ABA glossary
Interresponse time
Also called IRT
Definition
The time between two successive responses of the same behavior, usually measured from the end of one response to the start of the next.
In plain words
IRT shows the spacing between responses. Shorter IRTs mean responses are coming faster; longer IRTs mean they are spread out. It is useful when the pace of a behavior is the concern, such as eating too fast, asking the same question over and over, or rushing through work. IRT is closely related to rate: as IRTs get shorter, the rate rises.
Example from a session
During lunch, the RBT times how long Darius waits between bites. He finishes one bite and takes the next 3 seconds later, an IRT of 3 seconds. His plan aims to lengthen IRT to at least 10 seconds by teaching him to put his fork down between bites, and the RBT records the IRT for each bite as written.
For BCBA candidates and supervisors
Most applied texts measure IRT from the end of one response to the onset of the next, while some laboratory and research reports time it from onset to onset; analysts read each study's definition before comparing values. IRT is the measure behind spaced-responding DRL, a form of differential reinforcement of low rates that reinforces a response only if a minimum IRT has passed since the last one. Analysts use IRT data to decide whether a behavior should be reduced, as with excessive questioning, or only spaced out.
Often confused with latency, rate
IRT runs between two responses of the same behavior; latency runs from a cue to a response. IRT and rate are related but different: rate counts responses per unit of time, while IRT measures the gap between each pair. A stem with no instruction or cue at the start, only a previous response, is describing IRT.
Exam tip
Ask what started the clock. The end of the last response means IRT; an instruction means latency. If the plan is to slow behavior down without eliminating it, expect lengthening IRT or spaced-responding DRL in the answer.
Can you spot interresponse time in a scenario?
Practice RBT A.1 with exam-style questions and instant feedback.