Carr's research led him to a number of studies that have shown the nature of the Internet is rewiring how our brains work; not only that, but it does so quickly. A study in Boston compared brain scans between veteran Internet users and relative novices. A certain area of the brain of the veteran users lit up while reading web sites, while the novices' did not. Both groups were then sent away for five days with the assignment to use the Internet for one hour a day. After the five days were over, the test subjects' brains were scanned again and the novices' brains lit up in the same areas as the veteran users. Even as little as five hours of Internet use rewires your brain.
Is this a good thing or a bad thing? The answer isn't black and white. Another study shows video gamers can identify more things in their field of vision than non-gamers. Internet usage appears to optimize the multi-tasking parts of our brains, allowing us to move more quickly from item to item. It may even boost our working memory. But, as any good software engineer knows, optimization in one area can slow down another. The process of moving things from our working memory to long-term memory is hindered by Internet use. So while we may be getting what we need quicker, we don't retain it, and our ability to think deeply and create unique insights is becoming weaker.
The book is fascinating, but I have a few quibbles with it. For most of the first third of the book, Carr goes into the history of different media: from when we first developed written language, to the telephone and radio, to motion pictures, and, finally, to the Internet. The long digression provides good background to put the Internet into context with what came before it, but my Internet-addled brain had a hard time staying engaged. There is also a long digression toward the end about the history and culture of Google that I failed to find relevant.
The takeway for this book is the Internet is changing how our brains work and we should be aware of that. Taking time to occasionally unplug is good both for our emotional and mental health and will help us retain the ability to think deeply about problems and find creative solutions.