E-Prime newbie Task Events query

[oskar.m...@gmail.com]

Hi everybody,

Long-time lurker, first-time poster. E-Prime noob question, but haven't been able to find the answer in any of the official (or unofficial!) channels.

I'm currently setting up an ERP-experiment using E-Prime (v. 2.0 Professional) for stimulus presentation, which includes a list that randomizes between two audio stimuli, a standard and a deviant. I have the randomization occurring at the level of file selection (more specifically, I have a SoundOut object in the proc, which loads the file [Tone].wav, where the attribute [Tone] can take on either of the values "standard" or "deviant", thereby loading the corresponding sound file).

Now, I can use "Task Events" in the SoundOut object in order to write a binary value to my parallel port (thereby signalling our EEG-equipment that the stimulus is being presented), with a specific value at Stimulus Onset, and back to 0 at Stimulus Offset. But I cannot for the life of me figure out how to write two different binary values depending on whether the randomization happens to choose to load the standard or the deviant tone.

I've watched E-Prime's official How To video on Task Events, and there is a semi-cryptic remark to the effect that I can change the value in the "Enabled" box (which defaults to "Yes" or "No" in a drop-down menu) in order to specify some sort of criterion for a Task Event.

What I have now is a single Stimulus Offset (writing 0 to parallel port), and two different Stimulus Onsets (writing 256 and 128, respectively, to the parallel port) as Task Events on the same SoundOut object, but I cannot figure out how to control it so that the 256-value is triggered by the standard stimulus, and the 128-value triggered by the deviant stimulus. Manually entering the attribute values ("standard" and "deviant") or the loaded sound-files ("standard.wav" and "deviant.wav") into the "Enabled" box doesn't work.

Any help would be much appreciated!

Best,
Oskar MacGregor

[David McFarlane]

I know this is an old thread, but I cannot resist providing an answer
because it is so simple ...

Add a column (attribute) to the List that provides your sound file
names, and put your desired ERP output codes there. E.g., call the
column "ERPCode", and put 256 for the standard stimulus, and 128 for the
deviant stimulus.

Then in the Task Events for your stimulus, use a Source of "(custom)",
and a Custom of "[ERPCode]" -- i.e., just use an attribute reference for
Custom. That's all!

BTW, I like to use double Task Events for this sort of work. I set one
to trigger with OnsetTime (Delay of 0) to output my desired value, and
then another to trigger with a delay from OnsetTime (e.g., Delay of 20)
in order to reset the output.

-- David McFarlane

On 2015-11-29 4:54 PM, oskar.m...@gmail.com wrote:
> Long-time lurker, first-time poster. E-Prime noob question, but haven't been
> able to find the answer in any of the official (or unofficial!) channels.
>
> I'm currently setting up an ERP-experiment using E-Prime (v. 2.0 Professional)
> for stimulus presentation, which includes a list that randomizes between two
> audio stimuli, a standard and a deviant. I have the randomization occurring at
> the level of file selection (more specifically, I have a SoundOut object in the
> proc, which loads the file [Tone].wav, where the attribute [Tone] can take on
> either of the values "standard" or "deviant", thereby loading the corresponding
> sound file).
>
> Now, I can use "Task Events" in the SoundOut object in order to write a binary
> value to my parallel port (thereby signalling our EEG-equipment that the
> stimulus is being presented), with a specific value at Stimulus Onset, and back
> to 0 at Stimulus Offset. But I cannot for the life of me figure out how to write

> two /different/ binary values depending on whether the randomization /happens to
> choose to load the standard or the deviant tone/.