UI / reaction time - was: Re: 23 branch - can't push - lock

[David Reitter <david.reitter@gmail.com>]

On Jun 17, 2011, at 11:39 AM, Eli Zaretskii wrote:
> How do you mean "discernible"?  Most humans are generally unable to
> react in less than 200-300ms, so 30ms is an order of magnitude off the
> mark.

Reaction requires a chain of not only perception and related encoding, but also planning possibly moderated by execute control, possibly memory access, motor planning and actual execution.  That takes time.  In some cases, after some reactions have been routinized, you can sidestep much of that, and react more quickly.  That said, not reactions are relevant, but change detection and perceived duration.   Current cognitive modeling frameworks assume a 50ms "clock" for cognitive processing (simple, IF-THEN rules, for instance, in Anderson's ACT-R), and this is where I derived this figure.  You may be right in that more than that  is needed to estimate relative duration, let alone be bothered by a wait.   Some people can perceive duration in a visual stimulus in around 100ms (a study by Efron in 1970 found 120ms as minimum).  Change detection seems to be similarly quick when subjects attend to the location (Pashler 1988).

We may both be missing the point with this, though.  At around 1s, isn't it much more about what users "feel" is fast or a delay, as opposed to whether they can make use of the actual speed-up?

The figures you obtained (less than 1 sec) seem OK to me (subjectively), while the pauses I experienced (several seconds) seemed unpleasant.  They were at a larger scale than that.

Thanks for the hints regarding speeding up bzr and undoing a commit.  I'll leave that portion of the discussion, as it has little to do with Emacs, as Stefan pointed out.