Adolescence is the developmental period between childhood and adulthood. It is a unique time characterized by dramatic social transformations (e.g., friendships become more intimate) that occur alongside significant physical, cognitive, and psychological changes.
Adolescence (broadly spanning 10–22 years old) is a unique period in development characterized by rapid and dramatic biological, cognitive, and social changes. For instance, most adolescents go through puberty, which involves hormonal shifts that trigger the development of primary and secondary sex characteristics and physical growth, in addition to changes in emotionality and behavior (e.g., Connolly et al. 1996). The adolescent brain also undergoes important structural and functional changes, including increased synaptic pruning (which contributes to growth in cognitive abilities) and further development of the prefrontal cortex (a brain region implicated in processes such as decision-making and personality expression, e.g., Casey et al. 2008; Steinberg 2010). Both resulting from and amidst these changes, adolescents’ social worlds begin to evolve. For instance, beginning in early adolescence (10–14 years old), youth spend the majority of their waking time with their peers (rather than their families, e.g., Collins and Laursen 2004; Montemayor 1982).
Over the years, adolescents’ peer experiences have garnered significant theoretical and research attention. Often, the focus is on the ways in which peers can cause harm (e.g., vis-à-vis peer pressure and victimization). However, many adolescents form positive and supportive relationships with their peers that foster healthy development and well-being. This entry will explore the unique features of adolescents’ peer experiences, distinguishing between those at the dyadic- (i.e., experiences between two adolescents, such as friendships) and group-level (i.e., experiences involving the larger peer group, such as popularity and peer victimization) of social complexity. Different perspectives on the significance of peers in the lives of adolescents will be offered, including an evolutionary perspective that emphasizes the positive and negative trade-offs (Buss 1995; Hawley 2011).
Beginning with the peer experience of friendship (i.e., voluntary relationships between two same-age peers that are characterized by mutual affection or liking), it is well established that the large majority of adolescents, at any given time point, have at least one mutual friendship as determined by reciprocated friendship nominations (i.e., Zoe nominates Sophia as a friend and Sophia nominates Zoe as a friend; Parker and Asher 1993; Rubin et al. 2015). Most of these adolescent friendships, especially those considered by both adolescents to be a best friendship, are with same-sex peers. In fact, a robust finding in the developmental sciences literatures is that the majority of friendships across the lifespan tend to be with same-sex peers (Hartup and Stevens 1997). This is perhaps best explained by the homophily hypothesis, such that individuals are most attracted to, and subsequently form friendships with, those who are similar in observable characteristics, such as sex, race, and behavior (Kandel 1978). That said, there is a significant increase in the frequency of other-sex friendships throughout the adolescent developmental period (Poulin and Pedersen 2007). In fact, a gradual coming together of boys and girls occurs during adolescence whereby adolescents first develop crushes on and begin to interact with other-sex peers and then later form other-sex friendships and mixed-sex peer groups. This coming together of the sexes, in turn, helps facilitate the formation of adolescents’ first heterosexual romantic relationships, thus beginning the evolutionarily important process of mating.
The features or qualities of friendships also begin to change during the adolescent period. For instance, relative to friendships during childhood, adolescent friendships become more intimate (Buhrmester and Furman 1987). This developmental change is particularly pronounced for girls and is mostly due to adolescents’ engaging in increased levels of intimate disclosure to their friends (i.e., telling each other secrets; Rose and Rudolph 2006). Although friendships become increasingly intimate during adolescence, they also become increasingly characterized by jealousy and other negative relationship processes (i.e., co-rumination or repeated discussion of negative feelings and problems by both relationship partners; Rose 2002), which may explain, in part, why adolescent friendships become particularly vulnerable to conflict and break-up (Benenson and Christakos 2003; Bowker 2011). Indeed, a recent study found that approximately 50% of adolescent friendships dissolve across a single school year (Meter and Card 2016). Thus, many friendships during adolescence would not be considered reliable alliances. And, many adolescents report stress and sadness when their friendships end, likely because many adolescents experience friendship dissolution as a significant interpersonal loss (Bowker 2011). Another rarely discussed reason, however, for the fragility of adolescents’ friendships is that adolescents have greater choice over their peer relationships than they did when they were children, and thus, many may choose to end friendships that are not satisfying, fulfilling, or promoting of resources. In this regard, the self-initiated termination of certain adolescent friendships may be advantageous for individual growth and development, but very little research has evaluated this more positive aspect of friendship dissolution.
