[acdha]

That’s off by about an order of magnitude – highly skilled humans can see and react in less than 120ms. One thing which can complicate discussion on this is that there are different closely related things: how quickly you can see, understand, and react is slower than just seeing which is slower than seeing a change in an ongoing trend (that’s why you notice stutter more than isolated motion), and there are differences based on the type of change (we see motion, contrast, orientation, and color at different latencies due to how signals are processed starting in the cortex and progressing through V1, V2, V3, V4, etc.) how focused you are on the action (e.g. watching to see a bird move is different than seeing the effect of something you’re directly controlling). Audio is generally lower latency than visual, too.

All of this means that the old figures are not useful as a rule of thumb unless your task is exactly what they studied. This paper notes how unhelpful that is with ranges from 2-100ms! They found thresholds around 25ms for some tasks but as low as 6ms for some tasks.

https://www.tactuallabs.com/papers/howMuchFasterIsFastEnough...

Keyboard latency is one of the harder ends of this spectrum: the users are focused, expecting a strong (high contrast, new signal) change in direct response to their action, and everything is highly trained to the point of being reflex.

When I’m typing text, I’m not waiting for the change to hit a key outside of games but rather expecting things like text to appear as expected or a cursor to move. Awhile back I tested this and the latency difference between VSC’s ~15ms key-to-character was noticeably smoother compared to 80+ms (Atom, Sublime) and the Citrix system I tested at 120-150ms (Notepad is like 15ms normally) was enough slower that it forced a different way of thinking about it (for me, that was “like a BBS” because I grew up in the 80s).

n.b. I’m not an expert in this but worked in a neuroscience lab for years supporting researchers who studied the visual system (including this specific issue) so I’m very confident that the overall message is “it’s complicated” even if I’m misremembering some of the details.