It is actually very interesting. Once you have a baby, you get to understand many things. The reason why is, because when they are in the belly, this is what they hear. SHHHHHHHHHHHHHH... So this white noise, brings them back to the womb. Fun fact : This is also the reason why a slow heartbeat relaxes you, whereas a high heart rate makes you stressed. Additionally.. This is why you shush babies. When you want them to be quiet.. You tell em shhh... This os where it comes from. Also kissing is no different from drinking milk. When you kiss someone you essentially go back to that point of your life. Anf why do you shake your head left amd right to give "no" for an answer? Because, when you were a baby, this is how you said no. By declining food. They pull their head back and avoid the spoon left and right.