problem with extended response collection

[Tobias]

Hi,

i wanna set up the following experiment: A stimulus appears for 250
ms. Participants are to respond to that stimulus either during
presentation of that stimulus or any time after, when a response
screen is shown until the participant reacts. If the participant
reacts during stimulus presentation, the response screen should not be
displayed.

I did this as follows:
(1) I made a slide that has a duration of 248 ms (should round up to
150 as I use a screen of 100 Hz). I set the time limit to "(infinite)"
and the end action to "(none)".
(2) After the slide follows an Inline Script with this content:
"if c.getattrib("search.resp") = "a" or c.getattrib("search.resp") =
"l" then goto Label1"
(3) Then follows a slide that serves as a response screen. It has an
infinite duration (-1) and "terminate" as an end action.
(4) The next element ist the Label1

This works quite well for most of the trials. If the particpant
presses a or l during stimulus ("search") presentation, the inline
will make e-prime jump the the label and not call the response screen.
If the particpant does not press the button during presentation, the
response screen appears until a button is pressed.

However, sometimes, like about 5% of the trials, participants would
have to press twice. That is, even though they pressed a button during
stimulus presentation, the response screen appears. My first guess is,
that this is because in these rather seldom cases, the participant
presses the button in the few milliseconds between stimulus offset and
response screen onset. Is that possible? How can I circumvent this
problem? Have you had a similar problem?

Your help is most appreciated!

Best,
Tobias

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