implement change blindness flicker paradigm

[David McFarlane]

Melissa,

Look at the InputMask.IsPending topic in the online E-Basic 
Help.  See that the RespWait.InputMasks.IsPending() test will detect 
whether RespWait has timed out (e.g., set Time Limit to 40000) or has 
received a response, as I mentioned earlier.  So you may use that in 
inline code to end your flicker loop.

Many ways to implement this loop.  E.g., put a label like 
FlickerLoopLabel in front of your flicker stimuli, and some inline 
right after the stimuli, such as

If RespWait.InputMasks.IsPending() Then Goto FlickerLoopLabel

Alternatively, use a List (e.g., FlickerList) to run your loop.  Set 
the FlickerList to run for some long time, put your flicker stimuli 
into a List Procedure (e.g., FlickerProc), and in inline right after 
the stimuli do

If Not(RespWait.InputMasks.IsPending()) Then FlickerList.Terminate

More generally, first work through Chapter 4 of the User's Guide for 
some exercises on using inline code.  And get familiar with the 
online E-Basic Help.

-- David McFarlane, Professional Faultfinder


>David,
>
>Thank you.  That solves the problem of getting the response time while
>the flickering is occurring.  However, I am still having issues with
>how to create a loop that will loop the two stimulus objects back and
>forth for either 40 secs or until user input.  First off, how would I
>implement this type of loop?  With an inline object?  Secondly, guess
>I could have the loop end when the wait object ends or unless there is
>user input?  I am not quite sure how this would be done in Eprime.
>
>Thank you for the help!
>Melissa
>
>On Jun 21, 1:36 pm, David McFarlane <mcfar... at msu.edu> wrote:
> > Melissa,
> >
> > Stock reminder:  1) I do not work for PST.  2) PST's trained staff
> > takes any and all questions 
> athttp://support.pstnet.com/e%2Dprime/support/login.asp, and they
> > strive to respond to all requests in 24-48 hours (although current
> > estimates are more like 10 days) -- this is pretty much their
> > substitute for proper documentation, so make full use of it.  3) If
> > you do get an answer from PST Web Support, please extend the courtesy
> > of posting their reply back here for the sake of others.
> >
> > That said, here is my take...
> >
> > Yes, that is possible, to a point.  However, if you use an input mask
> > on the Slide and just rapidly re-run that Slide, you will have some
> > trouble with RTs.  That is because the input mask will not be armed
> > in the short intervals between each running of the Slide object, and
> > if a response comes in during those intervals then it will be
> > missed.  And the more rapidly you cycle through your Slide, the
> > greater the effect.  (I know, because I ran into this with an
> > experiment a few years ago.)
> >
> > For something like this, better to use "extended response" (see
> > Appendix C of the User's Guide that came with E-Prime).  Implement
> > your flicker loop however you like, and just before your flicker loop
> > add a Wait object.  Set its Duration to 0, give it an appropriate
> > input mask, and set the Time Limit to (infinite), or a time limit
> > that you choose.  Set End Action to Terminate or (none), as seems
> > appropriate.  Now the input mask from the Wait object will run over
> > all the iterations of your flicker loop and will catch a response at
> > any time.  If you want the flicker loop to then react to the
> > response, use some inline code such as (assuming you name your Wait
> > object RespWait)
> >
> > If Not(RespWait.InputMasks.IsPending()) Then ...
> > If RespWait.RT <> 0 Then ...
> > If RespWait.RTTime <> 0 Then ...
> > If RespWait.RESP <> "" Then ...
> >
> > Finally, given that the Wait object takes care of getting the
> > response, I would probably dispense with the two-state Slide (which
> > requires even more inline code) and just use a pair of ordinary
> > stimulus objects for the flicker loop.
> >
> > -- David McFarlane, Professional Faultfinder
> >
> >
> >
> > >I am trying to implement the classic flicker paradigm for a change
> > >blindness study.  I would like to oscillate between a picture and its
> > >mask for 40 seconds or until a participant hits a button.  I think the
> > >best way to do this would be to use one slide object and oscillate
> > >between slide states (1 state for the picture, 1 state for the mask)
> > >in order to keep track of RT for the user response.  Is this possible?
> >
> > >Thank you,
> > >Melissa

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