Intertrial interval
The brief pause between the consequence of one discrete trial and the presentation of the next trial's instruction, typically a few seconds.
In discrete trial teaching, each trial ends with a consequence, and the intertrial interval (ITI) is the short pause before the next SD. The RBT uses the ITI to record data, reset or rearrange materials, and get ready for the next instruction. The pause also makes each trial distinct, so the learner can tell one opportunity from the next.
The ITI is usually short, a few seconds, to keep instruction moving and to give the learner many learning opportunities. Short, consistent ITIs keep the learner engaged and can reduce problem behavior that occurs during long waits. Very long pauses can let attention drift and give time for other behavior to occur.
The length of the ITI is set by the supervisor, and plans may call for a longer pause after a reinforcer such as a brief play break. An RBT who finds they need a long time to record data between trials should ask the supervisor about simpler data sheets rather than letting the pace slow down.
Example and non-example
| Example | After the client touches the correct color and gets praise, the RBT marks a plus on the data sheet, shuffles the cards, and three seconds later says the next instruction. |
|---|---|
| Non-example | The time between the RBT saying "Touch red" and the client's response is the response latency within the trial, not the intertrial interval. |
Don't confuse it with
| Latency | Latency is the time from an SD to the start of the response; the intertrial interval is the time between one trial's consequence and the next trial's SD. |
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| Interresponse time | Interresponse time is the time between two responses; the intertrial interval is the pause between trials that the teaching procedure sets. |
Test yourself
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Question 1Which sequence shows the core parts of a discrete trial in the correct order?
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A: Instruction, learner response, consequence, intertrial interval. A discrete trial begins with a brief instruction (the discriminative stimulus), followed by the learner's response and then a consequence, with a short intertrial interval before the next trial. A prompt, when the plan calls for one, is given with or right after the instruction.
- B: The consequence follows the response; it cannot come before the instruction that starts the trial.
- C: A discrete trial starts with the instructor's instruction (the SD), and the response comes after it.
- D: The intertrial interval is the pause after the consequence, between one trial and the next.
Task C.3 · 40-hour curriculum section E
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Question 2After giving a client a reinforcer for a correct response, an RBT writes the data, waits about three seconds, and then gives the next instruction. What is this brief pause called?
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D: Intertrial interval. The intertrial interval is the short pause between the end of one trial (the consequence) and the instruction that starts the next. RBTs often use it to record data and reset materials.
- A: Latency is the time from an instruction to the start of the client's response, not the pause between trials.
- B: A prompt delay is the time between the instruction and the prompt within a trial.
- C: A limited hold is a time window in which a response must occur to be reinforced, not the gap between trials.
Task C.3 · 40-hour curriculum section E
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Question 3A plan calls for trial-by-trial data on each discrete-trial target. When should the RBT record the data?
Show answer
C: Right after each trial, during the intertrial interval. Trial-by-trial data are recorded for every trial as it happens, usually during the intertrial interval, so the record is accurate.
- A: Recording from memory later makes errors likely and makes the data unreliable.
- B: Trial-by-trial data include every trial, correct and incorrect.
- D: Recording only some trials is not trial-by-trial data.
Task C.3 · 40-hour curriculum section E
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On the RBT exam
This term belongs to task C.3 Discrete-trial teaching in content area C, Behavior Acquisition, which is 19 of the 75 scored questions.