No subject

[sung0015]

Dear Colleague:

I have an experiment which would present a fixation point at the center of
the screen, and then at either x position=66% or 34% the stimulus (image
file) would present.

Two questions:
1. How could  I present a stimuli for a certain period of time (i.e., 49
msec) but the exp won't go to next trial until the subject makes a
response?
Note:
Now i put 49 msec as the presentation time but the program goes to the next
trial without waiting for the response!

2. While presenting the image file stimulus, could I still present the same
fixation point at the center location? If so, how should I do it?
Note: I tried the "transparent" option but then the fixation point shifts
with the image file!

I appreciate your help!

Yung-Chi Sung
Department of Educational Psychology
Center for Cognitive Sciences
Educational Development and Research, Office of Education, Medical School
USA