Catch trials

[bdnc]

Add a feature to specify a set of catch items that are repeated for each participant. This provides a measure of the consistency of that participant over time.

Describe the solution you'd like
When defining the study, the admin defines a set of specific items that will be catch items. This would mean that these items must be included in every participant's item set, and has the advantage that all the participants respond to the same catch items. This would also provide a set of items that are common to all participants and provide a measure of inter-rater reliability.
For each catch item, there should be a suitable number of intervening trials between the first and the second presentation. This could be defined as a minimum number of trials (which could be fixed and probably doesn't need to be user definable).
For these catch items, both responses need to be flagged as being for catch items and also for whether the response corresponds to the first or second presentation.

Describe alternatives you've considered
Alternatively, the admin could just define the number of catch items that each participant should have and the system (randomly) selects which specific items they will be. This would mean that different participants have different catch trials.