1 Department of Psychology, Centre for Research in Human Development, Concordia University, Montreal, Quebec, Canada.
2 Department of Psychology, University of Utah, Salt Lake City, Utah, USA.

Touch is a central component of mothers' and infants' everyday interactions and the formation of a healthy mother-infant relationship. Twelve mothers and their full-term infants from the Midwest, USA participated in the present study, which examined the quality and quantity of their touching behaviors longitudinally at 1-, 3-, 5-, 7-, and 9-months postpartum and within two normative interaction contexts (face-to-face, floor play). Findings revealed that mothers' and infants' individual touch patterns, varied according to context, infant age (time), and the specific type of touch examined. At 1-month postpartum, dyads coordinated their touch via behavioral matching and were especially reliant on rudimentary types of touch with soothing and regulatory properties (static/motionless touch, stroking). As infants aged to 9-months, dyads transitioned to a more complex form of tactile synchrony characterized by the parallel use of complementary types of touch (grasp, poke, pull). This evolution of tactile synchrony may reflect infants' growing behavioral repertoire and increased capacity to use more refined forms of touch. To our knowledge, this study was the first of its kind, uniquely contributing to the scant knowledge about the development of mother-infant touch and synchrony and offering direct implications for early care practices and infant health and well-being.