Infant and Maternal Sensitivity to Interpersonal Timing Anne Henning Saarland University Tricia Striano Hunter College A perturbation paradigm was employed to assess 3- and 6-month-old infants’ and their mothers’ sensitivity to a 3-s temporal delay implemented in an ongoing televised interaction. At both ages, the temporal delay affected infant but not maternal behavior and only when implementing the temporal delay in maternal (Experiment 1, N = 64) but not infant (Experiment 2, N = 60) behavior. In addition, the experimental manipu- lation influenced promptness of maternal smiling responses reliably more than promptness of infant smiling responses. The findings suggest that the timing of maternal behavior plays an important role in infants’ per- ception of maternal responsiveness, whereas mothers seem to monitor general aspects of infant behavior such as overall level of engagement. All behavior unfolds in time. The temporal coordi- nation of behavior, that is, changes in the timing of one individual’s behavior in relation to the timing of another’s behavior, has been called the ‘‘bedrock of all social interaction’’ (Crown, Feldstein, Jasnow, Beebe, & Jaffe, 2002). By temporally coordinating their behavior, individuals confer a predictable structure to the interaction. More important, the perception of their temporal coordination may enable them to experience a sense of togetherness (see Hobson, 2002). From early on, infants perceive a variety of temporal information such as duration, rate, and rhythm and, like adults, detect temporal variations in the millisecond range (Fraisse, 1963; Lewkowicz, 2000). Already by 2 months of age, infants temporally coordinate their behavior with that of an adult in dyadic interaction (e.g., Crown et al., 2002; Jaffe, Beebe, Feldstein, Crown, & Jasnow, 2001; Kaye & Wells, 1980). This suggests that the temporal worlds of caregiver and infant may meet long before their cognitive worlds do. Research on early face-to-face interaction has focused on the quality or content of parental behav- ior as well as its contingent relatedness and tempo- ral coordination with infant behavior to explain which aspects of parental behavior may enable the infant to feel that her subjective experience is shared by the parent (see Harrist & Waugh, 2002, for a review). Parents often imitate infant vocal and non- verbal behavior (e.g., Papous ˇek & Papous ˇek, 1989) and mirror the infant’s level of arousal and affective experience by matching the categorical quality and the vitality contour of the infant’s expression (e.g., Gergely & Watson, 1999; Stern, 1985). By providing a turn-taking structure and contingent responses to infant signals (e.g., Kozak-Mayer & Tronick, 1985), parents enable the infant to experience reciprocity and a sense of agency (Nadel, Prepin, & Okanda, 2005). The perception of this social contingency is likely facilitated by the promptness of parental responses (van Egeren, Barratt, & Roach, 2001; Kel- ler, Lohaus, Vo ¨ lker, Cappenberg, & Chasiotis, 1999; Papous ˇek & Papous ˇek, 1987). Importantly, parental response latencies of 1–2 s fall within the 3-s time interval that infants require to detect a contingent relation between their own action and a following effect (Millar & Watson, 1979; Watson, 1967). The timing of parental behavior may thus play a crucial role for the infant’s developing sense of agency as well as for experiencing early intersubjectivity. It provides infants with a cue for detecting the contin- gent relatedness of their parents’ behavior. Hence, it enables infants to experience themselves as causally affecting parental behavior and to experience paren- tal behavior as a meaningful response to their own behavior (van Egeren et al., 2001). Thank you to Kerstin Tra ¨ger, Caterina Bo ¨ ttcher, and Felicitas Rost for help with data collection and coding, and to Roger Mun- dry and Daniel Stahl for statistical advice. We are grateful to Alex Burkhardt for help with the figures and technical support, and to Petra Jahn for help with setup and technical support. We are also thankful to the staff of the Universita ¨tsfrauenklinik in Leipzig for their support with infant recruitment and especially to the parents and infants who participated in the study. Correspondence concerning this article should be addressed to Anne Henning, Developmental Psychology Unit, Saarland Uni- versity, PO Box 15 11 50, Saarbru ¨ cken 66041, Germany. Elec- tronic mail may be sent to a_henning@mx.uni-saarland.de. Child Development, May ⁄ June 2011, Volume 82, Number 3, Pages 916–931 Ó 2011 The Authors Child Development Ó 2011 Society for Research in Child Development, Inc. All rights reserved. 0009-3920/2011/8203-0015 DOI: 10.1111/j.1467-8624.2010.01574.x