. .[They] correctly understand . . . that socialization is the most. . .morally important thing they will do in high school" (Brooks 2001:74-75, cited in lecture notes). Socialization requires adaptability and flexibility, which temperamentally-sensitive individuals lack and can make them more vulnerable to the stressors that all adolescents endure. Perhaps equally significantly, high-reactive adolescents recognized their challenges and rated themselves as more dour and serious than their peers who rated themselves as high on optimism. The biological tendency, once socially reinforced, became a kind of self-fulfilling prophesy for the high-reactive teens (Kagan 2010: 38). Biological propensities to stress can be measured in both qualitative and quantitative ways. Quantitatively, brain scans subjects can demonstrate whether the regions of the brain associated with anxiety such as the amygdala, fire up when stimulated and the results can be compared between low-reactive and high-reactive subjects. Interviews, questionnaires, and self-perceptions of teens can also be assessed on a qualitative level. Comparing the anecdotal evidence of individuals who report high levels of anxiety and those who do not in terms of the reactivity of their brain enables scientists to demonstrate the clear impact of the physical structures of the brain on behavior, and also to analyze how there is interaction between the brain and development. Certain types of brains seem to have a greater propensity to 'fire off' anxiety-producing reactions than other brains, even when both are subjected to the same stimuli.

This example shows once again the complex interaction between nature and nurture. All human beings are subject to stressors simply by virtue of being human. The brain's structure propensity to react, depending on genetics and also the early environment of the developing child can create an adolescent who is more or less likely to react to stress in a particular fashion. Once patterns of reaction have been established, these habits become more and more difficult to break as they become ingrained responses within the individual's character (Kagan 2010: 42-43).

Anxiety can give rise to a host of different reactions, such as timidity, uncertainty of what behavior to display, and other behaviors which can increase the propensity of the adolescent to be rejected. Rejection sensitivity can actually create...

Vulnerable children may become more vulnerable adolescents, given the nature of this developmental stage where rejection -- by certain peer groups, teachers, romantic partners, even colleges -- is inevitable (Kagan 2010: 43). Contrary to what the pure 'nature' enthusiasts used to espouse, namely that past history alone affected current behavior -- 'I am neurotic because my girlfriend dumped me' -- current research suggests that a highly sensitive teen will brood over and internalize the sadness and rejection generated by a breakup that another adolescent might simply ignore. This concept is supported by research which demonstrates that adolescents who are high-reactive show more responsiveness to human faces than low-reactive adolescence. In other words, a frown that might produce only a mild reaction in a low-reactive individual might produce a fairy extreme reaction in a high-reactive individual.
All human beings are motivated by similar drives in adolescence, at least within our particular, Western cultural context. "In our culture, to make it to high school in middle/late adolescence is sign of resilience: the individual needs to have had enough social capital to get through the snark-infested hallways and the locker rooms of middle school. In this stage, bodies get where they were going, yet the allure of the crowd becomes more enticing. High school is the stage in which the dramas of life are made real" (Lecture notes 2011). This portrayal of adolescence suggests there may even be a degree of higher reactivity and difficulty in interpreting emotional signals amongst adolescents, in a manner that is not present in adults with developed, mature brains. But just like all adolescent bodies are not created equal, not all adolescent brains will respond in the same way to their environments. Their level of responsiveness will affect not simply the adolescents but also the adults they become.