Why do humans come to sleep when they realize they are on the train? Humans have incorporated the origin of life into their genes since ancient times. Life was once born in the sea. The kanji is sea = water + every. Plum = tree + every, and it is helpful that plums have grown and connected their lives with fruits that are descendants every year. The baby grows up in the mother's stomach, wrapped in sea-like amniotic fluid. At that time, the fetal hearing is already functioning and it seems that it is already listening to the sounds of the outside world.

For example, when you're swimming in a pool, you can hear the surrounding sounds near the surface of the water. This is similar to a foetation in amniotic fluid, and you probably hear the mother's regular heartbeat and blood flow in the amniotic fluid. This old memory has been left in deep psychology for a long time. Therefore, when I hear the sound of the waves crashing on the beach at night, I feel nostalgic for some reason.

In fact, even as an adult, when you get on the train, the sound environment revives the memory you gained during the fetal period. It is thought that remembering the sense of security and comfort makes you feel comfortable and leads to drowsiness. As a reference event, it has been demonstrated that listening to the sound of the mother's heart in a sick child stops crying. It is already being used in childcare settings.

Doctor of Medicine Hiroshi Bando