A preference assessment is a structured way to find out which items or activities a learner likes most, so the team can use them as potential reinforcers. There are five common types in ABA: free operant, single stimulus, paired stimulus (forced choice), multiple stimulus with replacement (MSW), and multiple stimulus without replacement (MSWO). This guide explains each type with examples and when to use it. Conducting preference assessments is task B.1 on the RBT Test Content Outline (3rd ed.).
Why Preference Assessments Matter
Reinforcement only works if the learner actually wants what you offer. Preferences change from day to day, so RBTs often run brief preference assessments before or during sessions. Remember: a preferred item is only a reinforcer if it increases the behavior it follows. See the overview in Preference Assessments in ABA.
The 5 Types of Preference Assessments
| Type | How it works | Pros | Cons |
|---|---|---|---|
| Free operant | Learner has free access to items; you record time spent with each | Fast, natural, nothing is taken away | Less precise ranking |
| Single stimulus | One item at a time; record approach or engagement | Good for learners who cannot choose between items | Can show many items as “preferred” |
| Paired stimulus (forced choice) | Two items at a time; learner picks one; every pair is presented | Clear ranking of items | Takes longer with many items |
| MSW (with replacement) | Several items in an array; chosen item is put back | Quick; shows if one item stays on top | May hide second- and third-choice items |
| MSWO (without replacement) | Several items; chosen item is removed and the rest are re-offered | Clear ranking, faster than paired stimulus | Removing items may upset some learners |
Free Operant Preference Assessment
The learner moves freely among items for a set time, often 5 to 15 minutes, and you record how long they engage with each one. Read the free operant definition.
Single Stimulus Preference Assessment
Items are presented one at a time, and you record whether the learner approaches or engages with each. It is helpful for learners who have trouble scanning or choosing between multiple items.
Paired Stimulus (Forced Choice) Preference Assessment
Two items are shown at once and the learner chooses one. Each item is paired with every other item, and items are ranked by how often they were chosen. Read the paired stimulus definition.
Multiple Stimulus With Replacement (MSW)
Several items are placed in a row. After the learner chooses one, it is returned to the array and the other items are replaced or rearranged. Read the MSW definition.
Multiple Stimulus Without Replacement (MSWO)
Several items are placed in a row. The learner chooses one, that item is removed, and the remaining items are presented again until all have been chosen or the learner stops choosing. Read the MSWO definition.
Tips for RBTs Running Preference Assessments
- Use the type and items listed in the learner’s plan.
- Rearrange item positions so choices are not driven by location.
- Give brief access to the chosen item before the next trial.
- Record every choice and share results with your BCBA.
- Repeat often, since preferences shift with mood, time of day, and satiation.
Grab our free preference assessment packet with ready-to-use data sheets.
Frequently Asked Questions
What are the types of preference assessments in ABA?
The five common types are free operant, single stimulus, paired stimulus (forced choice), multiple stimulus with replacement (MSW), and multiple stimulus without replacement (MSWO).
What is the difference between MSW and MSWO?
In MSW the chosen item is returned to the array. In MSWO the chosen item is removed, which produces a ranking of all items.
Is paired stimulus the same as forced choice?
Yes. Paired stimulus and forced choice preference assessments are the same procedure.
Which preference assessment is least likely to cause problem behavior?
The free operant assessment, because no items are taken away from the learner.
How often should preference assessments be done?
Often. Many teams run brief assessments daily or before sessions, with more formal assessments as directed by the BCBA.
Keep learning: Download our free RBT data sheets, checklists and study tools, or see everything that changed for RBTs in 2026.
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