ABA glossary
Paired-stimulus preference assessment
Also called forced-choice assessment, paired-choice assessment
Definition
A preference assessment in which items are presented two at a time and each item is paired with every other item; items are ranked by the percentage of times they were chosen when offered.
In plain words
Because every item is compared directly with every other item, the paired-stimulus (forced-choice) format gives a clear, detailed ranking from most to least preferred. It suits learners who can choose between two items but struggle to scan a larger array. The trade-off is time: with many items the number of pairs grows quickly (8 items means 28 pairs). Each item's selection percentage is the number of times it was chosen divided by the number of times it was offered, times 100.
Example from a session
The RBT presents bubbles and a puzzle, one on her left and one on her right, and says "Pick one." Jun reaches for the bubbles and gets brief access. On the next trial she presents the puzzle and a car, switching left and right positions across trials as the data sheet shows. After every pair has been presented, bubbles were chosen 4 of 4 times offered (100%), so bubbles rank highest.
For BCBA candidates and supervisors
Analysts counterbalance item positions to detect and limit position bias, and decide in advance how to handle trials with no selection or with an attempt to take both items (typically block the second reach and re-present, or record no choice). The format can produce problem behavior in learners for whom item removal is aversive, and edibles may be over-selected if mixed with toys, so separate assessments are sometimes run. A paired-stimulus ranking predicts reinforcer effectiveness reasonably well for top items but less so for middle and low items.
Often confused with multiple-stimulus without replacement, single-stimulus preference assessment
Paired-stimulus offers exactly two items per trial and pairs every item with every other. MSWO offers the whole array at once and removes each chosen item. Single-stimulus offers one item at a time and records approach. Paired-stimulus gives the most complete ranking but takes the longest.
Exam tip
"Two items at a time" or "forced choice" means paired-stimulus. If asked how to rank items, use selection percentage (times chosen ÷ times offered), not the raw number of choices.
Can you spot paired-stimulus preference assessment in a scenario?
Practice RBT B.1 with exam-style questions and instant feedback.