30 Friendship Across the Life Span
somewhat). Other studies found no consistent mean- level changes in average emo-
tional closeness, perceived support, or conflict frequency with friends over 1.5, 4,
or 8 years, and only moderate rank- order stability in these relationship qualities
(Asendorpf & Wilpers, 1998; Neyer & Asendorpf, 2001; Neyer & Lehnart, 2007).
This suggests considerable individual differences in the direction of friendship
change. In other words, the quality of friendships did not change uniformly for
everybody, but for some people friendships’ quality improved, whereas for others
the quality remained stable or worsened. Differences in people’s personality traits
contribute to the explanation of individual differences in qualitative changes of
friends, as addressed in the next section.
In sum, the number of friends increases during young adulthood, and these
increases are partly related to normative life transitions. At the same time, emo-
tional closeness with and support among friends tends to increase most strongly
among single people. When young adults engage in serious romantic relationships
or become parents, the importance and quality of friendships tend to decrease on
average (although some studies also show no meaningful average changes). These
average effects conceal one important methodological drawback: Longitudinal
studies often analyze changes in the average friendship networks, but not specific
friendships. Thus, these studies do not follow specific relationships between per-
son A and friends B, C, and D over time, but examine at later assessment points
that person A now has four friends, which may be friends B, C, E, and F. Hence,
future studies need to carefully track specific friendships to disentangle changes in
the friendship network composition from qualitative changes in specific friendships
(e.g., Wagner, Lüdtke, Roberts, & Trautwein, 2014).
Longitudinal Transactions Between Friendships
and Personality
Not only do personality traits relate to differences in friendships cross- sectionally
(e.g., more extraverted people report more friends) but also, more importantly, per-
sonality and friendships influence each other reciprocally over time. Friendships
presumably are special in their greater susceptibility to personality effects as they
are less regulated by societal restrictions and normative expectations than, for
example, kin relationships.
Personality Effects on Friendship Development
Recent research on longitudinal effects of personality characteristics on the devel-
opment of friendship qualities largely sustained the pattern of cross- sectional
personality– relationship associations reported in the previous sections. For exam-
ple, higher levels of extraversion, agreeableness, and neuroticism each predicted