Discrete trial training: What it is and how it works.

Discrete trial training is a way of teaching that breaks a skill into small, clear pieces and practices each piece in short, repeated rounds called trials. Each trial has a definite beginning and end: the adult gives an instruction, your child responds, and the adult responds right away, usually with something your child enjoys if the answer was right. The 2020 national review of autism practices by the National Clearinghouse on Autism Evidence and Practice (NCAEP) defines DTT as instruction with massed or repeated trials, each made up of the teacher's instruction, the child's response, a carefully planned consequence, and a pause before the next instruction.

You will also hear it called discrete trial teaching or discrete trial instruction, which mean the same thing. "Discrete" means separate: each trial stands on its own, so the therapist can count how many your child got right and how much help each one took.

People sometimes use DTT and ABA as if they were the same thing, but DTT is one teaching method within ABA. Our guide to what is ABA therapy explains the bigger picture, and most programs today mix DTT with other ABA therapy techniques, choosing the method that fits each goal.

Every trial follows the same pattern, and the technical terms for each part show up in treatment plans and data sheets.

A trial starts with the instruction, which behavior analysts call the discriminative stimulus, or SD: a short, consistent cue such as "Touch dog." While a skill is new, the therapist may add a prompt, like pointing or gently guiding a hand. Your child's response can be correct, incorrect, or no response at all, and the consequence follows right away, usually reinforcement such as praise or a turn with a toy after a correct answer. The inter-trial interval is the short pause that closes the trial.

If your child touches the car instead, a good therapist gives a brief, neutral response and runs the trial again with more help, so your child ends on a success. Shuffling the pictures between trials keeps your child from learning that the dog is always on the left.

Prompts are the support that helps your child respond correctly. Common types, from the most help to the least, include full physical guidance, partial physical guidance, modeling the answer, gestures such as pointing, and verbal hints. NCAEP lists prompting as its own evidence-based practice and defines it as verbal, gestural, or physical assistance that helps a learner acquire or use a skill.

The goal is always to remove that help, a process called prompt fading. A therapist might start by guiding your child's hand to the dog, then only point, then give no help at all. Some programs fade from most help to least, others start with the least help and add more only when needed, and many use a short wait before prompting, called time delay, so your child can answer alone first. When prompts aren't faded on a plan, children can learn to wait for help instead of answering. Clinicians call this prompt dependence, and a 2015 paper by Laura Schreibman and other leading autism researchers lists it among the problems linked to highly structured teaching in the 1980s.

Errorless learning is an approach that tries to keep mistakes from happening in the first place. For a brand-new skill, the therapist prompts immediately, so your child practices only the correct response, and then fades the prompt gradually. The reasoning is that repeated errors frustrate children and can harden into habits, though errorless teaching still depends on careful fading so your child doesn't come to rely on the prompt.

In massed trials, the therapist presents the same instruction several times in a row. Massed practice is common when a skill is brand new, and the AFIRM training module on DTT, from the university team behind the NCAEP review, describes teaching new steps this way. It builds a first correct response quickly, although a child can get a massed trial right by repeating whatever worked last time without understanding the instruction.

Mixed or interspersed trials, sometimes called random rotation, place the new target among skills your child already knows. "Touch dog" might come after "Clap your hands" and before "Touch cup," so your child has to listen to each instruction, which is the real test of learning. The easy, mastered skills also keep your child succeeding often. Many programs teach a target in massed trials first, then move it into mixed trials before calling it mastered.

DTT is strongest for new skills that have a clear right answer. Tristram Smith, a researcher who studied the method for decades, wrote in a 2001 review that DTT is especially useful for teaching new forms of behavior, like speech sounds or motor movements a child couldn't make before, and new discriminations, like responding correctly to different requests. In practice that often means imitation, matching, labeling objects, and following one-step directions. The studies behind the NCAEP listing cover outcomes in communication, social, play, academic, adaptive, and school readiness skills, with learners from infancy through young adulthood.

It is weaker for skills that depend on your child starting an interaction. Smith's review cautions that DTT must be combined with other interventions so children learn to initiate the use of their skills and use them across settings. Conversation, pretend play, joining a game with other children, and asking for help when no adult has given a cue are hard to teach through adult-led trials alone.

The biggest practical limit is generalization, meaning a skill showing up outside the place it was taught. A child who touches the dog picture at the therapy table may not point to a real dog at the park. Schreibman and colleagues list poor generalization, a lack of spontaneity, and escape-motivated problem behavior among the problems researchers linked to rigid table teaching. Good programs plan for generalization from the first day, usually by:

• Teaching with many examples, such as different dog photos, toy dogs, and real dogs.
• Rotating who runs the trials and varying the wording, so "Where's the dog?" works as well as "Touch dog."
• Practicing the skill during play, snack, and outings, often through natural environment teaching.
• Coaching you to use the skill at home, and checking that it holds up weeks after mastery.