Moving beyond the prevalence and characteristics of adolescents’ friendship experiences, friendship is a central construct of study in the adolescent literature because of its influence on adjustment outcomes. In other words, there is a large, ever-growing body of research showing that friendships impact adolescents in numerous and significant ways. For example, adolescents with mutual friends report higher levels of self-esteem and psychological well-being relative to those without mutual friends (for recent review, see Rubin et al. 2015). Importantly, the effects of adolescent friendships on psychological well-being appear to be both immediate and lasting. Bagwell et al. (1998), for instance, found that having a friend in early adolescence predicted positive psychological well-being in young adulthood. These effects were found after controlling for peer acceptance (at the group-level of social complexity, as explained in more detail below), findings consistent with those from many other studies showing that the effects of friendship on psychological and other types of adjustment during adolescence are unique (e.g., Erath et al. 2008). Of course, there is significant variability in the ways in which adolescents’ friendships impact individual adjustment. For example, the characteristics of the friends matter such that adolescents whose friends are suffering psychologically or are delinquent are likely to be negatively influenced by their friends over time through socialization processes (e.g., Poulin et al. 1999; Zalk et al. 2010). From an evolutionary perspective, forming successful friendships (especially with prosocial peers) likely fulfills needs to belong and promotes access to resources (i.e., sources of help and support), above and beyond those available to an individual acting alone, while forming friendships with those in distress interferes with the benefits of friendships (Buss 1995). Finally, it should be acknowledged that individuals of all ages vary in their abilities to form and maintain friendships, and some individuals, including adolescents, find themselves in less desirable and maladaptive friendships because they are rejected, excluded, and victimized by their peers (peer difficulties at the group-level of social complexity, which are described in the following section), and thereby left without any other options.
The Peer Group
Friendships during adolescence are oftentimes embedded in larger peer groups, such as crowds (i.e., large, reputation-based groups such as “populars,” “jocks,” and “brains”; Prinstein and La Greca 2002) and cliques (e.g., smaller groups composed of multiple friendships; Urberg et al. 1995). Crowds and cliques are important to study, as research shows that adolescents are not only influenced by their close friends but also these larger peer group experiences. For instance, Hussong (2002) found that adolescents (aged 16–19 years old) were more likely to use drugs and alcohol if their best friends did, and also if the cliques and crowds with which they affiliated were frequent substance users. In addition, affiliation with highly regarded/valued crowds, such as the “populars” or “jocks,” has been found to promote positive psychological well-being (i.e., high self-esteem, low levels of loneliness) whereas low-status crowd (e.g., “burnouts”) affiliation appears to have the opposite effect (La Greca and Harrison 2005; Prinstein and La Greca 2002). From an evolutionary science perspective such findings are not too surprising, as being a part of a larger group has its advantages (i.e., in terms of resources, protection, etc.), especially a larger group with power (e.g., Buss 1995). Nevertheless, the aforementioned findings nicely illustrate that it is not only friendships that matter during adolescence but larger peer groups do as well.
