Target position

[liwenna]

Hello Ashraf,

E-prime does not offer the possibility to control target positions
relative to each other not in terms of 'place one target a centimeter
left to the other, and not in terms of place 6 targets in a circle).
The only way to position targets is by positioning each target
separately. In the slide object you can place multiple targets and
give each target an x (horizontal) and an y (vertical) position, this
can be done in eather pixels from the top left corner or percentages
of the total screen size.

For your setup you should make an slide object with 7 textboxes: 6 in
the circle and 1 to the left or right. For the circle letters figure
out the correct x and y positions either by simply trial and error and
controlling with a set triangle. Yet I also think it should be
possible to simply calculate the desired x and y positons if you know
what the dimensions of your screen are, how big your textboxes are and
how big the circle should be. (do not forget to tell e-prime the
dimensions of your screen first however... find display properties
under the square with the e-prime E at the top of your experiment
tree). For the target letter-textbox the x position (left or right)
should be drawn from a list that holds the value for x (in a variable
called targetposition for instance) and is set to the value for left
(ie 25%) or rigth (75%) both in half of the trials. In the properties
of the targettextbox set the y value to center (assuming that it
shoudl appear in the vertical middle of the screen) and set the x
value to [xtargetposition] to make it refer t1o the variable with 25%
or 75% in it.  The content of the textboxes (i.e. the letters that
make up the target and distractors) should also be drawn from a list.
Make a list with 7 variables: distractor1 distractor2 etc and target:
and place your letters into this list. In the properties of the 7
textboxes do not fill in a text but fill in [distractor1],
[distractor2], etc. For each of the trials the textboxes will now take
their content from (the same level of ) the list.

Alternatively, you could make the distractor circle arrays in a
separate program (perhaps paint, it is more easy I think with
photoshop, Gimp or another programs that offers working in multiple
layers). Then you can use an image like this one:
http://www.mathsisfun.com/geometry/images/degrees-360.gif, and place
it in a layer. In a new layer you can then place your letters and
delete the circle layer and save the image to use in in e-prime. (as
an imageobject in your slide). You would need to make quite a bunch of
these images however in order to not have the same circle of
distractoritems repeat too often.

I hope that this info will help you start your experiment.

Good luck and best regards,

liwenna

On Jul 30, 12:45 am, ashraf ashraf <ash2003r... at yahoo.com> wrote:
> . I want to  make of six letters in E-prime , and I want to present target letter appears  in one out of six possible positions in a circle and a distractor letter  presented to the left or right of the circle,
> how can i maniplute Target position and distractor position .
>  
> I read in some papers properties of stimuli as " The task display consisted of
> a circle (1.61 radius) of six letters centered at fixation, plus aperipheral distractor letter, presented to the left or right of the circle, 1.41 away from the nearest circle letter. Each of the
> circle letters subtended 0.61 by 0.41, and the distractor letter subtended 0.81 by 0.51. "
> what do   these numbers mean and how could I control  it with E-prime
>  
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