A preference assessment is a structured method for identifying which items, activities, or forms of attention a learner finds most motivating, so a therapist can use them as reinforcers during teaching. The goal is simple: replace guesswork with data. Common formats include the multiple stimulus without replacement (MSWO) method, paired choice, single stimulus, and free operant observation, each suited to different learners and situations.
TL;DR:
- Preference assessments should be repeated frequently, with quick checks before sessions, to capture shifts in learner preferences that may occur within days.
- Using the multiple stimulus without replacement method often yields reliable rank orders with fewer trials, making it suitable for regular reassessment.
- Starting with single stimulus or free operant formats is advisable for new learners to prevent unreliable data from confusion or frustration.
- Rotation of item positions during assessments helps minimize position bias and ensures genuine preference data.
- Confirming that a highly ranked item functions as a reinforcer requires an individual response check, as preference alone does not guarantee behavior increase.
Table of Contents
- Why Run a Preference Assessment in ABA Therapy?
- What Are the Types of Preference Assessments in ABA?
- How Do You Conduct a Preference Assessment Step by Step?
- How Do You Interpret Preference Assessment Results?
- Common Pitfalls When Running a Preference Assessment
- How Building Block Resolutions Trains Preference Assessment Skills
- What the Research Actually Supports
- Get Hands-On Guidance for Your Child’s Preference Assessments
- Sources
- FAQ
Why Run a Preference Assessment in ABA Therapy?
Guessing what motivates a child rarely works for long. What excites a learner on Monday might fall flat by Friday, and a reinforcer chosen on instinct can quietly stall progress for weeks before anyone notices. Running a preference assessment replaces that guesswork with direct observation, giving the therapy team a working list of items and activities a learner actually wants to work for.
Timing matters. Buildingblockresolutions typically recommends a preference assessment before starting a new teaching program, before completing a functional behavior assessment (FBA) or behavior intervention plan (BIP), and any time engagement noticeably drops during sessions. Preferences shift with mood, age, and even the weather, so routine rechecks belong in the plan, not just the initial intake.
Who runs it matters too. A Board Certified Behavior Analyst (BCBA) typically designs the protocol and interprets results, while a Registered Behavior Technician (RBT) or trained caregiver often administers the actual trials under that oversight. This division of labor keeps the process both practical and clinically sound.
A few things to confirm before the first trial:
- Informed consent from the parent or guardian, with the purpose of the assessment explained in plain language.
- A brief caregiver interview to build the initial item list, since families know a child’s routines better than any checklist.
- A calm, distraction-minimized space where rapport comes first. Practitioners in the field describe preference assessments as collaborative and ongoing exercises that build trust rather than one-off tests.
- A plan for who reviews and signs off on the results.
Skipping this groundwork is one of the most common reasons preference assessments produce shaky data later.
What Are the Types of Preference Assessments in ABA?
Not every learner fits neatly into one assessment format, and choosing the wrong one wastes time or, worse, triggers frustration. Each method balances speed against precision differently.
- Free operant assessment. Multiple items are placed in a natural environment, and the therapist simply records engagement time or approach frequency without removing anything. This format works well for learners who become upset when a preferred item is taken away, since items stay available rather than being removed between trials.
- Single stimulus assessment. One item is presented at a time, and the therapist notes whether the learner approaches or ignores it. It suits learners with very limited choice-making skills or minimal communication, since there is no comparison required.
- Paired stimulus (paired choice) assessment. Two items are presented side by side across repeated trials, and the learner’s selections build a full rank order. It delivers the most precise hierarchy but takes the longest. Ranking a set of just eight items through every combination can require 28 separate pairings, which is worth knowing before you schedule a fifteen-minute slot for it.
- Multiple stimulus with replacement (MSW). Several items are presented together, the learner picks one, and then all items (including the chosen one) go back into the array for the next trial. It is faster than paired choice but can inflate the apparent value of the first few items picked, since nothing is ever removed.
- Multiple stimulus without replacement (MSWO). Several items are arranged in a row, the learner picks one, and that item is removed before the next trial begins. This format has become something of a clinic default because comparative research shows it often produces similar rank orders to paired stimulus with far less administration time.
