Friday quote: Friction / by Dan Lockton

"If the point of contact between the product and the people becomes a point of friction, then the Industrial Designer has failed."

Henry Dreyfuss, Designing for People, 1955

Cognitive friction is one thing, and generally a result rather than a deliberate strategy; process friction is something else, and can very much be a deliberate strategy, as well as an accidental consequence of poor or badly thought-out interaction design. This is closer to what Dreyfuss is getting at, I think.