Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!ami!royc From: royc@ami.UUCP (roy crabtree) Newsgroups: comp.protocols.tcp-ip Subject: Re: human factors aspects of echo delay Summary: refresh and echo rates need to be faster still to minimize parallel event tracking errors Message-ID: <169@ami.UUCP> Date: 6 May 89 18:57:49 GMT References: <8904261932.AA00175@gateway.mitre.org> <01-May-89.183043@192.41.214.2> Organization: Access Methods, inc. Lines: 81 In article <01-May-89.183043@192.41.214.2>, amanda@lts.UUCP (Amanda Walker) writes: [elided] > time" of conscious processing is about 1/20th of a second, i.e. events > occurring at 50ms intervals are greater can be perceived as separate > events, whereas events occurring at shorter intervals are perceived > as simultaneous, depending somewhat on what kinds of events are being ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > correlated. For example, a video terminal running at 300 baud in > full duplex gives most people the illusion that the letters are appearing > as they type (66ms). However, motor skills (such as tracking moving The event sync rate on output must be about 2* the event input rate if more than one event is to be tracked, or if parallel events are being tracked; otherwise, a single serial event on output will perceive under _low_stress_ conditions as 'simultaneous' if it within around 1-1.5 input event intervals after the _end_ of the input event correlated with it. Several military studies correlate this; sorry, no refs. > objects) involve much more fine-grained timing (hmm... hardware buffers :-)?) Yep, may be needed for speed. Again, the reason is that the event being perceived is correlated, not against the keyboard input event, but against the eye/screen coordinative cognition that _follows_ it; since the granularity of the eye is spatially higher, it tends to be temporally higher as well (udderwise ya caint do nuthin wid it anyways so why bother seing it?) > For example, animation at 60 or 120 frames/sec will look much smoother and > more "realistic" than at 30 frames/sec, even if there's no consciously > perceptible flicker... Hurray, Disney! (Frame rate minimums of 31-36 FPS preferred) > > Part of the point of this is that how fast the feedback needs to be depends > a lot on what you're feeding back. Keystrokes can probably get by with > 50-80ms. Rubber-band lines need to be 15-30ms, and so on. This is true. However, the rates are still too slow, I would think. The rationale I have is as follows: - You can perceive whart you can do. - A musician can play (i.e., do) music at tempos of up to 240-300 beats per minute: 5 times per second. - The beat may be subdivided 2-4 times (or more!) at those rates for individual notes: 20 times per second (from which comes the 50 millisecond figure) - Positive correlative events (things you have to perceive against prior to actions subsequent and dependent on them for correct function or response) usually should have no more that a 5-10% transit delay against the response interval, to avoid upsetting the goal oriented resonse of the operator involved. This should also apply in terms of a spatial perception sense: The position of hte item being viewed or tracked or clicked or stretched should be no more 5-10% of the _immediate_significant_visual_field_ off in terms of timing. So, for character IO, since you do not correlate but every so often (you don't read every character!) 50 msec is probably OK (but better 25!) But for rubber band lines, 10-25 msec under rapid mouse drag motions. And for supercritical events, such as a popdown or "gotcha!" notification for mouse clicks or state transition, probably 3-8 msec is what is needed for "smooth" perception. If anybody doubts this, try using any old mouse driven terminal with a polled mouse at 60 Hertz clock rate; it is easily possible to click and release the mouse in 1/60th of a second: if you can, then 1/120 of a second is the basic event rate, and 1/2 that (4 msec) is the minimum to achieve _perceptibly_continuous_motion_. > > -- > Amanda Walker > InterCon Systems Corporation > amanda@lts.UUCP / lts!amanda@uunet.uu.net roy a. crabtree uunet!ami!royc 201-566-8584