Successful and unsuccessful trials
Last updated
Last updated
You might decide that you want to exclude particular trials from calculation of habituation. For example, you might wish to exclude any trial that has no looking at all. Or you might want to allow the experimenter to exclude individual trials at the time (say, if they felt the child was distracted by something in the room, such that the trial was not an accurate measure).
This can be done, and is part of the used within a trial. You have already learned how to denote end conditions that are "successful" and should let the trial be counted for habituation calculations - these are simply UNTIL statements. "Unsuccessful" end conditions are the same kinds - just with an UNSUCCESSFUL flag.
The above example would play the file "audiofile" until one of the following occurs:
You reach the end of the audio file
A look away is logged that exceeds 2 seconds (when the trial is started only when the experimenter judges the child is already oriented in the active direction, this requires that a look toward the stimulus has already been logged)
10 seconds have passed since the trial started and the child has not yet looked at all
The experimenter presses a designated key (X) to stop the trial
As with other , these conditions are treated as "whichever comes first". So, if the 3rd or 4th condition were met first, the trial would be unsuccessful. The trial would end at that point, and would not be counted as a trial for the purposes of habituation calculations, which depend on successful trials. (More precisely, this means that any window containing this trial would not be evaluated as either a potential basis window or criterion window.) If condition 1 or 2 were met instead, the trial would then end, and it would be counted.
Marking a trial as unsuccessful only excludes the trial from habituation calculations. It does not exclude it from being counted as one of a set number of trials, as in an alternate loop terminating condition. For example, if your phase is set up as
it repeats until either the criterion is met or the loop occurs 20 times - marking a trial as unsuccessful doesn't change the looping.
If you want to replace a no-look trial altogether, you could have another loop that loops the trial until a condition was met. Then the inner loop would do 2 trials if its condition wasn't met the first time, and the outer loop would still go the same number of times, getting you an extra trial for each trial that was not successful.
It is also worth noting that in the syntax above, not only does the trial not count if the child hadn't looked in 10 seconds, but it also ends at that point - that is, it does not continue to play the rest of the sound file. You could have it finish the trial anyway with the statement:
but that would mean that any looks that occurred after 10 second mark would still be ignored from the count of habituation, and yet would presumably influence the child nonetheless. We instead recommend that if you are ignoring a trial for non-looking, that the trial end at whatever point you make that decision.
Here, it ends and is marked as successful if the sound file ends and there were any looks during that time, or if the child looked and then looks away for 2 seconds. It is unsuccessful if the experimenter pressed the X key, or if there weren't any looks at all by the time the audio file ends.
What about if you want it to play the whole file, and only mark the trial as unsuccessful if they never look at all? For that, recall the setting defines the minimum look length that counts for looking time calculations. This is the smallest amount that can be logged, so "never looking at all" is anything less than the COMPLETELOOK value.