Grad student studies rivalry among siblings

 

Is sibling rivalry a behavior that has evolved over time? Some scientists think so. And they’ve found that some evolved behaviors are motivated by lack of – and competition for – resources.

 

 

Michelle Dillon, who is completing her master’s degree in anthropology, is taking the next step in putting these two ideas together. She is doing research in a rural village on the Caribbean island of Dominica on the hypothesis that resource competition motivates sibling rivalry.

 

Results largely are confirming her hypothesis.

 

“Children are very savvy to the effects of siblings on resource distribution and will become aggressive as a result of these competitors for resources,” she said.

 

The results also have prompted more questions, which Dillon hopes to answer as she continues her education and pursues her Ph.D. at WSU.

 

To conduct her studies, Dillon interviewed mothers in a rural village in Dominica about their families and perceptions of sibling rivalry. She plans to continue her work with more interviews as well as observation of sibling and family interactions.

 

She hypothesized that certain variables would make families fight more because of scarcity of resources to share. Some findings confirmed this hypothesis:

 

• Larger families fought more
• A father’s involvement and investment, which increased resources in the family, decreased sibling rivalry
• Lastborn children, who get what’s left of resources spread throughout the family, fought more
• Middle children, who never get their own time of undiluted parental investment as do firstborns and lastborns, fought more with non-middle children

 

Other findings did not confirm Dillon’s hypothesis:

 

• The presence of “alloparents,” relatives who help with the family and thus increase resources, did not decrease sibling rivalry
• Same-sex siblings, who should need more similar resources, did not fight more than mixed-sex siblings

 

And other findings varied depending on whether variables were applied to entire families or to two particular children within a family:

 

• Families with half-siblings (less related so they should be less inclined to cooperate since their genes won’t be as represented in each other’s offspring) fought more. But – when studied two children at a time – it was full siblings who fought more with each other
• Pairs of children closer in age, who should compete more for similar resources, fought more. But families with closer-spaced children did not fight more

 

“This research was a good foundation for future inquiries,” Dillon said. “My next steps will be to conduct interviews with better measures of alloparenting and paternal investment and to directly observe circumstances surrounding sibling rivalry.”

 

Among the specific areas she wants to investigate:

 

• Differences if alloparents are from the mother’s or father’s family
• How the type of mother-father relationship (visiting, living together or marriage) influences resources provided by the father
• Whether age and sex affect the children’s style of fighting and resources over which they fight