subliminal priming

[vinz]

Hello group,

I am current running a subliminal ERP study. Everything is fine as far
as the implementation of subliminal stimuli is concerned but we are
experiencing problems with the triggers from E-Prime to the Neuroscan
station.

Specifically, we have noticed that any time E-Prime sends a trigger
relative to a slide presented for a time between 100ms and 20ms (we
don't have anything in between this two values, so I cannot be more
specific) the trigger is sent twice, also affecting the following
slide (presented for about 500ms).

For the sake of clearness, the event table in Neuroscan looks like
this:

1 3 3 7 7 1 |1| 3 |3| 3 7 7 3 3 1

instead of:

1 3 3 7 7 1 3 3 7 7 1 3 3 7 7 1

where '1' is the trigger code for the subliminal stimulus, and |1|,|3|
are actually doubled. In fact the latencies for the first 1 and the
second |1| are equal. The same happens for 3 and |3|.

Being most likely a problem caused by incorrect trigger settings in
the InLine procedures, here it is what we are using:

WritePort &H378,1
WritePort &H378,0

WritePort &H378,3
WritePort &H378,0

WritePort &H378,7
WritePort &H378,0

If anyone is familiar with E-Prime triggers and has a suggestion to
give, I would greatly appreciate.

Thank you,
vinz.




On Aug 17, 9:19 am, liwenna <liwe... at gmail.com> wrote:
> Hey,
>
> I looked around a bit and I think the link in this page downloads a
> estudio file with subliminal exposure in it:http://www.docstoc.com/docs/5417962/Instructions-for-running-the-E-Pr....
> It's part of some book... and it also mentions some other usefull
> things. I think there really isn't all that much special to the design
> of a subliminal task... simply make the exposureduration on the
> primeslide really short (dependent on the exact nature of your task)
> and ussually you'll want to show a mask right after your prime but
> this is, again, dependent on the nature of your task. Then consider
> options like enabling preloading and disabling showafter (all should
> be explained in the mentioned chapter in the user-guide), and make
> sure that your hardware is actually capable of subliminal
> presentation.
>
> Greetz,
>
> liwenna
>
> On Aug 17, 8:25 am, Kim Janssens <kim.jansse... at gmail.com> wrote:
>
> > Hello liwenna,
>
> > Thank you for your fast reply: the advice on the refresh rate is really
> > helpful! If I come across any specific problems when building, I will post
> > my question again.
>
> > greetz,
> > Kim
> > ps: do you know where i could find an example of experiments designed for
> > subliminal priming? they could help me on the way..
>
> > 2009/8/15 liwenna <liwe... at gmail.com>
>
> > > Hello Kim,
>
> > > Perhaps you could elaborate a bit on what part of designing the
> > > experiment you need help with.
> > > In general I think you should start with reading chapter 3 and
> > > appendix A of the user guide (top of my head), which deal with timing
> > > issues, obviously important for subliminal priming. Only other thing
> > > that I can think of now is the monitor issue... make sure that you use
> > > a monitor (when doing the experiment) that is actually capable of
> > > subliminal-range exposure time i.e. has a sufficiently high enough
> > > refresh rate.
>
> > > I'm guessing that you're relatively new to e-prime (forgive me if I'm
> > > wrong there). I think it's the most easiest if you simply start
> > > building and post back here with problems that you encounter along the
> > > way.
>
> > > Good luck with it!
>
> > > liwenna
>
> > > On Aug 14, 2:20 pm, kimio <kim.jansse... at gmail.com> wrote:
> > > > Hello group,
>
> > > > I want to design an experiment in eprime in which I want to show the
> > > > participants a set of pictures and subliminally prime them with a word
> > > > in between the pictures.. Does anyone have any experience with this?
> > > > All help is welcome...
>
> > > > thanks,
> > > > Kim
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