There are two explanation commonly given.
The first is that keeping the tongue in that position allows the throat to open so that saliva can travel downward without stimulating the gag reflex or the need to swallow.
The second explanation is that it somehow connects the meridians which travel in a circle up the back, over the head, and down the front-- popularly called the “micro-cosmic orbit” of the du and ren acupuncture channels.
A while back I wrote about Michael Jordan’s amazing tongue. In an interview he said he learned to do tongue lap-rolls from his father who always rolled his tongue when he was chopping wood. I’ve been experimenting with this for a long time. How does movement of the tongue help the movement of wood chopping? I think I have the answer.
The sucking reflex babies are born with is a whole body movement which comes up from the belly and presses the tongue to the roof of the mouth. Not the tip of the tongue! A spot about a centimeter back from the tip of the tongue presses upward into the roof of the mouth. This creates a rolling effect pushing the tip of the tongue downward and out (to surround the nipple).
If you don’t have a baby handy to play with, find a cat and interrupt her while she is licking herself. She’ll probably stop with her tongue just slightly out of her mouth on a downward arc and give you this Jewish grandmother look like, “What? You want something? No, what makes you think I’m busy?”
If you put your own tongue in this position and try to talk it will sound like, “blublah.” I find that practicing with my tongue in this position is very similar to having “baby feet” (see previous post). It is an even better position for getting saliva to flow down the throat without stimulating the gag reflex. It also seems to interrupt my tendency to think in words. Why did it take me 20 years to figure this out?
This is a very relaxed position of the tongue, it is not held with pressure. Any movement of the dantian (the abdominal region of the mind) will be felt as a subtle change in the shape or fullness of the tongue if it is relaxed. If the tip of the tongue is curved upwards this feedback loop will be broken.
Perhaps this experience is what was originally meant by “connecting the du and ren meridians” but if that is the case, the method and purpose really got mangled in the translation, or the transition to modernity.
(please, no “baby talk” in the comments)
Here is a video of an infant sucking: