> When anything takes more than 50ms to react, it becomes mentally jarring to the user. Depends. Pressing a key and not seeing a character in less than 50-100

> When anything takes more than 50ms to react, it becomes mentally jarring to the user. Depends. Pressing a key and not seeing a character in less than 50-100ms, yeah, it's quite frustrating. Clicking on a link and waiting for the content to load? Not so much.