Hi, Hisham -

I’m trying to simultaneously play an mpg file on one side of the screen and a set of letters (as a picture file) at a rate of one per second on the other side of the screen. The pupose is to measure a subject’s ability to resist the distraction of the movie while attending to a letter task.

In experimenting, I’ve also noticed that I can’t get two sets of letters to display in different portions of the screen at the same time. If both are linked to the same block and trial, they display alternately.

My attempts to solve the problem have involved creating one block, one trial, and two events, one with the movie and the other taking letters from a stimulus list.

Any suggestions?


How many movies do you have to play? Is it one that will be played continuously throughout the entire experiment? Is it a different movie for each trial?

If you want two different picture files to show up on the screen at the same time, you need two different events. The first picture event will need to be configured to “keep stimulus invisible.” This is under the “presentation options” tab in the picture settings dialog. The second (last) event will have this turned off, and it also must not erase the screen before presenting the stimulus, as this would erase any stimuli displayed before it (i.e. the one you want to show up at the same time).

If you are using stimulus lists, you will need a separate stimulus list for each event, as only one item is pulled from the stim list per trial. If you are using trial variables for the location, you will need a value for each event (or two separate trial variables).

How the movie is configured depends on whether it is one long movie or a bunch of short movies. If it’s one long movie, you will need to configure one event prior to your letter trials that is configured to keep playing after the trial ends. If it’s one movie per trial, you will need to configure the movie to stop playing when the trial ends.

I know these aren’t step by step instructions. If any of it isn’t clear, I’ll be glad to walk you through it.



Hank, your suggestions were really helpful. I am now able to play a movie and see the list of letters, and present two letter or word lists simultaneously. I’m still having trouble with the speed that two tasks run, when one is a movie and the other is a list of letters, The letters should take about 87 seconds to present at the rate of 1 letter per second (from a list of 87 letters in a stimulus list). The mpg is also about 87 seconds long, and should play without interruption, as one event, as the letters are presented, one per second. I’ve tried every combination I could imagine, and the best result I can get is either 1) the first letter hangs where it is and only advances to the next letter after the movie has played entirely, or 2) the letters scroll at a normal pace and the movie rips by at 10X speed. I’m sure it’s a matter of finding the right combination of stimulus presentation options for the timing, but I haven’t struck it yet. Thanks for your help.


If the movie is 87 seconds long, then you will want it in an event that occurs before all of the letter presentation events. It needs to be configured to continue to play beyond the end of the trial, AND you have to set it to load all stimuli prior to the start of the experiment (if I remember correctly).

At the moment, I don’t have a clue why it would play so fast. Are you on a Mac or PC?



I’m on a PC. I must confess I don’t know how to load an event before the experiment starts.


Loading Stimuli


I found it in options. That solved the problem of the mpg playing too fast. Progress is being made. Thanks.


I used the advice you gave to rkooken about pictures presented simultaneously on the screen. I followed your advice but it still didn’t work. My problem is, I want to present a lot of separate events in a trial e.g. (1) a photo (which I want to present by itself) and then (2) a face. I want the face to appear with a scale (attractiveness scale) but I don’t want this to affect the photo presentation (1). How can I do this?
Does this only work if you want all the events in a trial to be selected as “invisible” except the final one?


Here is a post that should be able to help you: http://community.cedrus.com/showthread.php?t=800