Older sisters and younger brothers: The impact of siblings on preference for competition

• The impact of siblings on one’s personality has been long argued in psychology.
• One of the core issues is who rates the participants’ personality traits.
• We go beyond past studies by obtaining competitive trait in economics experiment.
• Having older sisters is negatively associated with men’s competitive preferences.
• Our results support sibling hypotheses from the viewpoint of economics experiment.

Psychology studies have long argued the possibility that sibling structure, such as birth order and the sex of siblings, shapes one’s personality traits. One of the core issues involved is that of who rates subjects’ personality traits in studies. The present studies (N = 135 in Study 1, N = 232 in Study 2) surpassed the examinations performed in previous studies by obtaining information regarding one of the key personality traits, preference for competition, using a framework developed via experimental economics rather than subjective ratings. Despite the fact that the two studies involved different types of task, we consistently observed that older sisters exerted a significant impact on their younger siblings in both studies. In particular, having an older sister was negatively associated with men’s competitive preferences. We also obtained suggestive evidence that having an older sister was positively associated with women’s competitive preferences. Our results support sibling hypotheses from the perspective of experimental economics.