Hair cells are inaccessible and fragile, so the most obvious superear idea—of improving hearing with more or better hair cells—is unpromising. In theory, you might use gene therapy to grow extra hair cells. (A hair cell could be engineered to detect high, dog-friendly frequencies, for example.) But the prospects for this seem remote for several reasons. First, scientists can't figure out how to make hair cells grow after infancy—they seem uniquely resistant to revival. Second, the distant, protected inner ear would be an incredibly hard place to try gene therapy. (Most promising gene therapy so far has been limited to small genes in accessible places.) And third, and most important, even if you could get the ear to grow lots of new hair cells, it's not clear you'd hear better. According to the House Ear Institute's Andy Groves, a researcher on hair cell regeneration, it's possible that having more hair cells may impair hearing rather than improve it. The mammalian inner ear has evolved to be highly mechanically sensitive. Adding extra hair cells may well disrupt the mechanical response of the ear to sound vibrations.