Multiple Stimuli Without Replacement

Multiple Stimuli Without Replacement (MSWO)

Multiple stimuli without replacement (MSWO) is a popular method of preference assessment.  It used a great deal with communication training, for preferences need to be identified and ranked with each new session.  This method is more complete than a simple pre-task choice because it incorporates many items in an array.  Though not exactly as quick as a pre-task choice, it is efficient enough that it may be conducted several times per day. The MSWO begins with a group of items, called the array.  Before it begins, several items must first be identified for the item array.  While there is no set amount, a manageable array is about 6-8 items.  The client then select the items from the array, one by one, which places them in an order of preference.  The clinician records the items in the array and the order in which they were selected by the client. Steps in the MSWO Preference Assessment
  1.  Items are identified for the array
  2.  Items are presented to the client one at a time.  If it is an object, the client may play with it for up to 30 sec.  If it is a familiar food, it is shown to the client but the client does not eat it.
  3.  The array is presented to the client and she makes a selection using a verbal cue, such as “Choose one.”
  4.  After about 30 seconds, the item is taken away from the client and the cue is represented for the next trial.
  5. Data are collected on the order of the selections.  This order then is regarded as the client’s preference, the most preferred item being the was that was picked first and the least preferred is the item that was picked last.

MSWO Preference Assessment Procedure Checklist

View or download to review the steps in a MSWO preference assessment.

Multiple Stimuli With Replacement

A variation of this method is multiple stimuli with replacement.  For this method, the selected items is placed back in the array and the items that were not selected are replaced with new items.