What is cost of error correction?

Example: You notice typos in every email you send, so you start proofreading each message three times before hitting send. Your error rate drops, but now a two-sentence reply takes ten minutes. You have traded one cost — embarrassment from typos — for another: time, cognitive load, and a growing backlog of unread messages. The correction eliminated the visible problem but introduced an invisible one. A colleague who uses autocomplete and a grammar checker sends the same quality of email in ninety seconds. She did not get better at correcting — she reduced the conditions that produce errors in the first place.

This concept is part of Error Correction in the How to Think curriculum.