Delayed Matching/Non-matching to Sample

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About the task

 

The Marker 1 sound is played to signal the start of a trial. An object is shown in the centre of the screen (Phase 1). (Optionally, the subject has to touch this object; optionally, it can be rewarded for doing so.) The object vanishes, and a delay ensues. After this delay, the object is re-presented together with one or more other objects (Phase 2), heralded by the Marker 2 sound.

 

In delayed matching to sample (DMTS), the subject must touch the object that was shown first. In delayed non-matching to sample (DNMTS), it must touch the new object. (Both test the subject's ability to remember information about the first object during the delay; the matching/nonmatching option is typically used to account for or overcome a subject's species-specific natural tendency to select either familiar or novel stimuli.)

 

Correct responses are rewarded; incorrect responses are punished. Optional correction procedure: if correction is switched on, failed trials are repeated once (see below).

 

Configuring the task

 

RatBat_DMTS_Params

 

Maximum number of trials. When the subject has performed this number of trials, the task ends. (You may specify 0 for no limit, though you must specify a limit on the number of trials, the time, or both.)
Maximum time. When this time elapses, the task is terminated as soon as the current trial has finished. (You may specify 0 for no limit, though you must specify a limit on the number of trials, the time, or both.)
Maximum time to wait for a response. If the subject fails to make a response within this time, the subject fails the trial. (This time limit applies to Phase 1, if you require your subjects to touch the Phase 1 stimulus, and Phase 2, and the correction procedure if one is used.)
Time between trials. Specify a minimum and a maximum intertrial time (they may be the same). The actual time is chosen with a rectangular probability distribution within these values.

 

Must touch phase 1 stimulus. If this is selected, then the subject must respond to the Phase 1 stimulus in order to proceed to phase 2. If you choose this option, you may also choose whether or not the subject should be rewarded for touching the Phase 1 stimulus. If you do not want your subject to have to touch the stimulus, you must specify the Phase 1 stimulus duration instead.

 

Matching. If this is ticked, the task is delayed matching to sample. Otherwise, it's delayed non-matching to sample.
For DNMTS, the original object is shown together with one novel object.
For DMTS, too, the original object is shown together with one novel object (distractor).
Correction phase if subject fails Phase 2. Optionally, phase 2 can be repeated immediately (once) if the subject fails it the first time.

 

Stimuli. This shows the list of available stimuli. You cannot put a stimulus into the list more than once. Click Add and Remove to add/remove stimuli. You can also choose one of two methods for choosing the stimuli for each trial:
Cyclical. The program begins with a specified stimulus number and selects stimuli for each trial by working down the list, resuming at the start of the list if/when it runs out of stimuli to use at the bottom of the list.
Random. The program picks a set of stimuli to use at random on each trial. You will need to fill in "Try to avoid stimuli used in last X trials"; the program will try not to choose any stimuli that have appeared (or were scheduled to appear, in the case of failure at phase 1) in the last X trials.

 

It's your responsibility to ensure that enough stimuli are in the list!

 

Levels. On the right-hand side of the screen is the list of memory delays (delays between phase 1 and phase 2) that correspond to levels in the task. You may add, remove, or re-order the levels with the buttons next to the list. You may then choose the starting level, and the method by which the task chooses a level for each trial. (You can have the level fixed, or chosen randomly for each trial, or you can increase the level by one every X trials, or you can increase the level by one when X of the last 20 trials have been performed correctly. Set your chosen value of X in the box.)

 

Options for reward and punishment are set in the General Parameters section; visual objects are defined in the Visual Object Library.

 

Screenshots from the task

 

Phase 1

ratbat_DMTS_Screenshot1

 

Phase 2. DMTS or DNMTS? You just can't tell...

ratbat_DMTS_Screenshot2