Soothing a baby is any mother or caregivers’ ultimate goal when their infant is crying. Babies’ universal indication of any concern, distress, pain, hunger, or desire is communicated by crying; parents endlessly attempt comforting techniques to relieve their helpless infant. A common response is for a mother to immediately pick the crying baby up and rock or walk with them gently in her arms (Gammie, 2013). Often times, the helpless infant nearly instantly stops or reduces their cries; however, as soon as their mother again puts the baby down, often the cries once again ensue. This recurring pattern exemplifies the elicited automatic calming response that infants exhibit in response to being carried. This comforting mechanism is not selective to human parents exclusively, this dynamic interaction is a comforting method utilized by parents of various mammalian species.
Various other mammals, such as felines and rodents demonstrates what is called the “transport response” in which the crying young assumes an immobile posture while their mother transports them (Esposito et al., 2013). Often the response is relieved stress exhibited by reduced vocal cries. This dynamic “transport response” is also seen in species of mouth-carrying primates (galagos); how is this transport response translated to humans and what is happening in the brain to activate this soothing response?
One study at the RIKEN Brain Science Institute in Saitama, Japan explored the infant physiological responses to their mothers, aiming to further examine this effective coddling parent technique. More specifically, the response of infants under the age of 6 months was examined as their mothers’ exhibited different behaviors. This study examined the behavior, vocalization, and electrocardiogram of infants during three experimental conditions: lying in a crib, being held by their mother in a stationary crib, and being carried by their mother as she walked continuously. In comparison to being in their crib, both being held by a stationary mother, as well as being carried by a walking mother exhibited decreased voluntary movement, vocalization, as well as a rapidly declining heart rate; a similar pattern of results was shown between infants being held by a stationary mother and infants being carried by a walking mother. These results showed that physical contact from the mother elicits comfort in the infant; mobile transport combined with physical contact elicits even greater comfort.
What is happening neurologically to produce such calming responses, as exhibited both physiologically and behaviorally? Exhibited by infants in this study, heart rate analysis identified differences in parasympathetic activity based on interbeat measurements; increased duration of interbeat index measurements within the infants being carried by a walking mother indicated that infants were more relaxed. Previous research suggests that maternal physical touch combined with rocking motion provides vestibular-proprioceptive stimulation; these results suggest that walking movement has a similar stimulating mechanism, resulting in heightened calming effects on infants. Furthermore, maternal walking provides infants with calming sensory inputs in a synergic manner, eliciting possibly the most effective calming response (Esposito et al., 2013).
Esposito, G., Yoshida, S., Ohnishi, R., Tsuneoka, Y., del Carmen Rostagno, M., Yokota, S., … & Kuroda, K. O. (2013). Infant calming responses during maternal carrying in humans and mice. Current Biology, 23, 739-745.
Gammie, S. C. (2013). Mother–Infant Communication: Carrying Understanding to a New Level. Current Biology, 23, R341-R343.