Contagious yawning remains one of the most studied and least understood reflexes in human biology. A new finding about yawning in the womb just made the mystery harder to explain.

Thirty-eight pregnant women at 28 to 32 weeks watched videos and images designed to trigger a yawn. Within 90 seconds of the mother yawning, the baby yawned on ultrasound a significant amount of the time. The researchers confirmed it was not coincidence. The finding matters because we assumed contagious yawning was a learned behaviour that developed over time. Fetuses cannot have learned it yet.

Samantha Yammine’s best current explanation: it may be physiological, something happening in the mother’s body that triggers a reflex rather than imitation. The broader question she keeps returning to is why contagious yawning survived across vertebrates and species at all. Anything that sticks through evolution is doing something. We just do not know what.

Topics: contagious yawning, fetal yawning study, yawning learned behaviour, yawning evolution, yawning mirror neurons

GUEST: Dr. Samantha Yammine | http://samanthayammine.com | @‌science.sam

Originally aired on2026-05-13