Mworks eye problem

Hi Chris,
The problem I’m having is that occasionally m-works fixation point windows will not be triggered by the eye input despite the fact that the eye position is within the image window. I’ve attached some eye traces, it’s a slightly convoluted figure so I apologize for that. The traces show the eye position error relative to the target position, downsampled at 100Hz. The blue curves are hit trials, the red curves are trials where no selection was made. The black line shows the error limit (6 deg image window, or 3 deg radius). The eye has to remain within this limit for 700ms, or 70time steps in the plot. In the plot, I’ve aligned everything to the last 750ms of the trial.

I’ve highlighted two particular trials (with thicker lines). As you can see, in both cases, the eye is within the window for the required duration, but in one case it is not registered as a hit trial. I believe this is because the image window is not triggered (and so eye_in_sample_image_window is not updated) unless a saccade is detected, but I don’t have further evidence for this. It’s also possible that I have a bug in my task, although this error doesn’t happen systematically.

The .mwk file is somewhat large, so I can’t email it to you. Let me know if you want to take a look at it and I’ll find some way to share it. Any thoughts?

As always, thanks a lot for your help.


Attachment: compare.png (30.8 KB)

Hi Rishi,

Thanks for taking the time to make this plot. It looks to me that during the bad trial (the thick red line), the eye was pretty much at the exact center of the fixation point (i.e. zero error) until ~680ms. Also, unlike all the blue lines, the thick red line appears to start the trial already within the fixation window; that is, I don’t see it crossing the black line at any point. Am I reading the plot correctly? (A second plot with only the highlighted lines would be helpful.)

It still might be helpful for me to look at the raw data file. Can I give you a USB stick to copy it to?


Hi Chris,
Yes, you’re reading it right. The reason you can’t see it enter the window
is because the trial is longer and I aligned it to the end of the selection
period (so if we go back in time, we can see when/how it entered the
window). I’ll gladly give you the raw data on a flash drive, and thanks for
all your help!

Hi Chris,
I think I’ve figured it out. It’s a bug in the task related to what we were
talking about this morning. I reset the “eye_in…” variables before he is
allowed to make a decision, and again every time he “exits” a decision, so
rapidly following eye movements are not captured by the trigger. (see
attached figure if the text is unclear). Anyway, I’m sorry, this was my
fault all along, and thanks for chatting with me this morning to help me
figure it out!

Attachment: eyeproblem_solution.png (3.74 KB)

Great! I’m glad I was able to help.