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 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 using MRI scans as they listened to sounds of a baby , 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 . Oxytocin, often called the “love ” 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 , threats, and . 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 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 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.

Image credit:flyone

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.