A recent study suggests that middle children and individuals from larger families exhibit traits of agreeableness, honesty, and humility compared to their siblings.

The findings challenge existing research on birth order and personality dynamics.

Contradictory Stereotypes

Common stereotypes attribute specific personality traits to individuals based on their birth order, such as ambitious firstborns, peace-making middle-borns, or indulged youngest siblings. However, past research has failed to consistently support these generalizations. Previous studies have produced conflicting results due to small, non-representative samples.

Previous Research

In 2015, two substantial studies involving thousands of participants aimed to investigate the relationship between birth order and personality using the Big Five model. The Big Five dimensions encompass extraversion/introversion, agreeableness, openness to experience, neuroticism, and conscientiousness.

Neither study presented strong evidence linking birth order to personality traits. While a minimal association with intelligence was observed among older siblings in the Project Talent study, the practical impact on predicting intelligence was limited.

New Findings

A recent study published in PNAS introduced a distinct personality assessment tool called HEXACO to explore personality differences linked to birth order and family size. The HEXACO model includes honesty/humility, emotionality, extraversion, agreeableness, conscientiousness, and openness to experience.

Unlike the Big Five model, HEXACO's definition of agreeableness emphasizes adaptability, graciousness, and forgiveness. This study highlights variations in personality traits among individuals, emphasizing the impact of family size on these characteristics.

Faculty Experts: Catherine Salmon-The psychology of middle children and birth order

University of Redlands