Contingent Branching, etc.

[Susan Campbell]

I¹m not sure if someone else has answered these questions already, but here
are (non-definitive) answers to at least some of them.

On 10/21/02 11:48, "Catherine Ortner" <catherine at psych.utoronto.ca> wrote:
> I have a few questions:
> 
> Does anyone know anything about contingent branching (see page 160 in E-Prime
> User's Guide)?
> I have a set-up where in the first part of the task, participants have 3
> response options (1, 2 or 3).  According to which one they select, the task
> then proceeds to one of three lists.  I am using the following script after
> the first trialproc:
> 
> If Allbuttons.RESP = "1" Then
>   List1.Run
> ElseIf Allbuttons.RESP = "2" Then
>   List2.Run
> Else List3.Run
> End If
> The problem is that I am getting an error message when I try to run it:
> "Factor error: Invalid context in list 1" (or list 2, or list 3, according to
> which response I make on the first part of the experiment).  I'm not really
> sure what that error message means?  When I delete my script, the whole thing
> works fine (it's just that then I get the three possible lists run
> sequentially). Perhaps I have not set-up the different levels of the task
> correctly - should the first part, and then the script, and then the three
> lists, all come on the same timeline in the first trialproc?
> 
It looks like the newer version of E-Prime (1.1) has a slightly different
structure for lists; they take a context variable.  This isn't documented in
the User's Guide, possibly because it's new.  Putting in "List1.Run c"
instead of "List1.Run" should fix that (c is the default, current context).

> 
> My next question follows from this: once participants have completed either
> list1, 2 or 3, I then need the task to go back to the first screen (where they
> have the three response options).
> 
I would do this by placing the branch within a list that repeats the
procedure containing the branch as many times as you want it to (or for
however many seconds).

> I would like to set up a counter on the screen that will continuously display
> cumulatively how many 'points' the participant has.  Any tips on how to get
> started on this?
> 
This would probably just involve setting a global variable in the User
script tab and updating it when the participant does something.  To display
it, you could use slides for your text displays and set a text box object in
one corner that you could update from a script.

> Finally, I need to set up something that will enable me to deduct points from
> the participant at predetermined intervals (probably on a variable ratio
> schedule).
> 
I don't have any great ideas on this one, sorry.  If you know the program
isn't going to be doing anything else at the time, you can just deduct
points from an inline script.  Otherwise, this may require more complex
scripting, and I'm not entirely certain how well E-Prime handles background
scripts.

Hope this helps,
Susan Campbell
STEP Project 
Carnegie Mellon