problem with short ISI

[Michiel Spape]

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




This message has been checked for viruses but the contents of an attachment
may still contain software viruses, which could damage your computer system:
you are advised to perform your own checks. Email communications with the
University of Nottingham may be monitored as permitted by UK legislation.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en
-~----------~----~----~----~------~----~------~--~---