome.

Why do people agree to participate in this sort of study? “Oh boy, that’s a hard question.” Dr. Watts suspects their continued participation has something to do with the community-building aspect of study relationships: “Participants really do build a rapport with the Research Assistants that survey them; I think that relationship helps them continue to buy-in, year after year.” Dr. Blair agrees, calling the FLP data assessors who live in the same communities as the participants “the study’s greatest asset.” But those relationships build over time.

I hypothesize it has to do with something more, something larger than all of us. Growth almost always involves sacrifice — of time, of resources, of emotional energy — and parents, perhaps more than anyone, understand this intrinsically. It seems likely that the same drive that parents have to build the best life possible for their own children would motivate them to become and stay involved in developmental studies, knowing they are helping to mitigate progress that will benefit the happiness and success of children, albeit future ones.

In our current era of doubters, disbelievers, and fake news, longitudinal studies such as these remind us of the value that comes from investing seriously in science. But they also demonstrate the quiet bravery of investing in the future, individually and as a whole, and the value of building communities that believe positive change is possible. NEL’s research participants, like those of countless other studies, come back time and time again, willing to undergo sacrifices in service of that vision, and dedicate themselves to the knowledge that even if these researchers may not be able to improve the odds for them or their children, there is a future child for whom they will be able to do so. It is through this communal dedication and these intentional investments in our future that we can fight for progress, better understand our environments and their impacts and, perhaps most importantly, begin to even the developmental playing field to allow every child the ability to reach their maximum potential.

Sierra Adler is Outreach Coordinator for the Neuroscience and Education Lab.