In childhood, the understanding of friendship centers on common activities, physical proximity, and shared expectations. These friendships offer opportunities for play and practicing self-regulation, with children more likely to share with those they consider friends. Young children infer friendship through cues like sharing resources and secrets. As they mature, children become more reliant on others, develop empathy, enjoy group play, and experience peer rejection. Establishing good friendships early on aids in later societal acclimation. Reports indicate that 75% of preschool children have at least one friend, rising to 78% by the fifth grade, with 55% having a mutual best friend. Approximately 15% of children are chronically friendless. Childhood friendships contribute to developing empathy and problem-solving skills. Parental coaching, focusing on openness, similarity, and shared fun, can assist children in forming friendships.
Adolescence sees friendships become more giving, frank, supportive, and spontaneous. Adolescents seek reciprocal relationships and avoid peers exhibiting problematic behavior. Friendships during this period are more heavily based on similar morals, values, loyalty, and shared interests, compared to childhood friendships which often stem from proximity and shared playthings. A study of American adolescents found that those less likely to engage in problematic behavior had friends who performed well in school, participated in school activities, avoided drinking, and had good mental health. The reverse was true for adolescents who did engage in problematic behavior. The influence of friends on problematic behavior depended on exposure and group integration at school. Friendships formed during post-secondary education tend to be more enduring. Cross-racial friendships are less common in late adolescence, likely due to prejudice and cultural differences.
In adulthood, friendships provide companionship, affection, and emotional support, positively impacting mental well-being and physical health. Maintaining meaningful friendships in the workplace can be challenging due to competition and a transactional feel. A 2023 Pew Research Center survey indicated that 8% of respondents had no close friends, and an additional 7% had only one. The surveyed 2,000 American adults reported an average of two close friends, defined as individuals with whom they had discussed important matters in the past six months. Numerous studies suggest that friendships enhance self-esteem.
Older adults report high personal satisfaction in their friendships, even as the overall number of friends tends to decline. This satisfaction is linked to an increased ability to perform daily activities, reduced cognitive decline, fewer hospitalizations, and better rehabilitation outcomes. The decline in friend numbers in later life may be influenced by factors like lucidity, speech and vision capabilities, and marital status. Carstensen's Socioemotional Selectivity Theory explains this phenomenon by suggesting a shift in motivation from information-gathering to emotional regulation, leading older adults to prioritize relationships with those with whom they share an emotional bond to maintain positive emotions. Research consistently shows that older adults with the highest levels of happiness and well-being also report strong, close ties to numerous friends. As family responsibilities and vocational pressures lessen, friendships become more crucial, providing links to the community, acting as a buffer against depression and loneliness, and compensating for potential losses in family support. For those with limited mobility, interactions with friends facilitate continued societal engagement. Older adults in declining health who maintain contact with friends demonstrate improved psychological well-being.
Forming and maintaining friendships requires time and effort, with initial interactions potentially taking 20 to 60 hours in the first weeks, and close friendships requiring over a hundred hours. Friendships are primarily formed by choice, based on mutual admiration, commonalities, and enjoyment of socializing. Given the mental, social, and health benefits of friendships, individuals tend to seek out people who offer these advantages. Recent research highlights differences in friendship preferences between men and women. While both genders prioritize traits like being prioritized over other friends and having friends with varied knowledge, women tend to prefer emotional support, disclosure, and reassurance more than men. Conversely, men show a greater preference for friends who offer opportunities for status accrual, reputation enhancement, and physical aid. Many people underestimate how much others like them, a phenomenon known as the "liking gap," which can hinder friendship formation.
According to communications professor Jeffery Hall, most friendships involve tacitly agreed-upon expectations in six areas: positive regard, self-disclosure, instrumental aid, similarity, enjoyment, and agency. Not all relationships balance these areas equally; for instance, women may favor friendships emphasizing positive regard and self-disclosure, while men might lean towards those with more agency.
Individuals with certain developmental disorders, such as attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, or Down syndrome, may face challenges in making and maintaining friendships.
Friendships can end due to natural changes over time, leading to emotional and physical distance, or due to sudden events, like discovering incompatible values. The dissolution of a friendship can be perceived as a personal rejection, leading to guilt, anger, and depression, particularly in childhood. However, the negative impact can be mitigated by forming new close relationships.
Friends often share similarities in age, gender, behavior, substance abuse, personal disposition, and academic performance.
