Sex differences during humor appreciation in child-sibling pairs

Abstract

The developmental origin of sex differences in adult brain function is poorly understood. Elucidating neural mechanisms underlying comparable cognitive functionality in both children and adults is required to address this gap. Humor appreciation represents a particularly relevant target for such developmental research because explanatory theories apply across the life span, and underlying neurocircuitry shows sex differences in adults. As a positive mood state, humor is also of interest due to sex differences in rates of depression, a disorder afflicting twice as many women as men. In this study, we employed functional magnetic resonance imaging (fMRI) to investigate brain responses to funny versus positive (and neutral) video clips in 22 children, ages 6–13 years, including eight sibling-pairs. Our data revealed increased activity to funny clips in bilateral temporo-occipital cortex, midbrain, and amygdala in girls. Conversely, we found heightened activation to positive clips in bilateral inferior parietal lobule, fusiform gyrus, inferior frontal gyrus, amygdala, and ventromedial prefrontal cortex in boys. Many of these effects persisted when looking at sibling-pairs only. We interpret such findings as reflecting the presence of early sex divergence in reward saliency or expectation and stimulus relevance attribution. These findings are discussed in the context of evolutionary and developmental theories of humor function.

Keywords:

• Humor appreciation
• Sex differences
• Reward
• Children
• fMRI

Acknowledgments

This study was supported by grants from the Lucile Packard Foundation for Children's Health (LPFCH), Spectrum Child Health, Clinical, and Translational Science Award to ALR and JMB, and the Bette and Al Moorman Young Investigator Award to ALR. Funding for PV was provided by a fellowship for advanced researchers from the Swiss National Science Foundation (grant N° 136480). Funding for JMB was provided by an NIH-sponsored institutional research training grant (T32) 5T32MH019908-17 to ALR. Funding for MNN was provided through a major grant from the Vice Provost for Undergraduate Education (VPUE) at Stanford University. We thank John Lyman, Emilie Qiao and Jennifer Gonzales for support in behavioral data collection.