Personality differences between birth order categories and across sibship sizes

• 成果类型: Article
• 署名作者: Ashton, Michael C.; Lee, Kibeom
• 署名单位: Brock University; University of Calgary
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14479
• DOI: 10.1073/pnas.2416709121
• 发表日期: 2025-12-30

摘要

We examined associations of self- reports on the HEXACO Personality Inventory-Revised (HEXACO-PI-R) with birth order category and sibship size, controlling for participant sex and age. In a first sample (N > 700,000 online adults, mainly from English- speaking countries), Honesty- Humility and Agreeableness both showed the highest means for middle-borns, followed in order by last-borns (youngests), firstborns (oldests), and only children, with differences between middles and onlys of d >= 0.20. The same result was replicated in a similar but smaller second sample (N > 70,000) in which sibship size was also assessed, thereby allowing birth order differences to be separated from sibship size differences. In that sample, Honesty- Humility and Agreeableness showed higher means with larger sibship sizes, with differences between sibship sizes of 1 and 6+ of d = 0.30 and d = 0.36, respectively. Controls for upbringing religiousness and current religiousness reduced these differences by about 25%. Within sibship sizes, birth order differences in these dimensions were considerably smaller but oldests remained up to d = 0.10 lower than middles and youngests. Openness was d approximate to 0.10 higher for onlys than for non-onlys collectively, and within sibship sizes, Openness was d approximate to 0.10 higher for oldests than for middles and youngests.