Female bonding typically focuses on interpersonal connections and mutual support, with women being more expressive in their same-sex friendships, though they may also experience more anxiety, jealousy, and relational victimization. Male bonding can be more centered on social status, potentially discouraging emotional expression, and men are more likely to define friendships through shared physical experiences, reporting higher levels of physical violence in their friendships. Male-male friendships often resemble alliances, while female-female friendships are more attachment-based, leading to less emotional upset upon their dissolution. Older men may rely on female companions to compensate for a comparative lack of social capital. Studies suggest women are slightly more likely than men to self-report having a best friend. The preference for same-sex friendships over cross-sex friendships is termed homosociality or gender homophily.
Cross-sex friendships, defined as non-intimate friendships between men and women, are also described as heterosociality or gender heterophily. These friendships have a more recent history, becoming widely accepted in the 20th century. The prevalence of cross-sex friendships relative to same-sex friendships varies by country, and sex segregation can impede their formation.
The definition of a true friend versus an acquaintance or co-worker varies across cultures. In English-speaking cultures, weaker relationships are often included as friends, whereas in cultures like Russian and Polish, only the most significant relationships are considered friends. Western cultures often view friendships as secondary to familial or romantic relationships. In Ancient Greece, friendships were more utilitarian and based on obligation and reliance, though conceptions varied, and the Greeks held a broader understanding of friendship than modern English-speaking cultures. Aristotle identified three types of friendships: those based on pleasure, advantage, and virtue. Chinese respondents in one study reported more friendship taboos than their British counterparts. In ethnically diverse countries, children and adolescents tend to form friendships with others of the same race or ethnicity from preschool onwards, peaking in middle or late childhood.
Evolutionary approaches to friendship focus on its function, exploring how it benefits individuals psychologically and influences behavior. The theory of Reciprocal Altruism suggests that friendship allows for the exchange of benefits between unrelated individuals, with mechanisms to track these exchanges and avoid poor cooperators. Another perspective views friendships as insurance investments, where individuals assess a potential friend's willingness and ability to reciprocate, and the overall worth of the friendship. The Alliance Hypothesis posits that friendships serve to acquire alliances for future conflicts, with individuals aiming to recruit more allies than their competitors. The relative rank of potential allies is considered a key factor in deciding loyalty.
Studies indicate that strong social supports improve health prospects and longevity. Conversely, loneliness and a lack of social support are linked to increased risks of heart disease, viral infections, cancer, and higher mortality rates. Researchers have referred to friendship networks as a "behavioral vaccine" that enhances both physical and mental health. While a significant body of research links friendship and health, the precise causal mechanisms remain unclear. Most studies are prospective, observing correlations rather than definitive cause-and-effect relationships. Theories suggest that friends encourage healthier lifestyles, prompt seeking of help when needed, enhance coping skills for illness, and may even affect physiological pathways protective of health.
A lack of friends is common among individuals diagnosed with various mental disorders. A 2004 study in the American Journal of Public Health found that a lack of friendship increases the risk of suicidal ideation in female adolescents, particularly when their friends are not friends with each other, though a similar effect was not observed in males. Higher friendship quality directly contributes to self-esteem, self-confidence, and social development. Research from the World Happiness Database indicates that people with close friendships are happier, irrespective of the absolute number of friends. High-quality friendships may protect children against developing anxiety and depression. Conversely, having few friends is associated with school dropout, aggression, adult crime, and loneliness. Peer rejection is linked to lower later workforce aspirations and social participation, while higher levels of friendship correlate with higher adult self-esteem.
Having more close friends is associated with improved mental health and cognitive ability, but this association plateaus around five friends, after which having more friends is not linked to better mental health and may correlate with lower cognition. Additionally, individuals with very few or very many friends exhibited more symptoms of ADHD and were less able to learn from their experiences.
Jealousy, often studied in romantic contexts, can also arise in friendships when there is a perceived threat to a valued relationship. Friendship jealousy acts as a signal that another person may be a threat to one's relationship with a close friend, motivating behaviors to prevent further development of that other relationship. Research indicates that friendship jealousy is triggered by the potential loss of a friend, is highly sensitive to feelings of being replaced, and intensifies with the closeness and value of the friendship. Women, compared to men, tend to express more jealousy over the potential loss of a best friend to another woman.
Friendship is observed in highly intelligent animals, including higher mammals and some birds. Comparative animal research suggests the existence of friendships or similar relationships in animals, primarily serving to form and solidify alliances for fitness and survival. These alliances are formed for protection, competition for reproductive access, social comfort, solidifying social bonds, and disease avoidance. A meta-analysis of grooming behaviors in 14 primate species found that grooming elicits benefit exchanges, such as support in future intra-species conflicts. Male bottlenose dolphins use synchronous surfacing to identify potential male allies, while female bottlenose dolphins use gentle contact behaviors in response to male harassment. Female spotted hyenas form alliances to improve their dominance rank. Feral female horses develop alliances with other females to avoid harassment from males, increasing their offspring's survival chances.