Pro Tip: If a learner is brand new to choice-making trials, start with single stimulus or free operant. Jumping straight into paired choice with a learner who has never had to pick between two items often produces noisy, unreliable data.
Here is what a basic MSWO session looks like in practice: five items are lined up on a table, spaced evenly apart. The therapist says, “Pick one,” and records the selection. That item is removed, the remaining four are re-spaced to close the gap, and the therapist repeats the prompt. This continues until one item remains, producing a full rank order in roughly five to seven trials instead of the dozens required by paired stimulus.
How Do You Conduct a Preference Assessment Step by Step?
Fidelity starts before the first trial. Build your item list first, either through a direct caregiver interview or a structured tool such as the Reinforcer Assessment for Individuals with Severe Disabilities (RAISD). Aim for five to eight candidate items spanning categories: edibles, toys, sensory items, and social attention.
Set up the environment with minimal distractions and the items visible but not yet accessible. Then work through these steps:
- Arrange items in a straight line or semicircle at equal distance from the learner.
- Use a short, consistent script: “Pick one” or “Which one do you want?”
- Allow brief access for consumables (roughly 5 to 10 seconds) to avoid early satiation, since prolonged access to edibles can reduce their effectiveness as reinforcers later in the session.
- Rotate item positions between trials so a learner’s selection reflects genuine preference rather than a habit of reaching left or right.
- Run enough trials to cycle through the full item set at least once, ideally twice for confidence in the ranking.
Quick fact: a short MSWO check at the start of a session, using just two or three top items, can be completed in a few minutes and is often more useful for day-to-day planning than waiting for a full quarterly reassessment.
On your data sheet, mark three things for every trial: which item was selected, how long access lasted, and whether it was the learner’s first or later choice in that round. This makes graphing the rank order afterward straightforward, whether by hand or in a spreadsheet.
If a learner shows escalating frustration, stop the trial immediately, offer a brief break, and consider switching to a free operant format for the remainder of the session rather than pushing through.
How Do You Interpret Preference Assessment Results?
A preference hierarchy tells you what a learner likes. It does not, on its own, tell you what will actually change their behavior, and confusing the two is one of the most common errors in the field. A preference assessment identifies candidate reinforcers, but a separate reinforcer assessment is what confirms whether a preferred item genuinely increases a target behavior when it is made contingent on that behavior.
Once you have the rank order, plot it visually, whether that is a simple bar chart of selection frequency or a percentage-of-trials graph.
Before building a reinforcement system around a top-ranked item, run a brief single-case check: deliver the item contingent on a target response for a handful of trials and watch whether that response increases. If it does not, the item is preferred but not functioning as a reinforcer for that particular behavior, which happens more often than most new clinicians expect.
Once confirmed, integrate the results practically:
- Populate a token economy or choice board with the top three to five ranked items.
- Rotate reinforcers within a session to prevent the satiation that dulls even a learner’s favorite item.
- Revisit the hierarchy whenever a previously reliable reinforcer stops working, since that is often the first sign preferences have shifted.
Data collection habits matter here too, and Buildingblockresolutions’ guide on data collection in ABA therapy walks through how to turn raw trial notes into charts a supervising BCBA can actually use.
Common Pitfalls When Running a Preference Assessment
Even well-trained clinicians run into the same handful of snags. Most are fixable in the moment rather than requiring a redo.
- Position bias. If a learner consistently picks whatever is on the left, rotate item placement every trial and randomize the array rather than keeping a fixed order.
- Satiation with consumables. Long access windows burn out food reinforcers fast. Keep access brief and lean on approach or duration measures instead of full consumption.
- Problem behavior during trials. If a learner becomes upset when items are removed (as happens in MSWO or paired choice), pausing and shifting to a free operant format can reduce escalation while still revealing genuine preference patterns.
- Stale hierarchies. Formal reassessment every few weeks is reasonable, but a quick two-minute MSWO check before a session catches faster shifts that a monthly schedule would miss.
