RSVP stream: varying target position?

Coding
1

Hi, I’m looking to build an RSVP stream with a set length of 9 items. However, I want to vary the target location within the stream, so that it may be presented as either item 5, 6, 7, or 8 in each trial. I am looking to also counterbalance the target position. What would be the best way of doing this using the coder?

2

Something like this code skeleton:

# assuming the number of trials is a multiple of 4,
# create a balanced list:
target_locations = [5, 6, 7, 8] * (number_of_trials/4)

# randomise its order:
numpy.random.shuffle(target_locations)

for trial_number, trial in enumerate(trials):
    this_target_location = target.locations.pop()

    for stimuli in range(9):
        if trial_number + 1 == this_target_location: # NB 0 vs 1 based
            # show the target
        else:
            # do whatever else
3

Thanks for this! Would you mind explaining how this works:

4

Can you be more specific? This is just an outline of the sort of structure your code would need, it won’t work by itself.

i.e. you need a loop for your trials (ideally a TrialHandler psychopy.data - functions for storing/saving/analysing data — PsychoPy v2023.2.3), then within each trial, a loop for displaying the stimuli. But without seeing your own code, it is hard to be give more useful detail.