In addition to cliques and crowds, researchers oftentimes study adolescents’ levels of popularity, rejection, and victimization, all of which reflect how adolescents fare with the larger peer group. Adolescents are uniquely aware of their peers and the social dynamics in their schools, and thus, researchers often ask them to report on who is highly popular, rejected, and victimized in their grade and school. Such procedures (also known as sociometric and peer nomination procedures; see Cillessen 2009) allow researchers to determine who receives the most nominations for these group-level experiences, and from there to understand how variability in such experiences is associated with outcomes such as psychological well-being. For instance, adolescent popularity has garnered considerable theoretical and empirical interest, in part because it peaks in terms of importance during early-to-middle adolescence (LaFontana and Cillessen 2010). Adolescents who are perceived by peers as popular tend to be well-adjusted in a number of ways (e.g., socially skilled, attractive, athletic, Cillessen et al. 2011) and are well-known and highly visible in the larger peer group. As a result, they are oftentimes powerful and influential among peers (Cillessen et al. 2011). Obtaining high levels of popularity is considered adaptive, from an evolutionary perspective, as it increases individual access to or control over tangible, social, and sexual resources. Popular youth, however, often use a combination of aggressive and prosocial (e.g., kind and helpful) strategies to achieve their popularity (Archer and Coyne 2005; also see Resource Control Theory, Hawley 1999); this tendency toward aggression causes them to not always be highly accepted, or well-liked, by peers (Parkhurst and Hopmeyer 1998). Popular youth also commonly achieve high status by engaging in other “norm-violating” behaviors (i.e., substance use, rule-breaking) that can be harmful to their individual development and to their peers but, at the same time, are viewed as cool and mature during adolescence (Cillessen et al. 2011; also see Maturity Gap Hypothesis, Moffitt 1993). As such, there appear to be trade-offs associated with achieving high status among peers during adolescence.
Of course, not all adolescents fare well with their peers, and instead, some adolescents are rejected (i.e., disliked) and victimized by their peers. Adolescents may be rejected if they display traits or behaviors that are not highly valued by the peer group, including shy or withdrawn behavior or aggressive behavior (Parkhurst and Asher 1992); the same adolescents might also be highly victimized by their peers. Other adolescents, however, might be victimized because they are perceived as weak or vulnerable in some way (and therefore, an “easy” target for bullies). For example, adolescents without friends, who appear psychologically distressed, are obese, or have a developmental or learning disability, experience high levels of peer victimization (Hong and Espelage 2012). Victimization takes many forms, including physical (e.g., kicking, hitting, pushing), verbal (e.g., threatening, insulting, name-calling), and relational (e.g., excluding, ignoring, spreading rumors/gossip; Archer and Coyne 2005; Dodge et al. 2006) and can occur in person or online (Salmivalli and Peets 2018). Although bullying and peer victimization are common during childhood, they increase during early adolescence for a number of reasons, including less adult supervision and new links between rule-defying behavior and social status (Cillessen and Mayeux 2004; Moffitt 1993). Not surprisingly, both rejected and victimized youth tend to suffer psychologically (e.g., elevated levels of loneliness, depressive symptoms, anxiety), although some of these negative outcomes may be mollified by protective factors such as having a close friendship (Parker and Asher 1993). Beyond mental health outcomes, peer victimization and rejection have also been found to negatively impact physical health (e.g., dysregulated cortisol responses) and to interfere with academic functioning (e.g., Erath et al. 2008; McDougall and Vaillancourt 2015). As such, over the past few decades there has been widespread interest in prevention and intervention efforts targeting peer rejection and victimization, many of which are school-based and call on peers to assist and intervene (e.g., Yeager et al. 2015). However, such programs, especially those focused on peer victimization and those in the United States, have been limited in effectiveness, in part because many adolescents are reticent to protect their peers out of fears for becoming targets themselves (Salmivalli and Peets 2018). Thus, negative group-level peer experiences continue to be a serious concern during adolescence.
Despite seemingly obvious applications of evolutionary science to understanding adolescent issues, developmental psychologists have been slow to adopt this framework. Just a few years ago, one prominent psychologist observed: “…at the time of this writing, Google Scholar located only four articles with the word ‘evolution’ or ‘evolutionary’ in the title from all the English language journals on adolescence. This gap is extraordinary in light of the reproductive maturity of the average 15-year-old and evolutionists’ interest in reproduction” (Hawley 2011, p. 307). For the most part, developmental research on adolescent issues has taken a risk-based approach focused on elucidating when and why problems occur (e.g., how behaviors such as aggression contribute to peer and psychological problems). Evolutionary scientists, however, have cautioned against the tendency to strictly pathologize adolescent “problem” behaviors (e.g., aggression/bullying, substance use, sexual activity) and instead have suggested a more balanced perspective that allows for the possibility of both positive and negative trade-offs for any behavior. In addition, it has been suggested that many “problem” behaviors during adolescence occur because they are high risk/high reward. For example, substance use can be considered risky as it could lead to detrimental or even fatal outcomes, but, it can also be viewed as potentially adaptive/rewarding by fostering improved group standing and belongingness (Ellis et al. 2012). As such, drawing upon an evolutionary science perspective could enrich the study and understanding of adolescent development by focusing on such trade-offs.
