"It's not only humans that can learn from watching television. Software developed in the UK has worked out the basics of sign language by absorbing TV shows that are both subtitled and signed..."

From http://www.newscientist.com/article/dn17431-computer-learns-sign-language-by-watching-tv.html and http://www.boingboing.net/2009/07/09/computer-learns-sign.html ...