CNN.com - The screen-age: Our brains in our laptops - Aug 2, 2004: "McLuhan believed our senses become extended outside of our bodies. He suggested that a book was an extension of your eye and a car, an extension of your foot. He would say the Internet is an extension of our central nervous systems.
If we think of ourselves as somehow projected outside our bodies, one's sense of self becomes increasingly fragmented. My math brain lives partly inside a calculator.
My consciousness isn't just split between gray matter and a hard drive or two. Now part of it lives on the Internet and seems to stay there all the time. While I may feel a bit diffuse, mostly I observe changes in what McLuhan called our 'sense ratios,' like a goldfish changing from one kind of aquarium to another. We adapt. We gain some things, lose others."