28 CHAPTER ONE
brain development is relevant for understanding the experiences of ado-
lescents. I see the adolescent brain as a phenomenon in Barad’s sense. That
is, it is neither a straightforward empirical reality that is simply observed
and measured by neuroscientists, nor a mere social construction with an
arbitrary relation to reality. Rather, it shows how the assemblage of ideas,
practices, and brain matter can produce a particular neural difference, which
carries material as well as symbolic import.^10
While Males points to poverty as a social factor that is erased in neuro-
biological accounts of adolescent behavior, a number of social neurosci-
entists are trying to identify its impact on developing brains. For example,
Martha Farah and colleagues argue that low ses, a sociological measure of
income, occupational status, and education, which has long been correlated
with poorer academic performance and iq scores, affects particular brain
systems (Farah, Noble et al. 2006; Hackman and Farah 2009; Hackman et
al. 2010; Noble et al. 2005). The suspected mechanisms of low socioeco-
nomic status on neural development include prenatal exposure to drugs
and poor nutrition, lack of cognitive stimulation, exposure to lead and
other toxins, and chronic stress, all of which are thought to disproportion-
ately affect poor people. Farah and colleagues use ses as a proxy for these
collective factors and claim that some “brain systems,” or regions of the
brain that they argue are linked to specific capacities and tasks, are more
susceptible to them than other brain systems.^11 They explain this disparity
as an effect of the earlier maturation of some regions of the brain compared
with others, which renders them less and more vulnerable to environmen-
tal influence. The result, they argue, is a distinctive, consistent neural pat-
tern: “childhood poverty does have reasonably specific neurobio logical
correlates” (Farah, Shera, et al. 2006, 169). This research program, about
which I say more later, defines at- risk populations not through neuro-
biology alone, but by linking patterns of social vulnerability to patterns of
differential vulnerability in the brain.
Stratifying the Adult Brain
The critical windows of developmental plasticity and also their stratifica-
tions by brain region and function exist alongside increasing recognition
that the wiring and morphology of adult brains can be modified. Since the
late 1980s and 1990s, researchers have maintained that the wiring of the