“…By contrast, low resting vagal tone has been related to frustration and distress in infants (Calkins & Fox, 1992;Stifter & Fox, 1990) and toddlers (Porges, Doussard-Roosevelt, Portales, & Suess, 1994). Low vagal tone has also been linked to deficits in emotion regulation skills in healthy pre-school (Calkins, 1997;Cole, Zahn-Waxler, Fox, Usher, & Welsh, 1996;Santucci et al, 2008) and school-age (Eisenberg et al, 1996;Jemerin & Boyce, 1990) children. Similarly, poor vagal regulation of cardiac function has been related to lower peer status (Graziano, Keane, & Calkins, 2007) and increased social withdrawal (Kagan, Reznick, & Snidman, 1988) in young children.…”