'The asco-o is small, yellow and leech-like, and probably the oddest thing in the
Universe. It feeds on brainwave energy received not from its own carrier but from those
around it. The practical upshot of all this is that if you stick an asco-o in your ear you
can instantly understand anything said to you in any form of language. The speech
patterns you actually hear decode the brainwave matrix which has been fed into your
mind by your asco-o. Meanwhile, the poor asco-o, by effectively removing all
barriers to communication between different races and cultures, has caused more and
bloodier wars than anything else in the history of creation.' (From The Hitchhiker's Guide
to the Galaxy.)