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Thread: Random content in jump trials

  1. #1
    Join Date
    Nov 2005
    Posts
    3,318

    Random content in jump trials

    [edited from support email]

    I want participants will get feeback about how they respond to stimuli (i.e., whether their response is correct/incorrect). I can using the jumping function and get it to display either an incorrect or correct message depending on their response. But what I'd like to do is to have the system select at random from a number of alternative messages to display. For example, rather than always displaying "correct", I want to display "great", "wonderful", "awesome", etc., and I want to display them at random.
    First I tried to "rand(~BAD,~AWFUL, etc.)" in the stim field on trial
    997 (which is the trial that is skipped to when incorrect response is made). I also tried making a text file of the incorrect messages and call it with $badfb.txt (also placed in the stim field on trial 997).

    But in both cases, what happens is that the FIRST time a word is selected from the list, it is selected at random. So each participant will get a randomly selected positive or negative feedback feedback word. But then it is repeated every time thereafter. So it does not randomly select a word from the list each time the list is called. So participant #1 may get BAD or AWFUL or TERRIBLE at random the first time they give an incorrect response, but each and every time they give an incorrect response thereafter, they're going to get the same feedback word.

    Am I missing something in the manual that describes how to do this specific thing? A rather tedious workaround would be to create 2 skip trials for each experimental trial (e.g., make a skip to 997 if response is correct and 998 if incorrect for trial #1, and a skip to 999 if correct and 1000 if incorrect for trial #2, and so forth). But that would be painful.

    Any help would be appreciated!

  2. #2
    Join Date
    Nov 2005
    Posts
    3,318
    You havenít missed a thing. The problem here is that DirectRT treats those 997, 998 etc trials as regular trials. And it determines the content of random stuff before the session begins. So while you can randomly choose the stimulus, it is then fixed. If you replay any particular trial, it would always turn out the same way (i.e., the randomness is never done on the fly). I just bounced a bunch of possibilities around in my head, but came up with nothing. I thing pain is the only solution until I can think of some other way, e.g., adding an on-the-fly randomization function.

  3. #3
    Join Date
    Jul 2006
    Posts
    10

    Possible solution

    I think I might have figured out how to do what I was looking to do. It's not perfect, but it seems to work....

    In this example, participants are shown 2-digit numbers and asked whether they are 'good' or 'bad' numbers (by pressing the 'G' or 'B' keys respectively). They get feedback telling them whether their responses are correct or incorrect. They learn to distinguish good from bad numbers across trials. Let's say I want to reinforce participants 80% of the time they give a correct response, and punish participants 20% of the time they give an incorrect response (i.e., participants will learn via reinforcement rather than punishment). I make trials 980-989 the feedback I will give for correct responses. 8 or these will say something like "GOOD JOB!". 2 of them will be blank. I make trials 990-999 the feedback I will give for incorrect responses. 8 of them will be blank and 2 will say something like "AWFUL!". For each experimental trial, I set the time field to randomly select one of either the 10 reinforcing feedbacks or 10 punishing feedbacks.

    Like this:
    rt:34<rand(980,981,982,983,984,985,986,987,988,989 ),48<rand(990,991,992,993,994,995,996,997,998,999)

    Say a 'good' number was shown in this trial. Direct RT will randomly select one of the 10 reinforcing feedbacks (8 say GOOD JOB and 2 are blank) if participants press the G key (coded as 34). Direct RT will randomly select one of the 10 punishing feedbacks (8 are blank and 2 say AWFUL) if participants press the B key (coded as 48). Because each experimental trial is unique, it should make a new random selection of feedback each trial.

    I can't 100% verify that this works, but based on my own testing, it seems to be doing the job. Any obvious problems with this?

  4. #4
    Join Date
    Nov 2005
    Posts
    3,318
    Clearly the work of a clever bunny.

    I would deduct points only for your efficiency in choosing the random numbers, no? i.e., as opposed to:
    Code:
     rt:34<rand(980-989),48<rand(990-999)

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