In a groundbreaking study published in Psychoneuroendocrinology, researchers have uncovered a significant connection between genetic factors and the behavior of infants when it comes to cuddling and seeking touch. This study, focusing on seven-month-old infants, sheds new light on the biological foundations of social bonding in infancy.
The impetus behind this study stems from a desire to comprehend the underpinnings of human development, particularly in the context of social behavior and physical touch. Previous research has emphasized the importance of caregiving and pleasant touch in the growth and development of human infants.
Touch is not just a physical sensation but plays a critical role in forming social bonds and emotional well-being. Understanding the genetic factors that might influence these interactions could shed light on the complexities of human development and social interactions from the earliest stages of life.
“I’m generally interested in the developmental and brain origins of human social behavior. Social touch and its neurobiological basis is an important, yet little understood, aspect of early social interactions and experiences,” explained study author Tobias Grossmann, a professor of psychology at the University of Virginia.
The study was conducted in Leipzig, Germany, involving 98 infants of Western European descent, all seven months old. To ensure a clear focus, the infants chosen were healthy, with no reported developmental issues or family history of autism spectrum disorder. However, only 82 of these infants were included in the final analysis due to the availability of necessary data.
To explore the genetic aspect, researchers collected saliva samples from the infants and their mothers for genotyping – a process to identify specific genetic variants. They focused on a gene known as CD38, which previous studies have linked to oxytocin release. Oxytocin, often dubbed the ‘love hormone,’ is crucial for social interaction and maternal behaviors. It facilitates bonding between parents and infants and plays a role in empathy, trust, and relationship-building throughout life.
In addition to genetic analysis, the study heavily relied on parental observations. Parents completed a questionnaire known as the Infant Behavior Questionnaire-Revised, which assesses various infant temperament traits. One of these traits was ‘cuddliness’ – the tendency of an infant to seek and enjoy physical contact with their caregivers. This measure provided a unique window into the infants’ day-to-day behaviors and preferences in their natural environment.
The researchers found that infants with certain variations of the CD38 gene were found to exhibit higher levels of cuddliness compared to those with different genetic makeups. Specifically, infants with the CA and AA genotypes displayed a stronger inclination to seek and enjoy caregiver touch than those with the CC genotype. The CA and AA genotypes have previously been linked with increased release of oxytocin.
“We probably all know from experience that people differ in their motivation to seek out and enjoy social touch,” Grossmann told PsyPost. “Our study suggests that such individual differences start early in life and are, at least partly, explained by genetic variability in the oxytocin system.”
In a bid to ensure the robustness of their findings, the researchers conducted additional analyses. These control tests confirmed that the observed effect was indeed specific to the cuddliness trait and directly linked to the infant’s genetic makeup, not influenced by other factors like the mother’s genotype or the infant’s general activity level.
Further, the study ventured into assessing the long-term stability of cuddliness. It found that cuddliness at seven months had a positive correlation with cuddliness at 18 months, suggesting that this trait is relatively stable over time in infancy.
Despite its insightful findings, the study acknowledges certain limitations. For one, it relies heavily on parental reports, which, while valuable, can be subjective. Future research could benefit from more direct experimental methods to assess infants’ responses to social touch. Additionally, a more comprehensive approach to studying the oxytocin system, including multiple genetic and epigenetic factors, could offer a deeper understanding.
“We only examined genetic variability for one specific gene in the oxytocin system,” Grossmann said. “Future research needs to extend this approach by employing experimental methods to measure individual differences in infants’ cuddliness using more comprehensive genotyping and hormonal assays.”
The study also points towards the potential of extending research to include polygenetic risk scores, which could provide a more nuanced view of genetic influences on social behavior.
“This represents a basic science study into the neurobiological underpinnings of social touch and doesn’t have any direct implications for infants and their families,” Grossmann noted.
The study, “Genetic variability in the oxytocin system is linked to individual differences in cuddliness among human infants“, was authored by Tobias Grossmann and Merle Fairhurst.
