Two RSVP streams and dots array with different time durations
Anna Nack
I am trying to make visual stimuli presentation. Have two rsvp images appear every 150 msec with interstimulus interval of 50 msec. WHILE another image (dots arrays) appear 250 msec with interstimulus interval range between 600 and 1400 msec. I have not been able to figure out how to have the two loops proceed independently at the same time. Currently, the only way I have been able to do it is to have the rapidly presenting RSVP stream “stuck” waiting for the slower dot array to finish its presentation.
If someone can help me with figuring out how to have two independent loops, that, that would be great!
Michiel Spape
Hi,
Well, basically, you don’t. It’s perhaps fairly simple in terms of an event-handler based programming language in which you put two timers in place and then hang events to these, but E-Prime doesn’t really work like that. Neither does Psychopy, for that matter. Of course, you *can* do it, but it’s not going to be incredibly easy.
Perhaps the easiest way to work is to use a List that repeats until the end of trial. In it there’s just a single slide, with duration of something like 10 ms. Prior to the slide, put in an inline that checks how much time has passed since the last change. Think of the two images not as two independent loops, but simply as something with an ON time and OFF time. So let’s say you have this loop go every 10 ms, and for the RSVP images, that’d become:
0 à RSVP ON
10 -> no change
20
..
100 à RSVP OFF
110 à no change
..
150 à RSVP on
And so on.
Right? That’s assuming you did the normal terminology of duration + ISI = SOA (stimulus onset asynchrony). But I see you don’t, because you cannot have images appear every 250 ms with interstimulus interval > 600, so I don’t know what that means. Anyway, whatever your exact timing, the trick is to make a smaller loop that can check for the passage of time in accordance of both intervals, and then change the stimulus field accordingly.
Best,
Michiel
//Michiel Spape
//Associate Professor
//ICI / CCBS, University of Macau
--
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To unsubscribe from this group and stop receiving emails from it, send an email to
e-prime+u...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/e-prime/6768477d-8406-4b6a-8d51-a4432a7c5ad2n%40googlegroups.com.