Why Sisters Fight

Source: Sam Wordley/Shutterstock

Siblings are often with us from birth or early childhood and sibling relationships can be some of the most important relationships in our lives. But while brothers and sisters can be great sources of cooperation, friendship, and support, conflicts between siblings are also common. What factors influence sibling conflict and sibling cooperation? And which type of siblings do show more conflicts, brothers or sisters?

A new study sheds light on sibling relationships

A new study, just published in the journal Evolutionary Psychological Science (Salmon and Hehman, 2021), was aimed at answering these questions. In the study, researchers Catherine A. Salmon and Jessica A. Hehman of the University of Redlands asked 364 young adults (262 women and 102 men) aged 17 to 30 about their relationships with their siblings. The volunteers reported on 573 siblings.

The following factors were assessed:

• Was the volunteer male or female?
• Was the sibling male or female?
• Birth interval: How large was the absolute age difference between the volunteer and their sibling?
• Co-residence: Whether or not the volunteer and their sibling lived together and from which age to which age?
• Relatedness: Were the volunteer and their siblings' full-siblings or half-siblings?

The scientists assessed sibling conflict by using the Sibling Issues Checklist, a questionnaire that includes a list of 20 potential sibling conflict issues. These 20 questions are divided into two major categories:

• Conflict over equality and fairness. This category includes questions about conflicts over parents’ attention and whose turn it is to do chores, among others.
• Conflict over the invasion of personal and psychological space. This category includes telling the sibling what to do and borrowing things without permission, among others.

The scientists also assessed sibling cooperation using the Prosocialness Scale for Adults, a questionnaire that includes a list of 16 statements on common situations that involve sharing, helping, and other prosocial behaviors.

The results

The study had several interesting findings.

Conflicts between siblings were predicted by gender of the subject, gender of the sibling, birth interval, duration of co-residence, and the degree of relatedness. A greater level of conflict was experienced by same-gender siblings, especially sisters; siblings close in age; siblings who have lived together longer; and full-siblings compared to half-siblings.

Prosocial behavior between siblings was only predicted by gender of the volunteer and relatedness, with women and full siblings reporting more prosocial behavior. This pattern of results suggests that sibling conflict and sibling cooperation may be somewhat independent of each other, as they are shaped by different sets of factors.

Conclusion

To answer the question from the beginning: The study suggests that sisters have more sibling conflicts than brothers, especially if they are full-siblings that are close in age and live together for a longer period of time. The scientists point out that full siblings, siblings that are close in age, and siblings that live together (e.g., while growing up in their parents’ house) all compete for the same limited resources, such as parents’ attention, explaining this pattern of results. It was also notable that women showed both more prosocial behavior toward their siblings (independent of whether they were brothers and sisters) and more conflict with their sisters, but not brothers. The researchers pointed out that their findings are in line with previous research suggesting a greater emotional closeness to a sibling coming from a sister than coming from a brother. This could partly explain the higher amount of both negative emotions (conflicts) and positive emotions (cooperation) toward siblings experienced by female volunteers in the study.

Facebook image: Sam Wordley/Shutterstock