Distinguished Teaching Professor of Psychology Ganie DeHart has been studying sibling and friend relationships for almost three decades. Nearly 400 students have helped her work on various sibling projects through the years. This fall, some 60 students are conducting research on 11 different projects, six related to the long-term study, four cultural studies and one project on positive social behavior. (Read a story about the research and impact on students.)

By Carol Marcy

Here are some findings from DeHart’s research studies:

 The long-term study that DeHart began in 1992 follows children’s sibling and friend relationships from age 4 through early adulthood. She found that the nature of sibling relationships changes considerably as children grow up.

“For example, the age gap between them becomes less significant,” said DeHart. “The developmental gap between a 2-year-old and a 4-year-old is huge, but it’s less important when they’re 5 and 7, even less so by the time they’re 15 and 17, and pretty much gone by early adulthood.”

Yet, despite the tapering age differences with maturity, DeHart said many pairs of siblings still are quite insistent about who’s older and who’s younger, maintaining that status seems quite important for some kids, especially older siblings.

But as kids grow older, DeHart has found in her research that friend relationships look more like sibling relationships. “The amount of conflict and aggression in friend interactions goes up, but so does the amount of positive social behavior,” said DeHart. “At the same time, conflict and aggression in sibling interactions go down, and positive social behavior increases only slightly.”

DeHart thinks this is because friend relationships become more intimate and familiar over time. “As they get older, friends come to know and understand each other better, which means they know more about how to help each other, but also about how to hurt each other,” said DeHart. “Siblings know all of that much earlier.”

“Friendships also become more enduring, and kids have a clearer sense of how far they can go in behaviors like teasing or disagreeing without endangering the relationship,” said DeHart.

DeHart has also discovered that among those she’s studied, gender differences commonly seen in play with friends are not necessarily there in sibling interactions, especially in aggression and social use of language. “When playing with friends, for example, girls are typically more relationally aggressive than boys are,” said DeHart. “Relational aggression is what people commonly refer to as ‘mean girl’ aggression — behavior that damages relationships or uses relationships to hurt other people, like gossiping, intentional ignoring or social exclusion, and making fun of someone in front of other people. In sibling relationships, boys do it as much as girls do, though they will often try physical aggression first and resort to relational aggression if that doesn’t work — for example, wrestling over a toy and then trying to embarrass their brother in front of a research assistant if they lose the physical battle. With friends, boys also use language more to assert their own goals and less for social affiliation than girls do. With siblings, we don’t find that difference, mostly because girls use much less assertive language with friends than with siblings.”

Cross-Cultural Studies with Siblings

DeHart and her students also have been conducting cross-cultural studies of sibling interactions, which aim to understand behavior that’s influenced by cultural context. They have learned that children in DeHart’s studies from each cultural group have their own distinctive styles of interaction with siblings. “The kids in our Latinx sibling study, for example, had less conflict, aggression, and rough-and-tumble play than the white, western New York kids in our longitudinal study did,” said DeHart.

They have also found that Latina girls in their study were more nurturing toward their younger siblings, especially younger brothers, than girls in the original study were. “We think this is because of cultural differences in how sibling relationships are viewed and what is expected of brothers and sisters,” said DeHart. “These differences in perceptions and expectations of siblings are even clearer in our more recent interview studies of college students from Latinx,Caribbean-American, Chinese-American and African immigrant families, which we’ve been doing in collaboration with Nicholas Palumbo ’14.” Palumbo worked in DeHart’s lab as an undergraduate and is now assistant dean of students for leadership and service at Geneseo and a doctorate candidate in human development at the University of Rochester.

“In white, middle-class American families, sibling relationships are often seen as less important than parent-child relationships,” said DeHart. “There aren’t very clear expectations for sibling behavior or responsibilities toward each other, especially in small families. In the other cultural groups we’ve studied, there tend to be more explicit expectations, roles and responsibilities for siblings, especially older siblings.”