implement change blindness flicker paradigm

[melissa]

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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