“…Compared to tonic cardiac vagal activity, relatively little is known about the role of phasic cardiac activity in the context of selfregulation (Butler, Wilhelm, & Gross, 2006;Ingjaldsson, Laberg, & Thayer, 2003;Segerstrom & Nes, 2007;Smith et al, 2011). Reduced phasic cardiac activity, or vagal suppression, has long been construed as an autonomic response to stress (Beauchaine, Gatzke-Kopp, & Mead, 2007;Beauchaine, Katkin, Strassberg, & Snarr, 2001;El-Sheikh, Hinnant, & Erath, 2011;Schwerdtfeger & Derakhshan, 2010). When people are directly exposed to a stressor, such as a video clip depicting an escalating conflict between peers (Beauchaine et al, 2001(Beauchaine et al, , 2007El-Sheikh et al, 2011), performing a difficult mental stress task (Weber et al, 2010), or engaging in a reaction time shock avoidance task in which a shock is threatened as a penalty for slow performance (Uijtdehaage & Thayer, 2000), phasic HRV suppression occurs.…”