We are all confronted almost daily with a major source of interindividual variation – people of the same chronological age vary tremendously in physical attributes and behaviors. Some look younger (and consequently may feel younger) than their age would predict, whereas others look older (and may disregard this entirely). A particularly impressive case of variation occurs during puberty: whereas some early adolescents appear physically almost fully grown, others still remind one of a child, and yet both may attend the same classroom and share the same chronological age. In the many domains of everyday interactions we adapt our behavior to the perceived age of others, our expectations and behavioral overtures toward young people may be inadequate; either we treat them like grown-ups (thus overtaxing capabilities) or like children (thereby underestimating potential). At any rate, it is likely that such behaviors, if persistent, could lead to age-inappropriate changes in the behavior of the young. Social reactions to physical maturation also vary widely across cultures. The onset of puberty in girls is universally followed by more restrictions than is observed for boys. Girls are subjected to menstrual taboos, dress codes, and limitations of their activities, whereas boys usually do not have to deal with increased supervision and limitations of their freedom (Petersen, Silbereisen, and Sörensen, 1996).

This chapter deals with interindividual variation in the timing of puberty and its association with differences in psychosocial functioning; as will be seen, this relationship is complex and goes well beyond the role of the social processes just mentioned.