system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it impossible to swallow rapidly over and over with nothing in your mouth, but chugging water is easy?
gpt
Swallowing solids and liquids works slightly differently.

Swallow with an empty mouth and pay attention to what you're doing: The tip of your tongue presses against the roof of your mouth just behind your teeth, then 'rolls' along the roof of your mouth backwards towards your throat.

Basically, it's two actions: You open your throat and your tongue forces your food towards it.

When you chug water, you don't do that. There's no need to force the liquid to the back of your mouth, because your head's tipped back and gravity takes care of that for you...basically all you're doing it rhythmically opening and closing your throat.

So, swallowing with an empty mouth is a complex action, and because you're not swallowing anything but saliva and air, you have to manually 'reset' your tongue between swallows.