having the computer create variable interstimulus intervals

[I][edited by moderator][/I]
I am trying to design a task in which I give all subjects the same total duration, e.g. 60 stimuli in 120 seconds--but to vary the ISI between stimuli across subjects. I do not know how to do that in DirectRT. I would really appreciate if you could get back to me in this matter.
thanks
maya .

You can use a constant interval in the style (.drt) file but add a blank stimulus to the end of each trial in your input file, like this:

stim = ~
loc = 1,1,1
time = 500

That would give you a 500ms ISI for that trial. For a 300ms ISI, you simply change it to:

stim = ~
loc = 1,1,1
time = 300

And so on. You can also have these values be random, or randomly chosen from a set. For that see, [URL="http://www.empirisoft.com/directrt/help/directrt_using_random_values.htm"]www.empirisoft.com/directrt/help/directrt_using_random_values.htm[/URL]