Meeting a criterion
CRITERIONMET terminating condition
Habituation phases are generally set up as a trial (or set of trials) occurring within a loop. CRITERIONMET is a special loop terminating condition for habituation that is based on looking-time reduction from a basis window. How the basis window is chosen, and what reduction in looking time it takes to consider the child to be habituated, are defined at the beginning of a protocol as habituation criteria. The CRITERIONMET terminating condition, whenever it is evaluated, checks whether these habituation conditions have been satisfied.
Below is an example of the basic structure of a habituation protocol.
Using the habituation settings above, here is an example of how the basis window and criterion would be calculated by BITTSy across trials.
In this example, note that the target criterion window time (i.e. the maximum time a participant can look during a window and be considered to have met habituation) can change when a new basis window is identified, when BASISCHOSEN is set to LONGEST. The first window in which the child's total looking time is less than the current target criterion time is the window of trials 5+6. After trial 6, when this window is evaluated, CRITERIONMET is true, the loop terminating condition is met, and the loop will no longer repeat. The habituation phase will end, and execution will move on to the next phase of the protocol.
It is important to note that, like all loop terminating conditions, CRITERIONMET is only checked when the loop step is reached - that is, after each time the contents of the loop have been fully executed (see loop terminating conditions for an expanded explanation.) This means that if the loop contained two trial starts and trial ends, CRITERIONMET would only be evaluated after even-numbered trials. This does not prevent BITTSy from evaluating and identifying criterion windows based on the habituation settings in the protocol. But it does mean, in this case, if a criterion window was identified that ended with an odd-numbered trial, one additional habituation trial would be run before the loop would end. For this reason, it is generally recommended to only define one trial within a habituation loop, and if stimuli vary across trials, to define their cycling via selection from groups. (See the example protocols page for examples of setting up simple and more complex habituation phases.)
Alternate terminating conditions (did not habituate)
Many times, you want not only a terminating condition for when the participant habituates, but also a point at which the phase would end even if habituation is not reached. For example, you might want to end a phase either when the child habituates, or after 20 trials, whichever comes first.
In this case, you essentially set up two potential endings for the phase:
In a loop clause, if you have two different UNTIL statements, with a carriage return between them, they are treated as if they are linked by an OR condition (see this section for all available options). This would mean it would end either if the criterion was met or if it had already looped through 19 times (after the first one, so UNTIL 19 TIMES means there would be 20 times total).
Whichever terminating condition is met first, execution will progress to the next step: it is not possible to skip to a different step or phase based on which condition is met. Generally, this means that the post-habituation test phase of a typical habituation experiment would be shown to all participants, whether or not they habituated. When generating a habituation report from the event log of a test session, it is marked whether the participant habituated (i.e. met the CRITERIONMET condition rather than the alternate one) so that participants who did not habituate can be recorded as such, and excluded from analyses of looking time in the test phase.
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