Brief Report Parenting Behaviors and Vagal Tone at Six Months Predict Attachment Disorganization at Twelve Months ABSTRACT: The authors investigated the relationships among parenting behaviors, infant vagal tone, and subsequent attachment classification. Vagal tone was assessed among 6-month olds (n ¼ 95) during the still-face paradigm (SFP) via respiratory sinus arrhythmia (RSA), while attachment security and disorganization were measured at 12 months during the strange situation procedure (SSP). Infants demonstrating higher levels of RSA during the normal interaction and reunion episodes of the SFP whose mothers were also rated as negative-intrusive exhibited higher levels of attachment disorganization at 12 months, while infants with lower RSA and mothers who were negative- intrusive did not exhibit higher levels of disorganization. These results suggest that high levels of RSA may not be adaptive within the context of negative- intrusive parenting. ß 2014 Wiley Periodicals, Inc. Dev Psychobiol Keywords: attachment; parenting; vagal tone; RSA; biological sensitivity to context INTRODUCTION High levels of vagal tone are thought to promote a state of calm engagement that is conducive to social communication and interaction (Porges, 2007), and thus high levels of vagal tone may be particularly adaptive for young children, who depend on interactive exchange with caregivers to scaffold their nascent self- regulatory abilities (Calkins & Marcovitch, 2010). However, results recently reported by Conradt, Meas- elle, and Ablow (2013) cast doubt on this “main effects” perspective, indicating instead that the associa- tion between high vagal tone and developmental out- comes may be contingent upon environmental context, and specifically, on the quality of the parent–child relationship in early childhood. Whereas Conradt and her colleagues demonstrated that the association of high vagal tone with later problem behaviors was contingent upon the quality of parent–child attachment bonds in late infancy, in the current study we examined whether the relationship between high vagal tone and attachment was moderated by parent behavior in early infancy. The 10th cranial or vagus nerve is one of five cranial nerves that regulate the motor pathways controlling the striated muscles of the face, and thus permit much of social interaction (Porges, 2001, 2003). The vagus nerve also innervates the heart, exerting an inhibitory influence that keeps heart rate low and the variability of the interval between heartbeats high. This variability is commonly referred to as vagal tone, and is often indexed by the amplitude of respiratory sinus arrhyth- mia, or RSA. High levels of vagal tone at rest have been linked to better socioemotional outcomes in adults (Kok & Fredrickson, 2010; Oveis et al., 2009), while both resting levels of vagal tone and reductions in vagal Manuscript Received: 8 July 2013 Manuscript Accepted: 7 April 2014 Correspondence to: Steven J. Holochwost Article first published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/dev.21221  ß 2014 Wiley Periodicals, Inc. Developmental Psychobiology Steven J. Holochwost 1 Jean-Louis Garie ´py 2 Cathi B. Propper 2 W. Roger Mills-Koonce 3 Ginger A. Moore 4 1 Department of Psychology Georgetown University 306N White-Gravenor Hall, 37th and O Streets, N.W., Washington, District of Columbia, 20057 E-mail: sh1158@georgetown.edu 2 Center for Developmental Science University of North Carolina at Chapel Hill Chapel Hill, North Carolina 3 Department of Human Development and Family Studies University of North Carolina at Greensboro Greensboro, North Carolina 4 The Pennsylvania State University University Park, Pennsylvania