Born to Be Good: The Science of a Meaningful Life

In stunning research, Darlene Francis and Michael Meaney have examined how a pattern of licking and grooming directed by rat mothers, or dams, to their pups alters the development of the HPA axis, which is the body’s stress system. The researchers first identified those rat mothers who provided a high level of licking and grooming to their pups. This was accomplished by observing patterns of licking, grooming, blanket postures where the mother lies over the pups, and various nursing postures. Francis and Meaney assessed this family of tactile behaviors five times a day for six to eight days postpartum. The licking and grooming are relatively infrequent, constituting about 10 percent of the interactions between mother and pup (the most common postpartum observation is no contact or arched-back nursing). There is tremendous variation in how much each mother licks and grooms her pups. The amount of touch provided has profound consequences.

Francis and Meaney have found that mothers who lick and groom a lot alter the HPA axes of their offspring. They produce young rats who are more resilient to stress. As adults, offspring of mothers who lick and groom a lot show reduced levels of ACTH and the stress hormone corticosterone in response to being stressfully restrained. They show reduced startle responses and a greater tendency to explore novel environments and foods. Perhaps most dramatically, they show reduced receptor levels of stress-related neurons in the brain (decreased corticotropin releasing factor receptors in the locus ceruleus; decreased central benzodiazepine receptors in the amygdala). Touch altered these animals’ nervous systems. Early touch in a rat pup’s life leads to a more resilient and calm rat later in life, endowed with a more robust immune system.

Of course, it is next to impossible to do this kind of precise study of touch and the HPA axis in young humans. A recent study, though, indicates that touch reduces our stress-related physiology. Jim Coan and Richie Davidson had participants wait for a painful burst of white noise—a source of stress—while resting in a fMRI scanner and having images of their brain taken. For the control participants, this stressful period of waiting triggered activation in the amygdala. These participants were showing a well-replicated brain reaction to threat. Other participants waited for the burst of white noise while their romantic partner touched their arm. These participants showed no amygdala response to the threat. Touch turned off the threat switch in the brain.

Touch is woven into our daily exchanges. Pats on the back, handshakes, hands resting on shoulders and arms, and playful nudges are barely noticed as we move through the day. Yet these touches alter others’ nervous systems toward patterns of activation more conducive to higher jen ratios. The stroking of touch-sensitive neurons in the skin sends signals to one reward region of the brain—the orbitofrontal cortex, which activates release of oxytocin and endorphins. At the same time, pleasurable touch reduces activation of the HPA axis, the provenance of stress and anxiety. To touch, Michelangelo said, is “to give life.”

TOUCH AND TRUST

 

Like many an American family, when our children were very young we had sleep arrangements that would leave a hunter-gatherer family, or their prim and proper Victorian counterpart, scratching their heads in disbelief. This was in part because we were torn between these two poles of sleep philosophy—the evolutionarily old and near-universal practice of family members sleeping in physical proximity to one another, and the Victorian innovation of making children sleep alone in dark rooms roiling with shadowy images of monsters and demons.

The product of such cultural ambivalence, we naturally arrived at elaborate bedtime rituals to get our two daughters to sleep. When they were quite young, say four and two, our bedtime ritual took an hour and involved the following: two and sometimes three fairy tales; two stories from my childhood, as long as I was younger than twelve and the stories involved some kind of mammal, some slapstick action on my part, and a subtle moral; one song for each daughter; and then patterns of sitting and lying next to each daughter. Of course one has only so many good stories to tell, and the best selection of the world’s fairy tales can only be so enthralling to the jangled parent’s imagination. Like many parents, I often was at wit’s end during this ritual, plagued by visions of walking out the front door and hitchhiking across the country, and resorting, as a way to pass the time, to counting the minutes until their puberty would cast me out of their room.