extended response time with second slide to be terminated

[Tobias]

Hi there,

I have been puzzled by the following problem and would like to present an 
easy solution.

I want to present a search slide for exactly 200 ms and then to present a 
second 'response slide' for 5 seconds. If participants press a button 
during the response slide, the response slide should vanish, the trials 
should be ending and the next one starting. By using the extended response 
time I can accomplish reactions being recorded for the entire duration of 
the response slide (I set the time limit to 5200 ms).

The problem here was the "end action". If I use "terminate", a very early 
response will also terminate the search slide thus resulting in shorter 
presentation times than 200 ms (this is especially problematic since we are 
doing EEG here).
If I set it to "none" and the response slide to "-1", it works as intended 
only if participants react after search slide offset. If the respond 
before, they would have to press the button twice.

So what I did was to introduce a one-line script between search slide and 
response slide and a label "Label1" after the response slide:
if searchslide.RESP <> "" then goto Label1

This script checks if there was any response for the search slide and if so 
it jumps to Label1. If not, the response slide will follow and will be 
terminated by any button press.

The only concern I have is what happens if participants respond during the 
execution of the script (which should be less than a ms, but who knows...).

I would appreciate if this whole procedure would be possible without 
scripts and labels. This paradigm is quite common in experimental 
psychology I believe.
Maybe PST will implement it one day.

Tobias

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