Multiple stimulus without replacement
In a multiple stimulus without replacement (MSWO) preference assessment, several items are presented together, and each chosen item is removed from the array before the next choice.
The RBT places an array of items, often five to eight, in a line in front of the client and asks them to choose one. After brief access to the chosen item, that item is not returned. The remaining items are rearranged, often by moving the leftmost item to the right end, and the client chooses again. This continues until all items are chosen or the client stops choosing.
The order of selection produces a preference hierarchy: the first item chosen is ranked highest. Results are often combined across several rounds (for example, three to five) by giving each item a score based on its rank or by calculating the percentage of trials it was selected when available. MSWO gives a ranking similar to the paired stimulus format in much less time, which is why it is commonly used.
The client must be able to scan an array and choose one item, so MSWO may not suit everyone. Edibles and leisure items are often assessed separately, because edibles tend to be chosen ahead of leisure items when they are mixed. Large activities that cannot be placed in an array or removed quickly are a poor fit. RBTs follow the procedure for rotating positions so that a choice is not just a preference for a particular location on the table.
Example and non-example
| Example | An RBT places six snacks on a tray. The client picks pretzels first; the RBT removes the pretzels, shifts the others, and the client then picks raisins, and so on until the tray is empty. |
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| Non-example | Putting the pretzels back on the tray after each choice so they are available again is multiple stimulus with replacement. |
Don't confuse it with
| Multiple stimulus with replacement | MSWO removes each chosen item, producing a full ranking; MSW returns chosen items, so a top item can be chosen again and again. |
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| Paired stimulus preference assessment | MSWO presents the full array at once; paired stimulus presents two items per trial. |
Test yourself
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Question 1In which preference assessment are two items presented at a time and the client chooses one of them?
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D: Paired stimulus. In a paired-stimulus (forced-choice) assessment, items are presented two at a time, and each item is paired with every other item. The client's choices are used to rank the items.
- A: Single-stimulus assessment presents one item at a time.
- B: MSWO presents an array of several items at once.
- C: A free-operant assessment makes all items available at the same time with no trials.
Task B.1 · 40-hour curriculum section D
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Question 2An RBT places six items in a row in front of a client. The client picks one, plays with it briefly, and the item is then left out while the remaining items are rearranged for the next trial. Which preference assessment is this?
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D: Multiple stimulus without replacement. In MSWO, a selected item is not put back. The client chooses from fewer items each trial, and the order of selection produces a ranking.
- A: In MSW, the chosen item is returned to the array for the next trial.
- B: A paired-stimulus assessment presents only two items per trial.
- C: A free-operant assessment has no trials or selections; items are freely available.
Task B.1 · 40-hour curriculum section D
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Question 3A client chooses from an array of five toys. After each brief play period, the RBT puts the chosen toy back in the array with the others for the next trial. Which preference assessment is this?
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B: Multiple stimulus with replacement. Returning the chosen item to the array on every trial is what defines multiple stimulus with replacement (MSW).
- A: A paired-stimulus assessment presents two items per trial.
- C: Single-stimulus assessment presents one item at a time.
- D: In MSWO, the chosen item is left out of the array.
Task B.1 · 40-hour curriculum section D
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On the RBT exam
This term belongs to task B.1 Preference assessments in content area B, Behavior Assessment, which is 8 of the 75 scored questions.