Naturalistic approaches teach many of the same skills inside play and daily routines, following your child's lead. If your child reaches for the bubbles, the therapist might wait for a word or sign before blowing them, and the bubbles themselves are the reward. Schreibman and colleagues grouped several of these methods, including pivotal response treatment, under the name naturalistic developmental behavioral interventions (NDBIs), which share control between child and adult and rely on natural consequences.

Research comparing the two is limited and often small, but it leans one way for language. Dennis Delprato's 2001 review of ten controlled studies found that in all eight measuring language targets, looser, child-led training was more effective than discrete-trial training. A 2015 randomized trial with 30 autistic children aged 6 to 11 in Iran found significantly less disruptive behavior during pivotal response sessions than during adult-directed, drill-style ABA, though it lasted only three months. Schreibman and colleagues noted that no head-to-head randomized trial of NDBI versus DTT had been published when they wrote, and they still called massed-trial teaching the approach of choice for certain skills at certain times.

For most children the practical answer is a blend, with DTT for specific targets and naturalistic teaching to make those skills spontaneous. Our guide to naturalistic ABA covers those methods in depth.

For a three- or four-year-old, DTT at a good clinic usually happens in short sets of a few minutes, at a small table or on the floor, woven between stretches of play. Before a set, the therapist often lets your child pick what they'd like to earn, because preferences change from hour to hour. Reinforcers come from your child's own interests, whether that's spinning toys, a song, or a tickle game, and good sets mix easy tasks with new ones and end on a success.

Assent is your child's ongoing willingness to take part, shown through words or behavior such as coming to the table and reaching for the materials. In assent-based practice, the therapist watches for signs that willingness has gone, like turning away, crying, or trying to leave, and responds by pausing, offering a break or a choice, or switching activities. Your child should have a way to ask for a break, whether with words, a sign, a picture card, or a device, and that request should be honored.

Setting changes how DTT feels as well, since in-home ABA therapy can fold short sets of trials into your routines at the kitchen table, while a center may have a work area next to a play space. Wherever it happens, you should be able to watch, and DTT should never look like any of the following, and each one is a reason to raise concerns with the supervising BCBA right away:

• Physically forcing your child to stay at the table, or holding them in place to finish trials.
• Running trials while your child cries or tries to leave, with the message that they can stop only after they comply.
• Withholding things your child needs, like food, water, or a comfort item, to use as rewards.
• Long stretches of drills with no play or breaks, and no change when the data shows your child isn't progressing.
• Goals aimed at making your child look less autistic, such as stopping harmless stimming or demanding eye contact for its own sake.
• Harsh corrections, raised voices, or any form of punishment presented as part of teaching.

Some autistic adults describe lasting harm from rigid, compliance-focused programs they went through as children. Those accounts are a large part of why parents search is ABA therapy harmful, and our guide covers that debate and how the field has responded.

DTT grew out of work by O. Ivar Lovaas and his colleagues at UCLA in the 1960s and 1970s, which became the UCLA Young Autism Project. Those early programs were intensive, adult-directed, and mostly table-based, and they sometimes used physical punishment, which ethical practice rejects today. In 1987, Lovaas published a study reporting that some young children who received about 40 hours a week of one-to-one behavioral treatment reached normal educational and intellectual functioning. The study became a model for early intensive programs, and its design and claims have been debated ever since.

By the mid-to-late 1980s, researchers had documented the limits of rigid table teaching, and that work led to naturalistic methods and to more flexible DTT. Better programs today use reinforcers your child picks, plan prompt fading from the start, and pay attention to assent, with DTT as one part of the program instead of the whole thing.

NCAEP's 2020 review, which covered studies published from 1990 to 2017, lists discrete trial training as one of 28 evidence-based practices for autistic children, youth, and young adults. Almost all of the studies behind that listing are single-case designs, which follow a few children closely and can show that a method changed a specific skill, but can't show on their own how well it works for children in general. Smith's 2001 review adds that there is controversy over how many hours of DTT young children should get, and that therapists need specialized training to run it well. Research also hasn't settled whether DTT or naturalistic methods lead to better long-term outcomes, and studies rarely ask children how sessions felt.

The BCBA designs your child's program and decides when to use DTT, and a registered behavior technician usually runs the trials day to day. If you're not sure how those roles divide the work, our explainer on what is a BCBA covers both credentials. These questions will tell you a lot about how DTT is used with your child:

• Which of my child's goals will you teach with DTT, and why is DTT the right method for each one?
• How much of a typical session is DTT, and how much is play-based or naturalistic teaching?
• How do you choose reinforcers, and how often do you check what my child wants to earn?
• What is the prompt fading plan for each target?
• How do you plan for my child to use new skills at home and at school?
• What happens when my child cries, refuses, or asks for a break?
• Can I watch a DTT session and see the data on each target?

Clear, specific answers are a good sign, while vague answers or answers that treat compliance as the main goal are worth pressing on. Our checklist on how to choose an ABA provider has more questions for clinic tours, and our directory is the place to start if you're searching for ABA therapy near me.