Gargling (same root as 'gurgle') is the human act in which air from the lungs is bubbled through a liquid in the mouth. It usually requires that the head be tilted back, allowing a mouthful of liquid to sit in the upper throat. The head can be tilted by tilting either the neck or the back, depending on what is comfortable for the gargler. Vibration caused by the muscles in the throat and back of the mouth cause the liquid to bubble and percolate through the throat and mouth cavity. A study in Japan has shown that gargling water a few times a day will lower the chance of upper respiratory infections such as colds, though some medical authorities are skeptical.