The chronological order of sibling birth in a family.

Alfred Adler was a pioneer in the study of birth order, suggesting that social relationships, especially among siblings and between children and parents, significantly impacted the growth and personality of children. Today, birth order research focuses on five ordinal birth positions: first-born, second-born, middle, last, and only-children. Anecdotally, much has been made about the effect of birth order on personality and intelligence, and scientific studies seem to support some notions about birth order and certain personality traits. For example, studies have consistently linked first-born children with higher academic achievement when compared to later-born children. In general, first-born children have been found to be responsible, assertive, and task-oriented, often rising to leadership positions as adults. Second-borns and middle children report feeling inferior to older children because they do not possess the older child's advanced abilities. Often, they will...