ABA glossary
Momentary time sampling
Also called MTS
Definition
A discontinuous method in which an interval is scored only if the behavior is occurring at the exact moment the interval ends. It can over- or underestimate and easily misses brief behaviors.
In plain words
With momentary time sampling, the observer only needs to look at set moments, such as every 2 minutes when a timer vibrates. Whatever is happening at that instant is recorded, and what happens between checks is ignored. That makes it the least demanding method and lets an RBT keep teaching or observe several learners. It works best for behaviors that last a while, such as being in seat or engaged; it is poor for brief or rare behaviors, which are easily missed between checks.
Example from a session
Every 2 minutes a timer vibrates, and the RBT glances at Mateo and records whether he is in his seat at that instant. Over a 30-minute class she checks 15 times; Mateo is seated at 12 of the checks, so the result is 80% of intervals. She records exactly what she sees at the moment of the check, even if Mateo was out of his seat for most of the preceding interval.
For BCBA candidates and supervisors
MTS has no systematic direction of error, and its accuracy depends on the interval length relative to episode duration; with short intervals it approximates the proportion of time well for long-duration behavior. A related method, PLACHECK, applies the momentary check to a group (how many people are engaged at that moment). Analysts avoid MTS for brief, high-rate, or dangerous behaviors, where missing occurrences would mislead decisions.
Often confused with partial-interval recording, whole-interval recording
MTS looks only at the instant the interval ends. Partial interval watches the whole interval and scores any occurrence; whole interval watches the whole interval and scores only if the behavior lasts throughout. If the observer is not required to watch during the interval, it is MTS.
Exam tip
"At the moment," "at that instant," or "when the timer goes off" means MTS. If an option says the observer must watch the whole interval, it is not MTS.
Can you spot momentary time sampling in a scenario?
Practice RBT A.2 with exam-style questions and instant feedback.