Pro Tip: Log every deviation from the standard protocol, including switched formats or shortened trials, in the session note. A supervisor reviewing a hierarchy months later needs to know whether the data reflects a clean assessment or an adapted one.
Whatever changes you make mid-assessment, tell the supervising BCBA and the caregiver. A hierarchy built on an adapted protocol still has value, but only if everyone using it knows the conditions under which it was collected.
How Building Block Resolutions Trains Preference Assessment Skills
Competent administration takes more than reading a protocol once. Supervisees at Buildingblockresolutions practice each format, single stimulus, paired stimulus, MSWO, and free operant, in role-play before running them with an actual client, and a supervisor confirms fidelity and initials the checklist before independent sign-off. This mirrors broader competency benchmarks used across the field, where graphing results and applying them to FBAs and BIPs count as advanced skills, not entry-level ones.
These skills map directly onto the BACB task list competencies around assessment and data-based decision making. With more than 20 years in the field, Buildingblockresolutions builds this training into how every RBT and BCBA on staff prepares to work with families.
What the Research Actually Supports
The evidence points somewhere most training programs undersell: the choice of method matters less than the discipline behind running it. MSWO’s efficiency advantage over paired stimulus is real, but a rushed MSWO with no position rotation produces worse data than a careful paired choice assessment done right. Conventional training often treats method selection as the hard part and administration fidelity as an afterthought. It should be the reverse.
The bigger gap I see is reassessment frequency. Clinics love a quarterly formal assessment because it looks tidy on a calendar, but a child’s preferences do not run on a quarterly clock. A two-minute MSWO check before a session catches shifts that a formal schedule misses entirely, and it costs almost nothing to run.
If you take one thing from this playbook, prioritize the brief, frequent check over the elaborate, infrequent one. Precision matters, but only after consistency is in place.
— Jennifer
Get Hands-On Guidance for Your Child’s Preference Assessments
Reading a protocol is one thing. Running it confidently with your own child, under a real behavior plan, is another. Buildingblockresolutions builds preference assessment directly into individualized ABA treatment plans, so families get more than a one-time list of favorite toys. They get a system that a BCBA maintains, updates, and ties to actual progress in communication and daily living skills.
Parent coaching sessions also walk caregivers through running quick preference checks at home, so reinforcement stays consistent between formal sessions. If you want a clear starting point, read the ABA therapy guide for parents and reach out to schedule an initial consultation.
Sources
For hands-on templates, the VCU Autism Center’s tip sheet offers practical flowcharts for classrooms and clinics. The ABAdegree glossary entry consolidates format definitions and decision rules in one place. For a field-oriented perspective on collaborative practice, see the Pressbooks chapter, and for empirical comparisons across methods, consult the PMC research article.
- Abadegree
- Use of preference assessments in the field of applied behavior analysis — Pressbooks
- Peer-reviewed comparisons of preference assessment formats — PMC article
- Preference assessment procedures for individuals with developmental disabilities — HCPBS (2018)
FAQ
What Are the Main Types of Preference Assessments in ABA?
The five most common formats are free operant, single stimulus, paired stimulus (paired choice), multiple stimulus with replacement (MSW), and multiple stimulus without replacement (MSWO). Each differs in setup, trial structure, and how precisely it ranks items.
What Is an Example of a Preference Assessment?
A common example is an MSWO trial: five items are placed in a row, the learner picks one, that item is removed, and the process repeats until a full rank order emerges in about five to seven trials.
Can an RBT Run a Preference Assessment?
Yes, a trained RBT can administer most preference assessment formats under the supervision and design oversight of a BCBA, provided they have demonstrated fidelity during training.
How Is a Preference Assessment Different From a Reinforcer Assessment?
A preference assessment identifies items a learner likes, while a reinforcer assessment tests whether delivering that item actually increases a specific target behavior. Both matter, since a preferred item does not always function as an effective reinforcer.
How Often Should Preference Assessments Be Repeated?
Formal reassessment every few weeks is common practice, but brief pre-session checks using top-ranked items can catch faster preference shifts that a longer schedule would miss.
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