Pausing experiment execution

Interactive elements and commands can pause experiment script execution.

Pause experiment until a valid keypress

We’ll use a wait command on a Key element to pause experiment script execution until the participant presses a valid key.

instructions
  1. Create a Key element named "keypress" that is validated by a press of the F or J key.
  2. Call the wait command on the "keypress" Key to pause the trial until the participant presses a valid key, in this case the F or J key.

@// Type code below this line.
@
@// Remove command prefix
@PennController.ResetPrefix(null)
@
@newTrial("experimental-trial",
@    newAudio("fish-audio", "2fishRoundTank.mp3")
@        .play()
@    ,
@    newText("fish-sentence", "The fish swim in a tank which is perfectly round.")
@        .print()
@    ,
@    newImage("fish-plural", "2fishRoundTank.png")
@        .print()
+    ,
+    newKey("keypress", "FJ")
+        .wait()
@)

Pause experiment until audio playback finishes

The wait command on the "keypress" Key pauses the trial until a valid keypress. However, you might want to pause the trial until audio playback finishes.

We won’t actually use this option in the BasicTutorial experiment, but we provide its code as a reference.

Optional - Think about what the code should look like, and then check to see if you’re right!
(Hint: You’ll need to refer back to the "fish-audio" Audio)

Pause trial until audio playback finishes
  1. Remove the wait command on the "keypress" Key.
  2. Refer back to the "fish-audio" Audio with getAudio.
  3. Call a wait command on the "fish-audio" Audio.

@// Type code below this line.
@
@// Remove command prefix
@PennController.ResetPrefix(null)
@
@// Experimental trial
@newTrial("experimental-trial",
@    newAudio("fish-audio", "2fishRoundTank.mp3")
@        .play()
@    ,
@    newText("fish-sentence", "The fish swim in a tank which is perfectly round.")
@        .print()
@    ,
@    newImage("fish-plural", "2fishRoundTank.png")
@        .print()
@    ,
@    newKey("keypress", "FJ")
-        .wait()
+    ,
+    getAudio("fish-audio")
+        .wait()
@)

Pause experiment until a valid keypress or audio playback finishes

The experiment pauses until a valid keypress, meaning that if a participant presses a valid key before audio playback finishes, it ends audio playback early because when the experiment unpauses, the trial (and experiment) ends.

If we want audio playback to finish before the trial ends, we have to also pause experiment execution at the Audio element. However, simply calling a wait command on the "fish-audio" Audio will not work as intended.


@// Type code below this line.
@
@// Remove command prefix
@PennController.ResetPrefix(null)
@
@// Experimental trial
@newTrial("experimental-trial",
@    newAudio("fish-audio", "2fishRoundTank.mp3")
@        .play()
$        .wait()
@    ,
@    newText("fish-sentence", "The fish swim in a tank which is perfectly round.")
@        .print()
@    ,
@    newImage("fish-plural", "2fishRoundTank.png")
@        .print()
@    ,
@    newKey("keypress", "FJ")
@        .wait()
@)

The wait command here actually prevents the printing of the "fish-sentence" and "fish-plural" elements until the "fish-audio" Audio finishes playing, because PennController executes experiment scripts from top to bottom.

To get around this, we can use the getAudio() function to refer back to the "fish-audio" Audio at a later part of the script, and call the wait command there.


@// Type code below this line.
@
@// Remove command prefix
@PennController.ResetPrefix(null)
@
@// Experimental trial
@newTrial("experimental-trial",
@    newAudio("fish-audio", "2fishRoundTank.mp3")
@        .play()
@    ,
@    newText("fish-sentence", "The fish swim in a tank which is perfectly round.")
@        .print()
@    ,
@    newImage("fish-plural", "2fishRoundTank.png")
@        .print()
@    ,
@    newKey("keypress", "FJ")
@        .wait()
@    ,
$    getAudio("fish-audio")
$        .wait()
@)

But calling the wait command here doesn’t work as intended either! This experiment “freezes” if the participant presses a valid key after audio playback finishes.

The wait command on the "keypress" Key pauses the experiment until a valid keypress, at which point PennController evaluates the wait command on the "fish-audio" Audio. This command, like all wait commands, pauses the experiment until a certain event occurs.

However, by default PennController starts waiting for the event after the wait command is evaluated. In other words, since audio playback finished before the wait command on the "fish-audio" Audio was evaluated, it doesn’t qualify as an event that unpauses the experiment. As a result, the experiment pauses without a way to ever unpause it.

The solution is to add the "first" parameter, which tells PennController to pause the experiment until the event has occurred. If the event occurs before the wait("first) command is evaluated, when the wait("first") command is actually evaluated the experiment pauses and immediately unpauses, as if it didn’t pause at all.

instructions
  1. Refer back to the "fish-audio" Audio with getAudio.
  2. Call the wait("first") command on the "fish-audio" Audio.

@// Type code below this line.
@
@// Remove command prefix
@PennController.ResetPrefix(null)
@
@// Experimental trial
@newTrial("experimental-trial",
@    newAudio("fish-audio", "2fishRoundTank.mp3")
@        .play()
@    ,
@    newText("fish-sentence", "The fish swim in a tank which is perfectly round.")
@        .print()
@    ,
@    newImage("fish-plural", "2fishRoundTank.png")
@        .print()
@    ,
@    newKey("keypress", "FJ")
@        .wait()
+    ,
+    getAudio("fish-audio")
+        .wait("first")
@)