So much of our life is measured. When I drive to work, my speed is measured by my car. When I have a doctor’s appointment, they check my weight, blood pressure, and heart rate. My smart watch measures my daily steps and notifies me if I’ve been sitting for too long. While in school, my performance was measured in percentages when I took exams or wrote papers. All of these measurements, along with many others not mentioned, are used to help us understand our behaviors and make changes where we need to.
This same view of measurement applies in applied behavior analysis (ABA) therapy, where measurements of behavior are crucial to track progress and make decisions regarding treatment. Duration and frequency are certainly the most common types of measurement when it comes to ABA. A lesser-known measurement is interresponse time, or IRT. IRT helps to better analyze and understand the pacing of a person’s behavior.
IRT refers to the time that passes between two consecutive responses. That is, how much time passes between each instance of a particular behavior occurring. It helps to better look at how quickly or slowly a person engages in a behavior. IRT allows ABA professionals to look at the efficiency of a behavior and make changes specific to the individual’s needs and abilities. This article will look a little deeper at interresponse time as a measurement, why it matters, and how the information learned from IRT can influence behavior chance and skill acquisition.
The Science Behind IRT in ABA Therapy
Behavioral Principles of IRT
As mentioned above, IRT is a concept used to help determine how quickly someone responds to something after their previous response. It’s the measurement of the time between behaviors.
For example, if a child is instructed to put away their toys, IRT would measure the amount of time between each instance of them putting a toy away. If the time between the behaviors is short, it can be assumed that they are familiar with the task, and it is well-established in their repertoire. If the time between behaviors is longer, it may mean that they are not as familiar with the task. What occurs before and after the behavior, such as with prompts and reinforcement, also plays a heavy role in how quickly someone engages in a behavior.
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Measuring IRT
Measuring IRT is a simple measure to take once it is learned, but it can be a bit time-consuming. Let’s say we are measuring tantrums using IRT. That would mean that the time between tantrums would be measured. If a child starts to engage in a tantrum, the time recording would stop. Once the tantrum is over, the timer would start recording and would continue until the behavior occurs again. The times between the tantrums would be recorded to see how much time passes between each instance of behavior.
For behaviors that occur more frequently, measuring IRT can be a bit more effortful in that the person recording has to be extremely attentive to ensure that the data is accurate. For behaviors that occur a bit less frequently, such as tantrums that occur a few times per hour, the measurement may be a bit easier to manage. Regardless of the time length, the principles stay the same. When a behavior ends, time is counted until that behavior happens again.
Applications of IRT in ABA Therapy
Reducing Problem Behaviors
Looking at IRT can help to reduce problem behaviors, such as tantrums, by increasing the time between occurrences. Let’s say that a child engages in a tantrum every 15 minutes. Knowing this information, ABA professionals can work to extend the IRT between tantrums so that they occur once every few hours. The idea here is that if a child can go longer between tantrums, they are learning to better manage frustration or triggers more effectively.
The goal time for IRT between tantrums may gradually increase, with positive reinforcement and praise being used as the IRT grows. After a child starts having tantrums around every 20 minutes, the new goal may become 25 minutes, and so on.
Promoting Skill Fluency
IRT can also be used to improve the fluency of new skills. In an academic setting, for example, IRT may be measured between each time a math problem is completed. For children who have a low IRT between each addition problem solved, it could be assumed that the child knows addition well and is skilled in math. For children who have a larger IRT between math problems, they are spending more time solving math problems and may not be as confident in mathematics. In promoting fluency, a shorter IRT may be more desirable.
In social interactions, a shorter IRT may also be ideal. For example, if IRT is being measured between each instance of a child interacting with other children during playtime, a shorter IRT assumes that the child is engaging with other kids more frequently. This can be an especially important measure for children on the spectrum, who often struggle with social interactions with peers. Focusing on decreasing IRT between interactions can help to develop stronger social skills, improve relationships with peers, and build confidence.
Monitoring Treatment Progress
IRT is important for evaluating the effectiveness of interventions in ABA therapy. IRT can help ABA professionals monitor changes in behavior over time to determine if a particular intervention is working. For example, while tracking tantrums, they can monitor IRT to see if IRT is growing larger as the intervention continues. If IRT is not changing or is decreasing after some time, changes to the intervention can be made so that more effective strategies can be used.
Different reinforcement schedules, modifying prompts, or teaching related coping skills may be considered if tantrum IRT remains the same or decreases. Continuing to review IRT data can help to make data-driven decisions to ensure that treatment is effective and tailored exactly to the child’s needs.
Strategies for Addressing IRT in Interventions
Shaping Desired IRTs
In ABA therapy, reinforcement schedules play one of the biggest roles when it comes to shaping IRT (and all other data measures, for that matter). Managing how often reinforcement is provided helps ABA professionals to guide a child toward achieving goals. For example, if the goal is to reduce IRT, therapists may use a more dense reinforcement schedule, meaning that reinforcement is much heavier and more frequent after each correct response. This encourages the child to respond more frequently, reducing overall IRT.
On the other hand, if the goal is to increase IRT, therapists may use a lighter reinforcement schedule, only using reinforcement after a longer interval of time has passed. This method of reinforcement can help a child to tolerate longer periods between behaviors.
