positioning of slide e-objects

[hitzig at yorku.ca]

I'm working on a visual task using slide objects in which I need my stimuli to
appear 3.4 inches from the fixation point (a + sign in the center of the
screen) but I'm having problems getting it to appear correctly.

A cue should appear either on the left or right of my fixation, and then the
target stimulus should appear on the opposite side at an equal distance.  My
resolution is 640X480 and my cue and stimuli are set to the 200th and 400th
pixel.  However, the stimuli are not appearing on equally on either side (the
stimuli on the right are closer to my fixation than when they appear on the
left side of my fixation).

In addition, my stimuli are appearing .5x larger than they should be on the
screen when the task is being run.

Does anyone know how to set slide objects to appear at a specific distance from
the center with regards to screen resolution?  Or does anyone know of any good
resources that may help me with this problem.   ANy suggestions or help would
be greatly appreciated.  Thank you.

Sander Hitzig
York University - Dept. of Psychology
hitzig at yorku.ca