Tutorial: StimLists (4/21)


…\DirectRT\samples\1 bare bones\stimlist seq.csv

…\DirectRT\samples\1 bare bones\stimlist truerand.csv

…\DirectRT\samples\1 bare bones\stimlist rand.csv


Rather than specifying a specific stimulus on every trial (as in the previous three samples), you can opt to request that the stimulus be chosen from a stimulus list or StimList. StimLists are text (.txt) files that you create with any text editor that simply list stimuli. This can be especially handy if you want to randomize the stimuli that fill particular positions in your input file. There are three types of StimLists.

In the first example, notice that the input file named "stimlist seq.csv" is identical to the last one except that instead of identifying specific stimuli in the Stim column, we have replaced the image names with &pics. In the stim folder is a file called pics.txt. This file simply lists all of our images just as we would have entered them in the stim column. The & symbol tells DirectRT that you want to draw stimuli from this list sequentially-i.e., in the order they appear in the text file. Try running the session and see how it looks. We've labeled each image so you can see that they are appearing sequentially as specified in the list.

Now, open the input file named "stimlist trurand.csv." Notice that it's the same as the last except that instead of the & symbol, the StimLists are preceded by the % character. This tells DirectRT to randomly select a stimulus from the list. Try running the session. Notice that since this is True Random selection, some of the images may appear twice or more. If you take a look at the data file created by this input file, you'll see that the Stim1 column tells you which image was selected and presented.

Finally, take a look at the input file named "stimlist rand.csv." This time, we use the $ symbol. This again tells DirectRT we're using StimList, but that we want the stimuli selected randomly without replacement. DirectRT will make sure all of the stimuli are used before it re-randomizes the file and starts over.

As an exercise, try adding a stimulus or two to the ..\DirectRT\samples\1 bare bones\stim\pics.txt StimList in any text editor. Try entering an image that's located somewhere else on your hard drive, such as c:\images\mypic. Or add a text item such as ~I love pizza!, or a text file such as #instruct1. Place the additional stimuli anywhere in the list, save it, and re-run any of these session and see what happens.