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

[David Reitter]

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.