problem with short ISI

[susie]

David and Mich,

Thanks so much. I had forgotten about the refresh rate (I am on and
LCD monitor) and you're right, my refresh rate (which I'd checked at
the very beginning of running things) was about 70 Hz. I actually
don't have that many pairings so I think I'll just manually create
single sound files with a 10 ms period of silence.

I'll try the pre-release of the first element, but given the
limitations of the refresh rate, I"m guessing that it won't help.

Thanks,
Susie

On Sep 22, 9:53 am, Michiel Spape <Michiel.Sp... at nottingham.ac.uk>
wrote:
> Hi David, Susie,
> On the second point, you might, if you are using a CRT screen, change
> the resolution and refresh rate in your windows monitor options. In the
> past, it happened quite a lot that discrepancies here between E-Prime
> (1) and windows screen options would lead to refresh rates that were
> different from what they were supposed to be. Check your edat file to
> see what your refresh rate was during the experiment. Also, I don't
> think ISIs of 10 ms with LCD screens are possible, if you happen to be
> using that (the fastest refresh rates I've seen in that department were
> around 70 Hz - 14ms), unless you want half of your screen refreshed at
> some point.
> Best
> Mich
>
> Susie,
>
> Thanks for all the wonderful detail, I wish I had a good answer for
> you!  Just a couple thoughts...
>
> First, can you add a PreRelease to the first sound object?  That
> might allow some time for your ISI blank screen to get set up (I
> don't think the PreRelease on the second sound object does anything
> for you).  Do keep the PreRelease on your ISI as long as
> feasible.  (When I use PreRelease I usually go ahead and make it as
> long as the Duration, or even longer, say 10000.  It doesn't seem to
> matter (short of terminating with a response, etc.), which makes
> sense if you think about what PreRelease really does under the covers.)
>
> Second, as you remember from Chapter 3 of the User's Guide, take a
> look at the Onset and Offset Sync of your ISI blank screen.  If you
> sync with the vertical blank then you will have delays due to waiting
> for the screen to refresh, so you may want to turn that off.  OTOH,
> without syncing to vertical blank you may get brief visual artifacts
> as your blank screen goes on or off.  Just an unavoidable limitation
> of our current technology.
>
> -- David McFarlane, Professional Faultfinder
>
> >I have a vowel discrimination task (vowels are 50 ms each) that I've
> >been presenting at several ISIs (as low as 40 ms and as long as 1500
> >ms). All of these ISIs have been correctly logged (subtracting slide
> >onset of the blank screen from the onset of the second vowel).  I have
> >it set up to play a sound object, have a blank screen for the duration
> >of the specified ISI, and then the second sound object. (I have the
> >ISI blank screen set to preload at 100 ms and the sounds are set to
> >'streaming'. Also, I'm running 2.0 Pro on an XP machine). When I
> >changed the duration of the blank screen to 10 ms I got actual
> >durations from 27 to 40 ms. I've tried adding a preload of 50 to the
> >second sound object and have also tried to reduce the preload on the
> >blank screen to 50 ms and these have not helped.
>
> >Thanks in advance!
> >Susie
>
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