“…Social inhibition also reflects an underlying trait that exists along a continuum, ranging from low to high social inhibition (Schneier, Blanco, Antia, & Liebowitz, 2002; Stein, Walker, & Forde, 1994). Social inhibition is a fundamental behavior that is heritable (Eley et al, 2003; Emde et al, 1992; Robinson, Reznick, Kagan, & Corley, 1992; Schwartz et al, 2003b), present early in development (Kagan, Snidman, & Arcus, 1998b), and observable across species (Clinton, Stead, Miller, Watson, & Akil, 2011; Fox, Shelton, Oakes, Davidson, &Kalin, 2008; Gosling, 2001; Qi et al, 2010). Social inhibition is assumed to have a biological basis; inhibited children display a pattern of physiological hyperarousal including a high and stable heart rate (Kagan, Reznick, & Snidman, 1998a) and elevated cortisol levels (Kagan et al, 1998a).…”