A good friend recently had his first child, a son, allowing my friend to join the growing number of my peers who now call themselves parents. I’m always astounded at how sudden and profound the transition is from pre-baby to parent. One day you go to sleep expecting to wake three snoozes into your alarm, and 20 hours of labor later, you go to sleep expecting to wake up whenever this tiny new creature beckons. Then, you have to be ready to feed, soothe, or rock the little guy back to quiet slumber. With so many things to learn—immediately—to care for a baby, it seems like evolution must have given our brains a few tools to ease the shift into the newfound role as parent, just as a bird shifts to its nesting instinct. That’s why, when I saw a recent study looking at how oxytocin affects our brain’s response to babies, I grew curious.
Dutch researchers Madelon Riem and Marinus van IJzendoorn at Leiden University, two of the study’s authors, found that oxytocin changes the way the brain responds to a baby’s laughter. Specifically, oxytocin enhanced connections between brain regions involved in reward and emotion when listening to the laughter of an infant. This brain response may be important for blossoming affection toward the child, and may also drive the parent’s care-taking. Motivating such parent-child bonding promotes better parenting and ensures the child’s safety to grow and thrive.
Although anyone might enjoy listening to an infant’s glee, as Riem and van IJzendoorn suggest, “The laugh of an infant is a uniquely rewarding experience for parents.” It ought to be. Something has to make up for diapers and sleep deprivation.
How did they test it?
Riem and van IJzendoorn tested the brains of 42 women who had never been pregnant using MRI scans as they listened to sounds of a baby laughing, crying, or listened to similar sounds that could not be identified as laughter or crying. Twenty-two of the women were given a dose of oxytocin immediately before the scan and the rest were given a placebo. Oxytocin, often called the “love hormone” because it promotes trust and affection, is higher in parents who have stronger bonds with their children.
Oxytocin also promotes both mothering behavior and playfulness in fathers, although it’s not clear exactly how it does this. Riem and van IJzendoorn tested whether oxytocin might change the way we perceive an infant’s laughter, one of the earliest vocalizations a child makes. By giving subjects a dose of oxytocin, the authors aimed to understand how someone’s reaction to one’s own child, or one they cared about, might differ from their reaction to a stranger’s child.
What did they find?
Compared to placebo, oxytocin changes the way the brain responds to a baby’s laughter. When hearing a baby’s laughter, oxytocin led to reduced activation in the amygdala, a brain region involved in processing fear, threats, and anxiety. Oxytocin also enhanced the connections between the amygdala and other regions of the brain, such as the orbitofrontal cortex, the region just above your eyes, and the anterior cingulate, a frontal region right in the groove between the two hemispheres of the brain. The orbitofrontal cortex, or OFC, and the anterior cingulate cortex, or ACC, help process emotions and relay that information to other parts of the brain.
Riem and van IJzendoorn suggested that the changes resulting from oxytocin are likely important in fostering parenting behavior. They write, “Increased functional connectivity between the OFC, ACC, and amygdala may promote mother-infant attachment by enhancing cognitive control over negative emotionality.” Anxiety and other negative emotions might distract the mother from parenting, so by decreasing these feelings she can focus her energy on meeting the child’s needs—like bonding.
Although Riem and van IJzendoorn did not test males, oxytocin likely has similar effects on a father’s brain. A past study found that fathers with higher oxytocin levels played more and had more stimulating interactions with their child.
What does it mean?
This study offers a brain-based explanation of the value of an infant’s laughter and helps explain the father’s behavior in the YouTube video linked below, where he keeps making silly sounds to prolong his child’s mirth (it may also explain why laughing baby videos get so many hits!). As Riem writes, “infant’s laughter may activate neural reward centers in the parental brain and reinforce parental playful interactions.”
Why is a baby’s laughter so intoxicating? So you’ll want to make him laugh again.
Source: Riem MM, van Ijzendoorn MH, Tops M, Boksem MA, Rombouts SA, Bakermans-Kranenburg MJ. No Laughing Matter: Intranasal Oxytocin Administration Changes Functional Brain Connectivity during Exposure to Infant Laughter. Neuropsychopharmacology. 2012 Apr;37(5):1257-66.
Thanks to Karen Kaplan for insights and suggestions.
Joshua Gowin, Ph.D., earned his doctorate in behavioral neuroscience at the University of Texas Health Science Center in Houston.