Why babies laugh, with Gina Mireault, PhD

In this episode of Speaking of Psychology, host Kim Mills interviews Dr. Gina Mireault, a professor of psychology at Vermont State University and director of the Infant Laughter Lab, about the science behind infant laughter. The conversation explores when babies begin to smile and laugh—voluntary smiling around six weeks and laughter typically emerging at four months—and what triggers these responses, such as unexpected sounds, tickling, and incongruous events. Dr. Mireault shares groundbreaking research showing that six-month-olds can detect and laugh at absurd events independently, even when parents remain expressionless, revealing early cognitive sophistication. The episode also examines the social function of laughter as a bonding signal, the development of intentional humor, and the surprising finding that babies with a higher threshold for laughter may form stronger attachments. Cultural influences on humor are discussed, along with cross-species laughter in mammals like rats and dogs, underscoring shared evolutionary roots of joy. Dr. Mireault reflects on her personal journey into this research, sparked by her infant’s reaction to a sneeze, and the challenges of securing funding for 'non-frivolous' science that actually probes deep cognitive development. The episode concludes with insights into ongoing studies on intentionality and incongruity detection in babies. Key takeaways include: 1) Babies laugh at four months as a sign of cognitive development and social understanding; 2) Laughter is a social signal that strengthens caregiver bonds; 3) Infants can detect incongruity and find humor without adult cues; 4) A higher threshold for laughter may correlate with stronger attachment; 5) Laughter has deep evolutionary roots across mammals; 6) Humor is shaped by culture and family context; 7) Intentional humor emerges around six months; 8) Research on infant laughter reveals early cognitive skills like detecting unexpected events. The tone is enthusiastic, insightful, and celebratory of science’s surprises.