Clicking the play button below will produce a tone that is generally only heard by people under the age of 25. It has been used as a deterrent device to keep teenagers from loitering in malls and shops, and sounds similar to a buzzing mosquito. Typically the longer you listen to it, the more annoying it gets.

In a highly literate society, almost everyone becomes myopic because their eyes elongate beyond the threshold for myopia. Thus the impact of genes disappears, although it might still be seen in eye length and the severity of myopia.