Timing Coroutines

Comments

• sebastiaan

  June 2020

  Hi @Mira ,

  You cannot reduce the preparation time (although it varies depending on the backend, so you could try another backend to see if that reduces it). But you can reduce the variability of the preparation time, so that you can better control how long the experiment takes. To do so, you can add an inline_script to the start of the trial_sequence. In the Prepare phase, note when the preparation starts:

  prepare_onset = clock.time()
  

  Then, in the Run phase, calculate how long the Prepare phase of all items in the trial_sequence took, and subtract this value from a fixed intertrial interval (ITI ). Of course, this interval should be a bit higher than the maximum prepare duration that you see in your experiment, because you can only make the intertrial interval longer, not shorter!

  ITI = 1000  # Fixed intertrial interval
  run_onset = clock.time()
  prepare_duration = run_onset - prepare_onset
  print('prepare duration: {}'.format(prepare_duration))
  if prepare_duration > ITI:
      print('Warning: preparation took longer than ITI')
  else:
      clock.sleep(ITI - prepare_duration)
  

  An even fancier solution is to determine beforehand exactly when each trial should start, and then wait at the start of the trial_sequence until that moment. With such 'non-slip timing' you have perfect control over the duration of the experiment; but this is generally only useful in an fMRI experiment.

  Cheers,

  Sebastiaan

  
  
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