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I feel like it's a subset of a much larger, more general topic of how latency impacts computer interactions. People have long tried to emulate real-world activities in computer programs, but not much attention has been paid to making those programs instantaneous.

When you mold clay, there is no lag - the tactile and visual feedback is immediate. Same with handwriting, painting, or petting a dog. On the other hand, even in this current world of multi-core 4Ghz+ computers most software fails to provide immediate feedback.

100ms, I believe, is the magic number. The maximum delay between cause and effect that still registers as "instantaneous" by the human brain. Yet, surprisingly, it's still a rarely reached target. FPS video game studios might be the only major industry that consistently cares about and delivers on this metric. (Edit: "major" was an intentionally vague word to use here. Obviously, all kinds of embedded software projects have to deal with real-time or soft-real-time requirements.)

If reformatting the whole current code file took 1ms, why wouldn't you enable it? If compilation took 50ms, why not recompile on each new line? There's a magic latency barrier below which actions feel "free", so why not try and move as many of them as possible below that threshold?

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> When you mold clay, there is no lag

Wonderful phrasing.

On the importance of immediate feedback in the creative process, it reminds me of audio/music production - in particular, MIDI instruments. The latency between keypress and sound reaching the ear should be as close to zero as possible.

Recently I read a discussion about remote collaborative music performance. From what I understood, network latency is not nearly low enough to achieve it. There's also the physical limit of the speed of light.

10ms was mentioned as acceptable for musicians - but then someone said, even when musicians are in the same room, there can already be too much latency if it's a big room and they're distant from each other, making it difficult to play together.

> why not recompile on each new line?

This is becoming the standard in web development, with incremental compilation (and "hot reload" on the client) of only the changed code/module. I saw that it's getting applied in building mobile apps as well, to get closer to the ideal of instant feedback.

In thinking of the ideal developer experience, I often come back to Bret Victor's work, Learnable Programming. http://worrydream.com/#!/LearnableProgramming

> 10ms was mentioned as acceptable for musicians - but then someone said, even when musicians are in the same room, there can already be too much latency if it's a big room and they're distant from each other, making it difficult to play together.

Sound only travels ~3.4 meters in 10 ms, so it matches up that a large venue easily exceeds that quite a bit.