"I'm counting on the technology to develop and extend my mind faster than my biological mind," says David Walliams. Studies show taxi drivers use their internal mapping systems more intensely than rest of us, so that they're actually growing that part of their brain. We've also read about blind people who use part of the visual cortex for other purposes - such as enhancing their ability to hear and smell. Without these glasses, we would truly become helpless: a scene from Charles Stross' novel accelerato sees main character reduced to gibbering rack.