Michael Patrick Lynch in The Chronicle of Higher Education:
One way the internet distorts our picture of ourselves is by feeding the human tendency to overestimate our knowledge of how the world works. Most of us know what it’s like to think we remember more from high-school physics or history than we actually do. As the cognitive scientists Steven Sloman and Philip Fernbach have detailed recently, such overestimation extends farther than you might think: Ask yourself whether you can really explain how a toilet or a zipper works, and you may find yourself surprisingly stumped. You assume you know how things work when you often don’t know at all.
This sort of ignorance is partly due to the fact that human beings aren’t isolated knowing machines. We live in an economy of knowledge that distributes cognitive and epistemic labor among specialists. That’s a good thing — no one person can know everything, or even very much. But put all the doctors, scientists, mechanics, and plumbers together, and we collectively know quite a bit.
Yet this often means we blur the line between what’s inside our heads and what’s not. Some philosophers have argued that this blurring is actually justified because knowing itself is often an extended process, distributed in space. When I know something because of your expert testimony — say, that my car’s alternator is broken — what I know is partly in your head and partly in mine. If that’s right, then living in a knowledge economy literally increases my knowledge because knowing is not just an individual phenomenon.
Suppose this extended, distributed picture of knowledge is right. Add the personalized internet, with its carefully curated social-media feeds and individualized search results, and you get not one knowledge economy, but many different ones, each bounded by different assumptions of which sources you can trust and what counts as evidence and what doesn’t. The result is not only an explosion of overconfidence in what you individually understand but an active encouragement of epistemic arrogance.
More here.