Which of the following best describes IRT?

The best description of Inter-Response Time (IRT) is indeed the time elapsed between two successive behaviors. IRT is a key measurement in behavioral analysis that captures the interval between one instance of a behavior and the next. This metric is particularly important in understanding the patterns of behavior and the time dynamics within behavioral sequences. By analyzing IRT, practitioners can glean insights into how quickly a behavior is repeated and make observations about the effectiveness of interventions over time.

Other options focus on different aspects of behavior but do not accurately define IRT. For instance, capturing the duration of the entire behavior relates to how long a particular behavior lasts, which is not the same as measuring the time between occurrences. Similarly, counting total occurrences of a behavior pertains to frequency rather than the time elapsed, and the rate of response during observation represents how often a behavior occurs over a specific time frame, again distinct from the concept of IRT. Understanding these differences helps clarify why the first option accurately encapsulates the essence of IRT.