Design that loops a visual discrimination task while waiting for keyboard input?

[Colton Perry]

Hi all, I hope this isn't something I could have easily figured out by a 
good Google search, I just haven't been able to find the correct search 
terms to get what I'm going for here. 

I'm trying to implement a design that's a bit beyond my understanding (most 
of my experience with e-prime has been mostly pretty straight-forward 
linear presentation stuff). To boil it down to a single trial, I'd like to 
present a simple visual search/discrimination task alongside a set of 
verbal instructions. So for example, at the onset of a trial, a text 
display would appear providing instructions for a primary task to be 
performed outside of e-prime (these tasks are performed on a motorcycle 
infotainment system). A short time after the onset of those instructions, 
the visual discrimination task would begin. So, leaving the instructions on 
the display, a letter would appear. If this is a key letter, the 
participant would respond with a key press (well, a foot pedal mapped to a 
key press "b", but a key press to Eprime). If it's not a key letter, then 
the participant does nothing and the letter disappears. The part I'm not 
sure how to accomplish is that after they respond with a key press, I need 
the discrimination task to repeat itself on average every 5 seconds (so 5 ± 
2s) while the text display with the instructions remains the same. After 
the participant completes the primary task on the motorcycle, a researcher 
would then press a key to end the trial and move on to the next set of 
instructions. 

So it would look something like this:

Primary task instruction onset
--- key letter appears > foot pedal response > key letter disappears, 
record RT
--- foil letter appears > no response > foil letter disappears after a 
given time, record response if incorrect
--- repeat randomly
--- Primary task completed > research presses key > record total trial time
Primary task instruction onset
etc.

Does this make sense? Please let me know if I need to provide more 
information. I'll keep trying different things in the meantime. Most of my 
experience with Eprime has been in the gui interface rather than the inline 
commands, so I'm pretty inexperienced on that end, but I'm definitely 
willing to learn. 

Thanks in advance for your time, 

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