Beyond striving for better integration of evolutionary and developmental sciences, there is still much to be learned about the varied issues pertaining to adolescent development, only a small subset of which were discussed in this entry. For instance, many issues related to adolescence are changing with the proliferation of technology, and researchers have been slow to catch up. In the future, there will be a great need to better understand the ways that social media has impacted adolescents’ social worlds, including problems with peers (e.g., cyberbullying, peer exposure and influence; Hawley 2011), and also potential benefits (e.g., reduced loneliness, the facilitation of intimacy between friends). Furthermore, given our increasingly connected world, cross-cultural variations and similarities in adolescent development and peer experiences are imperative to better understand and could lead to an deeper knowledge of which aspects of adolescent development are universal (and thus biologically or evolutionarily based) versus context-bound. In addition to cultural differences, it is also important to consider that many individual-level differences (e.g., in personality and other traits) may impact or alter the types of friendships and group-level experiences adolescents have. For example, there is a growing literature revealing variability in the reasons that some adolescents choose to withdraw or keep away from their peers (e.g., shyness versus preferences for solitude), and how these differences impact how they are perceived by peers and their psychological well-being (see Rubin et al. 2009). Finally, more multidisciplinary research that cuts across disciplines is needed to fully understand the complex ways that adolescents’ social, biological, and cognitive functioning interact to predict short- and long-term outcomes.
- Cillessen, A. H. N. (2009). Sociometric methods. In K. H. Rubin, W. M. Bukowski, & B. Laursen (Eds.), Handbook of peer interactions, relationships, and groups (pp. 82–99). New York: Guilford.Google Scholar
- Cillessen, A. N., Schwartz, D., & Mayeux, L. (2011). Popularity in the peer system. New York: Guilford.Google Scholar
- Connolly, S. D., Paikoff, R. L., & Buchanan, C. M. (1996). Puberty: The interplay of biological and psychosocial processes in adolescence. In G. R. Adams, R. Montemayor, T. P. Gullotta, G. R. Adams, R. Montemayor, & T. P. Gullotta (Eds.), Psychosocial development during adolescence (pp. 259–299). Thousand Oaks: Sage.Google Scholar
- Dodge, K., Coie, J., & Lynam, D. (2006). Aggression and antisocial behavior in youth. In Handbook of child psychology: Vol. 3, Social, emotional, and personality development (6th ed., pp. 719–788). Hoboken: Wiley.Google Scholar
- Ellis, B. J., Del Giudice, M., Dishion, T. J., Figueredo, A. J., Gray, P., Griskevicius, V., … Wilson, D. S. (2012). The evolutionary basis of risky adolescent behavior: Implications for science, policy, and practice. Developmental Psychology, 48, 598.Google Scholar
- Poulin, F., Dishion, T. J., & Haas, E. (1999). The peer influence paradox: Friendship quality and deviancy training within male adolescent friendships. Merrill-Palmer Quarterly, 45, 42–61.Google Scholar
- Rubin, K. H., Bukowski, W. M., & Bowker, J. C. (2015). Children in peer groups. In M. H. Bornstein, T. Leventhal, R. M. Lerner, M. H. Bornstein, T. Leventhal, R. M. Lerner (Eds.), Handbook of child psychology and developmental science: Ecological settings and processes (pp. 175–222). Hoboken, NJ, US: John Wiley & Sons Inc.Google Scholar
- Salmivalli, C., & Peets, K. (2018). Bullying and victimization. In W. M. Bukowski, B. Laursen, K. H. Rubin, W. M. Bukowski, B. Laursen, & K. H. Rubin (Eds.), Handbook of peer interactions, relationships, and groups (pp. 302–321). New York: Guilford.Google Scholar