Updating trigger_flag in an array for a fixation point stimulus group

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1

Hi,

I’ve been working on implementing a functionality where multiple occluders are present, and fixation on one of the occluders for a set amount of time will remove the occluder.

I am using a stimulus_group of fixation_point stimuli as square occluders, and setting trigger_flag = onFixOccluders[${local_index}] for each occluder so that fixation on one of the occluders will update the relevant entry signaling fixation. However, it seems that the trigger does not work properly. I’ve searched around and it seems writing to a variable will only work if I give a variable name, and so a particular entry of a list won’t be writable – is this correct? If so, what do you think is the best way to setup something like this where I have multiple occluder fixation points and want to keep track of whether each of the occluders are being fixated on separately? I might have to change around the number of occluders so ideally it does not require manually defining a new fixation-tracking variable for each occluder, but I’m not sure if there’s a better way.

Here is the stimulus group definition in case it helps:

stimulus_group occluders {
    range_replicator (
        variable = local_index
        from = 0
        to = nOccluders - 1
        step = 1
        ) {

        stimulus/fixation_point occluder${local_index}(
            color = occluder_red, occluder_green, occluder_blue
            trigger_watch_x = eye_x
            trigger_watch_y = eye_y
            trigger_width = occluderSize
            trigger_flag = onFixOccluders[${local_index}]
            x_size = occluderSize
            y_size = occluderSize
            x_position = occludersX[${local_index}]
            y_position = occludersY[${local_index}]
            rotation = 0
            alpha_multiplier = occluder_alpha
            )

}

}

As always, thank you for your help!

2

Hi Hokyung,

I’ve searched around and it seems writing to a variable will only work if I give a variable name, and so a particular entry of a list won’t be writable – is this correct?

Yes, that’s correct. Changing this is on my to-do list, but it’s a non-trivial project, and I’m not sure when I’ll get to it.

If so, what do you think is the best way to setup something like this where I have multiple occluder fixation points and want to keep track of whether each of the occluders are being fixated on separately? I might have to change around the number of occluders so ideally it does not require manually defining a new fixation-tracking variable for each occluder, but I’m not sure if there’s a better way.

Unfortunately, I think defining a new fixation-tracking variable for each occluder is your only option. But you can still define the occluders using a range replicator and, with a little extra work, keep onFixOccluders updated with the current fixation state of all occluders. Please see the attached example.

Cheers,
Chris
occluders.mwel (1.7 KB)