4 ms·

Imagine you have a system that ignores taps a substantial percentage of the time (either because it required more precise finger placement, or because that's li

Imagine you have a system that ignores taps a substantial percentage of the time (either because it required more precise finger placement, or because that's life). Also most successful taps complete quickly, with only some having 250ms latency. Combine these two and most of time when nothing has happened after 250ms, it's because the tap failed to register and a new tap attempt is needed. There's been plenty of research for decades showing that 250ms response time in UX is a noticeable slowdown.

maicro 2y ago
I had a similar comment so I'll just add-on here - jitter definitely is a huge issue. If an interface is _consistently_ slow you know to slow down, space out actions and wait for visual confirmations; if an interface is generally responsive, though, you can get into a "rhythm" of actions which, which can lead to chaos and confusion as you try to figure out both the new state of the system, and what actions you need to take to get back on track.
- QuercusMax 2y ago
  This is exactly what triggered the Therac-25 radiation therapy defect: the UI was very slow to update, but experienced users knew what order to hit the buttons to go through the screens quickly. Except that there was a bug where if you go too quickly, some of the software safety interlocks didn't work right, and they had removed the hardware safeties in the update from Therac-20.
NoMoreNicksLeft 2y ago
What's the latest research show for a reasonable latency for something like this, anyone know?
- shepherdjerred 2y ago
  https://www.semanticscholar.org/paper/How-Much-Faster-is-Fast-Enough%3A-User-Perception-of-Deber-Jota/cd4c54600245f906667d469b02ed551350ee64ff https://www.semanticscholar.org/paper/How-Much-Faster-is-Fas...
  - NoMoreNicksLeft 2y ago
    Wow. I can believe it needs to be sub-250ms, but some of that is a little ridiculous. 60ms? Maybe I'm just old and my fast-twitch game's weak...

maicro 2y ago

I had a similar comment so I'll just add-on here - jitter definitely is a huge issue. If an interface is _consistently_ slow you know to slow down, space out actions and wait for visual confirmations; if an interface is generally responsive, though, you can get into a "rhythm" of actions which, which can lead to chaos and confusion as you try to figure out both the new state of the system, and what actions you need to take to get back on track.

QuercusMax 2y ago
This is exactly what triggered the Therac-25 radiation therapy defect: the UI was very slow to update, but experienced users knew what order to hit the buttons to go through the screens quickly. Except that there was a bug where if you go too quickly, some of the software safety interlocks didn't work right, and they had removed the hardware safeties in the update from Therac-20.

NoMoreNicksLeft 2y ago

What's the latest research show for a reasonable latency for something like this, anyone know?

shepherdjerred 2y ago
https://www.semanticscholar.org/paper/How-Much-Faster-is-Fast-Enough%3A-User-Perception-of-Deber-Jota/cd4c54600245f906667d469b02ed551350ee64ff https://www.semanticscholar.org/paper/How-Much-Faster-is-Fas...
- NoMoreNicksLeft 2y ago
  Wow. I can believe it needs to be sub-250ms, but some of that is a little ridiculous. 60ms? Maybe I'm just old and my fast-twitch game's weak...