Infants' and mothers' vagal reactivity in response to anger.

Anger between adults is associated with greater physiological arousal and less effective vagal regulation in children (e.g., Ballard, Cummings, & Larkin, 1993; El-Sheikh, Ballard, & Cummings, 1994; El-Sheikh, Cummings, & Goetsch, 1989). On the other hand, effective vagal regulation buffers children from negative behavioral outcomes associated with inter-adult anger (El-Sheikh, Harger, & Whitson, 2001; Katz & Gottman, 1995). Because anger in the family is a risk factor for behavior disorders characterized by dysregulation of anger in childhood and adolescence and because ineffective vagal regulation is a consistent biological marker for these disorders (Beauchaine, Gatzke-Kopp, & Mead, 2007), it is critical to understand the impact of inter-adult anger on emerging systems of vagal regulation. Examining these processes during infancy is particularly important, as emotionally challenging environments can have a significant effect on biological regulatory systems as they undergo rapid development early in life (Pollack, 2005). How anger between adults influences development of vagal regulation is unknown. One theory is that exposure to anger sensitizes developing regulatory systems, making children hyper-reactive initially and eventually leading to less reactive and less effective regulation through regulatory “burn-out.” Another is that spillover of parent conflict diminishes effective parenting support for infants’ regulation (e.g., Davies & Cummings, 2006) by affecting parents’ own regulation of emotion. The first step in studying these theories is to understand the direct effects of exposure to anger on infants’ and mothers’ vagal regulation. The current study was designed to do this by observing their RSA reactivity, i.e., change in RSA from baseline, during an experimental emotion exposure task (EE) and a subsequent parent-infant interaction task, the Still-Face Paradigm (SFP; Tronick, Als, Adamson, Wise, & Brazelton, 1978). For infants, observing RSA reactivity in a challenge task (mother’s still-face) after anger exposure afforded the opportunity to assess whether anger exposure could sensitize infants to stress in the short-term. Observing mothers’ RSA reactivity in the two tasks afforded the opportunity to assess whether RSA reactivity to anger exposure would carry over into mother-infant interaction. RSA reactivity was assessed because it is a purported index of physiological regulation of emotion, behavior, and attention, particularly in social interaction (Porges, 2007). RSA reactivity is measured as RSA withdrawal (i.e., decreased RSA) or activation (i.e., increased RSA) and what is normative is a function of expected direction and magnitude of change under specific conditions. In general, atypical RSA reactivity has been found to be related to problem behaviors and family risk factors, with most research focusing on RSA withdrawal in challenge contexts. RSA withdrawal in challenge contexts is normative and lack of withdrawal or significantly greater than average withdrawal may be considered atypical. For example, infants who failed to show expected RSA withdrawal to mothers’ still-face were less positive and more physiologically aroused during normal play interactions prior to the still-face (Moore & Calkins, 2004). Greater than average RSA withdrawal during a stressor, suggesting a physiological hyper-reactivity, was found to be associated with more anger in three- to five-year-olds (Donzella, Gunnar, Krueger, & Alwin, 2000). In mothers, those rated lower in sensitivity showed a lack of RSA withdrawal during the reunion episode of the SFP, a context in which RSA withdrawal was normative due to the challenge of supporting the resumption of social interaction with infants (Moore, Hill, Propper, Calkins, Mills-Koonce, & Cox, 2009). To date, little is known about infants’ or mothers’ RSA reactivity to anger, although there is evidence that infants react behaviorally to anger and evidence that qualities of parenting that are likely to be undermined by anger between adults are associated with infants’ physiological regulation.