Washington: Researchers have suggested that infants show unique physiological and behavioral responses to pleasant touch, which may help to cement the bonds between child and parent and promote early social and physiological development.
For the study, cognitive neuroscientist Merle Fairhurst of the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, and colleagues had infants sit in their parents' laps while the experimenter stroked the back of the infant's arm with a paintbrush. The experimenter varied the rate of the brushstrokes among three defined velocities (0.3, 3, or 30 cm per second). The experimenters gauged the infants' responses through physiological and behavioral measures.
The results showed that the infants' heart rate slowed in response to the brushstrokes but only when the strokes were of medium velocity; in other words, the touch of the medium-velocity brush helped to decrease their physiological arousal.
The infants also showed more engagement with the paintbrush during the medium-velocity brushstrokes, as measured by how long and how often they looked at the brush while they were being stroked.
Interestingly, infants' slower heart rate during medium-velocity brush strokes was uniquely correlated with the primary caregivers' own self-reported sensitivity to touch. That is, the more sensitive the caregiver was to touch, the more the infant's heart rate slowed in response to medium-velocity touch.
According to the researchers, the findings "support the notion that pleasant touch plays a vital role in human social interactions by demonstrating that the sensitivity to pleasant touch emerges early in human development."