Momentary time sampling (MTS) is a data collection method in ABA therapy in which therapists check whether a behavior is happening at the exact end of a set time interval. Think of it as behavior sampling — instead of recording what your child is doing every second, the therapist checks at specific moments throughout the activity.
Data collection is a core component of ABA because it helps therapists track a child’s behavior and progress over time. However, continuous observation isn’t always practical — such as in busy classrooms, during group activities, or when tracking behaviors that continue for long periods. In these instances, momentary time sampling enables therapists to collect useful behavior data without watching the child every second.
If you’re new to how ABA therapy works, this article will give you a helpful overview of how and why we track behavior through methods like momentary time sampling to help your child achieve their goals.
How Does Momentary Time Sampling Work?
Momentary time sampling in ABA follows a straightforward process: the therapist identifies a target behavior that the child is working on, chooses a session length and interval length, checks for the behavior at the end of every interval, and records data.
Setting equal time intervals
The therapist decides how long a behavior will be observed and divides that time into equal intervals. For example, during a 30-minute classroom activity, they might check the child every five minutes using a timer.
Checking the exact moment and recording data
Every time the timer goes off, the therapist looks to see whether the target behavior is happening at that exact moment. What happened earlier in the five-minute interval isn’t counted.
At each observation point, the therapist records whether the target behavior is occurring, using a plus sign (+) for occurrence and a minus sign (–) for non-occurrence.
Example: A child is working on staying engaged during a five-minute learning activity, and the therapist checks once per minute.
- Minute 1: Child is on-task (+)
- Minute 2: Child is off-task (–)
- Minute 3: Child is on-task (+)
- Minute 4: Child is on-task (+)
- Minute 5: Child is off-task (–)
At the end, the therapist divides the number of on-task observations by the total number of observations. If a child was on-task during three of five checks, for example, the data would show on-task behavior during 60% of the sampled moments. This data is plotted on a line graph so that therapists can track progress over time.
When Is Momentary Time Sampling the Right Method?
The right data collection method depends on the behavior being measured and the setting. MTS is particularly useful in two situations:
Group settings and multiple clients
During group sessions, RBTs often need to collect data while still helping other children participate and practice skills. MTS makes it easier to do so by limiting data checks to scheduled moments. For example, during center-based ABA therapy, an RBT might check at scheduled moments whether a child is engaging in repetitive vocalizations while still facilitating the group activity.
Long or ongoing behaviors like on-task work
MTS is also useful for behaviors that continue over time, such as staying on-task, participating in play, or remaining seated during an activity. During in-school ABA therapy, for example, an RBT might check every five minutes during independent work to see whether the child is working on their assignment.
Momentary Time Sampling vs. Other Discontinuous Methods
Momentary time sampling is one of three common discontinuous measurement methods, along with partial-interval and whole-interval recording. Unlike continuous data collection — when therapists observe and record behavior throughout the entire session — discontinuous data collection records behavior as it occurs at predetermined intervals.
How it compares to partial-interval recording
Partial-interval recording tracks if behavior has occurred at any point during the interval — not just at the end. For example, if a child calls out once during a five-minute interval but is quiet when it ends, PIR would track the behavior but MTS would not.
PIR is often useful for tracking behaviors that the care team wants to reduce. MTS, on the other hand, is less likely to overestimate behavior than PIR and can be useful for tracking ongoing skills a child is working to increase, such as staying on-task.
Research comparing the two methods supports using MTS for behaviors measured by duration and partial-interval recording for those measured by frequency.[1]
Pros and cons to keep in mind
No data collection method captures everything perfectly, and different methods have their own limitations.[2] BCBAs consider the pros and cons of MTS when choosing the best way to measure a child’s progress.
Pros:
- Practical: Therapists only need to check the behavior at scheduled moments, making MTS easier to use while actively supporting a child.
- Useful for ongoing behaviors: It can provide a good picture of behaviors that occur over longer periods, such as staying on-task.
- Works well in busy settings: MTS can be easier to use during classroom or group activities.
Cons:
- Can miss behavior: Anything that happens between observation points may not be captured.
- Not ideal for brief or infrequent behaviors: These can easily happen between checks.
- Interval length matters: Longer gaps between checks can make the data less representative of what happened throughout the activity.
How United Care ABA Uses Momentary Time Sampling
At United Care ABA, data helps the care team understand a child’s progress and make informed decisions about treatment.
Tracking behavior in school and community settings
United Care supports children across school and community settings, where skills can be practiced during the routines that matter in everyday life.
MTS allows RBTs to teach and support the child while still measuring progress. During a classroom lesson, for example, an RBT can help a child participate while checking at scheduled moments to see whether engagement is improving.
How our RBTs are trained on accurate data collection
United Care ABA (UCABA) RBTs are trained under BCBA guidance to collect data accurately and consistently. That includes learning how to clearly identify the behavior being measured, follow the correct observation intervals, and record what they see without relying on assumptions.
This means your child’s progress isn’t based on guesswork — the care team has clear information about what’s improving, where your child may need more support, and when treatment should be adjusted.
These skills are also part of BACB competency requirements for RBTs, which include demonstrating accurate data collection using methods such as momentary time sampling.
Ready to Learn More About How We Track Progress?
When your child is in ABA therapy, you want to know that the support they’re receiving is making a measurable difference. Momentary time sampling data collection helps UCABA’s therapists turn everyday observations into information the care team can use to see progress, recognize challenges, and make informed decisions about what comes next.
Ready to learn how ABA therapy could support your child? Explore our parent resources or contact United Care ABA to learn more about our approach.
FAQs
What are some momentary time sampling examples in ABA?
A common example is checking every 5 minutes during a 30-minute activity to see if a child is staying seated. Instead of watching the whole 30 minutes, the therapist only looks at the 5, 10, 15, 20, 25, and 30-minute marks and records a yes or no each time.
What is the difference between momentary time sampling and partial interval recording?
Momentary time sampling only checks if a behavior is happening at the exact end of an interval, while partial interval recording marks “yes” if the behavior happens at any point during the interval. Partial interval tends to overestimate behavior, while momentary time sampling gives a more balanced snapshot.
How do you collect momentary time sampling data?
You divide the observation period into equal intervals, set a timer or alert for the end of each one, and check whether the target behavior is occurring at that exact moment. Each check is marked as a yes or no, and the results are turned into a percentage.
When is momentary time sampling the best method to use?
It works well for long or ongoing behaviors like staying on-task, and in group settings or busy environments where a therapist can’t watch one behavior every second. It’s especially useful when supervising more than one child at a time.
Can momentary time sampling miss important behavior?
Yes. Because it only checks specific moments, it can miss behavior that happens between checks, which may slightly under- or overestimate how often something actually occurs. Shorter intervals generally reduce this gap.
