"Of course, such a simple maturational perspective on readiness fails to take into account the
process of development itself. Self-regulation is developing from infancy onward and shaped by
the context in which development is occurring. Variation in self-regulation is present in individual
characteristics and in contextual factors as well as in in the interaction between them (Blair 2014).
At the genetic level (see Figure 1) are individual differences in genes that code for the sensitivity
of neural receptors to catecholamines and glucocorticoids. Variation at this level will influence
physiological, emotional, attentional, and executive control responses to stimulation; individual
differences at each of these levels feed forward to influence activity at higher levels. Increased
emotional reactivity influences the demand on the control of attention, and the control of attention
influences the demand on executive functions. Activity at each level, however, also feeds back
on the level below. Executive functions can help to focus attention, and through attention enable
the regulation of emotion and stress physiology. Through stress physiology, the feedback system
extends to the genetic level to influence gene expression (Meaney 2010, van IJzendoorn et al.
2011)."