problem with extended response collection

[Michiel Spape]

Hi,
If you're right (and I guess it is possible), then you might try setting offset sync of 1) to none, and onset sync of 3) to none. That way you might get some screen-tearing artefacts, but the time between them should be microseconds (rather than milliseconds) - making it terribly unlikely that subjects respond at that time.

But, I don't think this is necessarily the problem. I have a feeling (but correct me if I'm wrong) that time limit of infinite, with duration of 248, might go wrong. How, for example, is E-Prime to know that a late response (after the 248) is for 1) rather than 3)? My suggestion:
1) As you say (with time limit = infinite), but also with jump label (label1) to 4. End 
2) makes little sense (search.resp?) Is Search the slide in 1)? If so, then it should be without getattrib (i.e. not reading from list, but from object 1).
3) Slide, as you say, except _without response collection_ (since 1 is doing that).
4) As you say.
So, without any code, for once, the stimulus is shown for 250 ms, if participant reacts during that time, they don't see 3. Unless you don't want the stimulus to be presented shorter (perhaps you do EEG?). In which case it might be a bit more difficult:
5) Short inline: ExtendedStim.Duration = 250 - Slide1.Duration 'slide1 being whatever you named 1
6) ExtendedStim is a slide that is just a copy (control+drag) of 1). Except it doesn't have keyboard input or collect responses.

Anyway, the nice thing is that the response is always collected by the same object now, which is at least my preferred way of coding E-Prime.
Does that help?
Best,
Mich

Michiel Spapé
Research Fellow
Perception & Action group
University of Nottingham
School of Psychology
www.cognitology.eu


-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of Tobias
Sent: 10 February 2011 18:30
To: E-Prime
Subject: problem with extended response collection

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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