To systematically increase or decrease IRT, ABA professionals choose smaller, obtainable goals. Changes don’t happen overnight. The process of changing behavior is gradual, and so plans typically involve changing the goal IRT a few minutes or a few seconds at a time. The key here is to adjust reinforcement and expectations based on the child’s progress and the child’s ability to adapt to the changes without frustrating or overwhelming them.
Prompting and Fading
In ABA, prompting is used to help teach and shape behaviors. Using prompts to shape IRT is no different. For example, if a child is learning how to use an AAC device to request items, hand-under-hand or model prompting may be used to teach them to use it more frequently. Once they can use their device independently, a visual prompt (such as pointing to the device or a picture of it) or a verbal prompt (telling the child to use their device) may be used to teach them to use it more frequently.
With prompting and immediate reinforcement after each successful request, the IRT should begin to decrease. Once changes are made, prompting and reinforcement schedules change so that the child can use their AAC to communicate frequently and without the need for prompts.
Environmental Modifications
Environmental modifications can also help to change IRT. As a matter of fact, environmental factors can play an incredibly significant role in IRT. For example, for a child who has tantrums, it may be noticed that in certain places or around certain stimuli, tantrums occur much more frequently. In these instances, making environmental modifications can make the most significant and immediate changes.
I have worked with many children who are sensitive to sounds and engage in high rates of problem behaviors when it is too loud in a room. Having them engage in more quiet rooms and having them play around quieter children dropped problem behaviors significantly. For some children, giving them access to noise-cancelling headphones in louder areas had the same effect. Other modifications, such as introducing visual prompts or timers, can help to reduce or increase IRT depending on the behavior goal.
Challenges in Measuring and Applying IRT
Accuracy in Data Collection
Accuracy is important when it comes to measuring IRT. Inaccurate measurements are useless measurements. If the measurements are wrong, they aren’t reliable and cannot be used to make meaningful changes. For accurate IRT data, the people recording measurements need to be attentive and properly trained. Having a solid, understandable definition of a behavior is a great start. This allows for recorders to know the exact moment a behavior begins and when it ends.
This sounds simple at face value, but take tantrums for example — does a tantrum start when the child starts to whine? Does a tantrum start when they start crying, or when they begin screaming? Is it when they first flop onto the floor, or is that not a necessary component? Having precise definitions of what a behavior looks like can help to make sure that IRT data is consistent.
Real-world settings may not always be ideal when collecting IRT data. In busy or unpredictable environments, it can be difficult for measurement takers to track exact timings. In addition, if one person is in charge of collecting data for multiple people, this can also cause accuracy concerns. Measurement technology can also come with its own set of barriers. For example, having a manual timer or recording device may not be practical, especially if the child engages in behaviors that make it difficult to measure consistently. For each case in which IRT is used, the professionals involved should always consider measurement concerns to make sure that IRT data collection methods are practical.
Balancing IRT Goals with Other Behavioral Metrics
There are many, many other types of measurement in ABA. IRT may interact with other behavioral measures like duration (i.e., the total amount of time that a behavior lasts), latency (the time between a stimulus and a response), or accuracy (percentage of correct responses). Keeping an eye on only IRT for answering math questions, for example, may not be reflective of the child’s math abilities. They may lower IRT for completing math problems, but they may also be getting the math problems wrong.
Another example is tantrums. For tantrums, it is also important to take note of duration. Even if the IRT increases between tantrums, making sure that the duration of tantrums does not increase is just as important. Balancing IRT goals with other measures is ideal for the best possible results.
My Perspective as a BCBA
Personally, I have never collected or used IRT data with any of my ABA clients. It is a great measurement tool to know, and I am, of course, open to using it if a case warrants it, but I have had success using other forms of data. Frequency and duration data for problem behaviors are usually easier to measure across the board, and they are much easier to teach others how to record. For some cases, though, IRT may be a great option, so it is a good measurement to know.
For parents of children who participate in ABA sessions, I would tell them to talk more to their child’s behavior analyst about the measurements they use to measure behaviors. BCBAs are trained on when to use certain measurements, so they are often the best source of information if parents are curious about why one particular method may have been chosen over another.
Common Myths and Misconceptions
Myth: IRT Is Only Relevant for Problem Behaviors
Not true! IRT can be relevant for all types of behaviors, not just ones that we want to reduce. Areas such as academic skills, social interactions, and self-care routines can all be tracked and improved using IRT measurements. IRT data is often mentioned when discussing the measurement of problem behaviors, but that certainly does not mean that it is only for problem behaviors.
Myth: Shorter IRT Is Always Better
Also not true! It might seem like shorter IRTs are always ideal, but this isn’t true in all situations. For example, for children who engage in tantrums, having a longer IRT is better. In addition, having a shorter IRT but inaccurate responses (such as with the answering math problems example above) is not necessarily better than having accurate responses with a slightly longer IRT. For certain skills, taking more time between responses may result in more thoughtful and accurate behaviors.
Conclusion
IRT may not be used as frequently as other methods, but it is certainly an important one for ABA professionals to consider. Measuring IRT data can help individuals develop more effective behaviors and improve their overall functioning. It can be used to make data-driven decisions in treatment and is an overall powerful tool in behavior analysis when used correctly.
