How to represent an identical random experimental session (case 3490)

First off, I've been racking my brain trying to figure out how I can represent an experiment to a given subject in session 2 , that had been initially randomly presented in session 1. Any and all help will be utilized and appreciated!

So, I am randomizing between-subject 4 tasks, and within each task, between-subject the presentation of 16 trials (stimuli). Also, before the tasks begin, stimuli is randomly created by pairing text-labels with images. So, basically, a given experiment is in entirety random pairings and presentation (i.e. each subject completes a somewhat different experiment).

What I need to do is somehow have medialab (and directRT) "remember" a given participant's experiment, so that I can re-present the identical experiment in session 2 (approximatly 2 weeks after session 1). Clearly the experiment will "end" in session 1, but does anybody know if we can recall a given session to re-present the identical experiment?

At first, I thought "absolutely nope." Especially with MediaLab. I could imagine ways but given how much randomization you are talking about, these "ways" would be very cumbersome. Especially the part where you are randomly pairing images with the labels (not even sure how you are doing that! --in MediaLab??).

But THEN I saw you were using DirectRT also. Here, there *might* be a way. If you create all you randomization for a given session using a DirectRT input file, DirectRT saves a COPY of that input file with all of the randomization outcomes in it--in the same folder as your original input file. You could take THAT input file (i.e., the copy) and administer that to your second subject. It will be identical in all respects because it will be the same input file that the first subject received. That's because if randomization functions are used in a DirectRT input file, it's actually the COPY that is used in the session--not the original.

But again, if it's mostly MediaLab content, then it gets trickier to do a design like this. Does this help at all?

I looked over your files. I'm sorry I wasn't clear on the type of randomization used. Apparently it applies only to random value functions as described in this link--

[url]www.empirisoft.com/directrt/help/directrt_using_random_values.htm[/url]

However, there still might be some way to get at this. Have you looked to the log data files as a source for duplicating the input file that created it? It should have all of the stimuli presented and could easily be sorted by the "order" column. With a macro it might be possible to automate the conversion of the log data into original input. Is that a possibility? Either that, or possibly converting the input file to one that uses the random value functions described above? I think what would be ideal is if DirectRT had the option to save the log data file also in the format of the original input file.

Hi Blair, thanks for the response.

I like the idea of using the rand() function and have been playing with it over the weekend. Is it possible to randomly choose a value (either a text label or an image) [I]without[/I] replacement? That is, I'd like to make sure values are evenly matched and presented (i.e. 8 of one group via text labels is presented and 8 of the other group as well).

If that's possible via the rand() function I think I would be able to use that and the problem would be solved (re-present the [I]copy[/I] of the log file).

If not, I would be interested in automating the process of taking from log files in the original experiment and creating a new input file from that. Could you shed some more light on that procedure? I am unsure how we could achieve this.

Mmm. Those randomization functions don't have a without replacement option like you get with the use of stim files. That makes me wonder if you colud simply enter the stimuli into stim lists and draw them from there randomly without replacement? You could also repeat the stimuli that are selected if you need to. I'm guessing the sessions are not back to back? That would be great because you could use the "repeat" stimulus function to create the duplicate task. Limit is that it only works within the current session, so you need to have both subjects particpating as if they were one.

More abpout that here:
[URL]http://www.empirisoft.com/directrt/help/directrt_stim.htm[/URL]
(see Using Randomly Selected Stimuli Again)

And the sample with elaborated instructions:
[URL]http://www.empirisoft.com/directrt/help/directrt_samples_of10_using_previous_stim.htm[/URL]

But yes, transforming log files into input files is certainly also an option--a fairly basic text manipulation routine or an Excel macro could probably take care of that. Before getting into that though, is stimlist functionality of possible use? And do you or anyone you know have any basic programming skils? If so, I could give you some direction in transforming the log files.

What we are currently using is the stimlist feature; however, the sessions are not back-to-back, so that wouldn't be useful for the time two session (in which the participant should have an identical experience as time one).

As to manipulating the log files, I believe I could program myself given a bit of instruction.

What method of programming do you like to use? Do you know VB? It's nice and quick for text manipulation.

I haven't used VB, I've done some HTML / Java programing in the past...If VB is similar than I should be able to tackle it. However, do you have an example of transposing a log file to a new input file?

Hi gh0strider18!

Just checking to see if you needed any help with this programming or if you had figured something out.