Adjusting length of trial based on performance

[Rachel S.]

I am working on a program that does the following:

Participants are presented with a fixation cross for 500ms, followed
by a fixation cross and 2 words (one to the left of the fixation cross
and one to the right). Then, a string of "X"es with either a "C" or
"O" in the middle replaces one of the words. The participant's job is
to indicate which letter they see by pressing C or O on the response
box.

If the participant gets 3 trials in a row incorrect and/or does not
respond before the next trial begins during 3 trials in a row, how can
I have e-prime adjust the presentation time of the string of "X"es so
that they are presented longer? And then, once they get 10 trials in a
row correct, how can I reduce the presentation time of the "X"es? In
other words, I would like to be able to adjust the presentation time
of the "X"es throughout the program based upon correct and incorrect/
no responses. Any thoughts on how to do this would be much
appreciated.

Thank you,
Rachel

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