Short answers, pulled from the story.
A survey of 2,000 American adults found that the average person had two close friends, defined as people they had discussed important matters with in the past six months. A 2023 Pew Research Center survey found that 8% of respondents reported having no close friends at all.
Research indicates it takes around 20 to 60 hours of interaction in the first weeks after meeting someone to establish a basic friendship. Forming a close friendship can take more than a hundred hours of shared time.
Based on reports from teachers and mothers, 75% of preschool children had at least one friend. That figure rose to 78% by the fifth grade, while about 15% of children were found to be chronically friendless for periods of at least six months.
Aristotle identified three kinds of friendship: those grounded in pleasure, those grounded in advantage, and those grounded in virtue. Greek friendships of the Classical era were also noted as more utilitarian than affectionate, based on obligation and reliance.
Researchers have described friendship networks as a "behavioral vaccine" that boosts both physical and mental health. Strong social supports are linked to better health and longevity, while loneliness and lack of social support are associated with higher risks of heart disease, viral infections, cancer, and higher mortality rates overall.
The Alliance Hypothesis argues that the primary function of friendship is to build alliances for future conflicts. It holds that conflicts are typically won by the side that recruits more allies, so individuals benefit from forming friendships with people who rank highly among their peers and are likely to provide loyal support in future disputes.