Tutorial: Compound Screens (10/21)
This is a tricky but pretty powerful concept. Open the input file and see that it's the same as the last except that we have added a new stimulus to each trial. Just before each image appears, we've added an image called scale1. This is a graphic of a scale that we'd like to have appear on the same screen as the reaction time stimulus (i.e., the faces).
To do this, we insert scale1 as a stimulus and locate it where we want it. We've told DirectRT here to place it at x = .5, y = .95, which is telling it to place the center of the image half way across and 95% of the way down the screen.
The trick? Notice the Time column for the scale image. It's 0! This tells DirectRT to create the screen but not to display it! Why would want to do this?? Because if on the NEXT screen we tell DirectRT to NOT clear the last screen, then this previous screen will serve as a BACKGROUND for the next stimulus.
Sounds complicated but it really isn't. All this means is that by using 0's in the Clear value of the Loc column you can have layers upon layers of stimuli appending to the same screen. If you set the Time value of any of these stimuli to 0, then they will appear at the same time the subsequent stimulus appears.
I hope this is making sense.
Finally, notice that the on the last two trials (before the debriefing) the clear value in the Loc column of $pic is set to 0 instead of 1. Notice how when you run the session, the adjective stays on the screen when the picture appears. As an exercise, try setting the Time value of one of these adjectives to 1000 instead of 0. See that this makes the adjective appear for 1000ms before the image appears, but still remains on screen because it is never cleared in any subsequent Loc column.