I have two stimuli that need to be displayed 250 times in total.
Image 1 = 48 times
Image 2 = 202 times
They must be randomized though.
Anyway to tell the block to do this?
Yes, selection at the <block> level works according to the proportions given. See the examples in the documentation for the /trials attribute for details. One short example here (many more can be found by searching the forum):
/ trials = [1-10 = noreplace(a,a,b,b,b)]
will result in 4 'a' trials and 6 'b' trials in random order.
Another option is to use a <list> element for trial selection in the respective <block>s' /trials attribute. The desired trial-ratio can be specified via the <list>'s /itemprobabilities.
I am having a 100ms gap between the instructions and the beginning of a blank screen.
The instructions end when 0 key is pressed.I need it to be instant.
Looking through my code I do not see what the cause could be. It's just a random gap of ~100ms between marker data.
Does Inquisit put an automatic 50ms gap between stimulus???
Sorry, I'm not following. (a) What's the relation to the trial-ratio question in this thread and (b) how would anyone know what code you are referring to (I don't see any of that posted)? Can you clarify? Otherwise I can't help here.
No. But you may be mistaken about how trial timings work / the interplay between the various components. For that, see the "How to Control Trial Duration and Inter-Trial Intervals" topic in the docs.
Here is the trials and blocks:<trial instructions>/ stimulustimes = [1=instructions]/ validresponse = ("0")/ errormessage = false/ recorddata = false/ responsemessage = ("0", tPort, 50)</trial>
<trial break>/ stimulustimes = [1=blank, bPort; 50=zeroPort]/ trialduration = values.break/ errormessage = false/ recorddata = false</trial>
<trial warnsound>/ stimulustimes = [0=warnsound]/ trialduration = 500/ errormessage = false/ recorddata = false</trial>
<block instructions>/ screencolor = (0, 0, 0)/ trials = [1=instructions]</block><block warning>/ onblockbegin = [values.break=200]/ screencolor = (0, 0, 0)/ trials = [1=break; 2=warnsound; 3=break; 4=warnsound; 5=break; 6=warnsound]</block>
When I run this there is a gap of 100ms between Instructions and the first break in warning block.
And why is that a problem? Also, why are you running the instructions trial in a separate block? Note that there'll be at least a single frame between <block>s for cleanup.
Whoops. Put it in there. But there is still a delay of about ~88ms from beginning of instruction marker to the beginning of the break marker.