Economist Joseph Hotz theorizes that parents subconsciously enforce stricter rules on their firstborn as an efficiency play. By maximizing the oldest child's success, they create a role model whose achievements and behaviors will 'spill over' to younger siblings, maximizing the return on total parental investment.
The home should be a sanctuary of warmth and nurturing. Hard-driving discipline and skill-building criticism are often more effectively delivered by external figures like coaches or teachers. This strategy preserves the positive parent-child relationship while still allowing children to develop resilience and grit in structured settings.
Parents obsess over choices affecting long-term success, but research suggests these have minimal effect on outcomes like personality. Instead, parenting profoundly shapes a child's day-to-day happiness and feelings of security, which are valuable in themselves and should be the primary focus.
To avoid direct competition and establish a unique identity, siblings often subconsciously pursue excellence in different domains. If one child dominates academics, another may pivot to athletics or arts, even if they have overlapping talents. This evolutionary strategy, called "niche picking," fosters individual success.
A study by sociologist Emma Zhang found an older sibling's arbitrary academic advantage (from being old for their grade) boosts the younger sibling's performance. This demonstrates a powerful non-genetic, non-parental mechanism through which family-level advantages compound and perpetuate broader societal inequality.
Countering the idea that parenting has little effect on outcomes, a twin study found that the twin receiving slightly more maternal affection between ages 5-10 grew up to be more open, conscientious, and agreeable. This suggests that small, differential parenting choices have measurable long-term consequences for personality.
Parenting isn't a one-way street. A child's inherent temperament (e.g., ADHD, agreeableness) actively shapes parental reactions. This creates powerful feedback loops where, for instance, a difficult child elicits stricter parenting, which in turn affects development. The outcome is often misattributed solely to the parenting style.