subliminal priming

[kimio]

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

[liwenna]

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

[Kim Janssens]

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 <liw...@gmail.com>

[liwenna]

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-Prime-program.
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...@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...@gmail.com>

[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...@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....

[ben robinson]

maybe you you'd want to sleep for 10 ms before sending the "WritePort &H378, 0"... just a suggestion, won't necessarily fix it.

ben

[vinz]

Thank you Ben,
I will try it out tomorrow, and then let you know.

Thank you again.
vinz.

On Aug 18, 3:25 pm, ben robinson <baltimore....@gmail.com> wrote:
> maybe you you'd want to sleep for 10 ms before sending the "WritePort &H378,
> 0"... just a suggestion, won't necessarily fix it.
> ben
>

[vinz]

Hi Ben,

tried to add 'Sleep x' in between the two 'WritePort' but
unfortunately it did not do the trick.

It actually did with 'Sleep 40', but considering my stimuli (type 1)
last about 6-7ms that delay is obviously infeasible.
I can still use the data (getting the event table, correcting it with
a custom script in matlab and then epoching in Neuroscan according to
the modified event table file) even though, as you may understand, it
is kind of a pain..

In fact, given that there must be a way to get the triggers sent right
and neat in the first place, it feels quite annoying to have to
correct them after each session.

Once again, any help on how to send triggers for short-lasting stimuli
(we are experiencing problems for any length<100ms) would be much
appreciated.

Thank you,
vinz.

[Peter Quain]

to get 6-7ms duration your monitor must be running at ~ 142Hz -
that's a fast refresh! You must be using canvas (I assume, because
you are using WritePort commands). Anyway, say your monitor is set to
100Hz. You should be able to copy from offscreen canvas at the start
of a refresh, and follow the copy command with a writeport then Sleep
for 7ms, then zero the port, and fit it all in the 10ms refresh. I
thought Neuroscan equipment liked pulsewidths of a few ms, and my old
lab had no worries with 7ms duration pulses.