If you have spent any time reading about ABA therapy, you have almost certainly encountered two terms that seem to come up constantly: Verbal Behavior (VB) and Discrete Trial Training (DTT). Parents want to know which approach their child's program uses. New RBTs are taught both and often confused about how they relate. Even among practitioners, the terms are sometimes used imprecisely.
This article explains what each approach is, where it comes from, how it is used in clinical practice, and — crucially — why the question of "which one" misses the point of how good ABA programs actually work.
What is Discrete Trial Training?
Discrete Trial Training is a structured teaching format, not a curriculum or philosophy. In a DTT trial, the therapist presents a specific antecedent stimulus (a instruction or question), the learner responds, and the therapist delivers a consequence (reinforcement for correct responses, a neutral error correction for incorrect ones). The term "discrete" refers to the fact that each trial has a clear beginning, middle, and end, separated from the next trial by a brief inter-trial interval.
A typical DTT session involves multiple trials of the same target presented in a massed or distributed format. For example, a therapist teaching a child to identify colors might present "Touch red" 20 times across a session, interspersed with other known targets to maintain motivation.
DTT originated in the work of Dr. Ivar Lovaas at UCLA in the 1960s and 1970s. Lovaas demonstrated that structured behavioral teaching could produce significant language and social gains in children with autism who had previously been considered untreatable. His early research used high-intensity, adult-directed teaching formats — the "table-based drill" image that many parents associate with ABA.
What is the Verbal Behavior approach?
The Verbal Behavior approach is grounded in B.F. Skinner's 1957 analysis of language as learned behavior. Skinner argued that words are not simply labels for objects — they are behaviors shaped and maintained by their consequences. He identified distinct categories of verbal behavior based on their functional relationships: mands (requests driven by a state of deprivation — "cookie" when the child wants a cookie), tacts (labels driven by direct contact with a stimulus — "cookie" when a cookie is present), echoics (repetition of heard speech), intraverbals (responses to verbal stimuli — answering "what do you eat?" with "pizza"), and textuals (reading).
The Verbal Behavior approach — particularly as developed by Dr. Mark Sundberg and Dr. James Partington in the 1990s and 2000s — applies Skinner's framework to ABA programming for children with language delays and autism. It emphasizes teaching communication functionally rather than through rote labeling, prioritizes the mand repertoire as the foundation of language, and integrates teaching across natural environments rather than restricting it to structured table time.
A VB-based program focuses heavily on motivation: teaching occurs when the child is in a state of deprivation for a preferred item (they want the cookie and will work to get it), making the learning highly functional and generalized from the start.
The key differences
The most important distinction is this: DTT is a teaching format; Verbal Behavior is a theoretical framework and curriculum approach. A VB-based program can and does use DTT as a teaching format for certain skill areas. The two are not mutually exclusive — they operate at different levels of abstraction.
In terms of how they look in practice: DTT typically occurs at a table or in a structured setting with a consistent format across trials. VB-informed teaching often looks more naturalistic — teaching happens during play, snack time, and transitions, embedded in activities that are already reinforcing. VB programs tend to emphasize the mand early and heavily, because the ability to request is the most functionally powerful language skill a child can develop.
DTT is particularly effective for building new discriminations, establishing stimulus control quickly, and teaching skills that require many repetitions to acquire (color identification, number concepts, category matching). Natural Environment Teaching (NET) — the delivery format most associated with VB — is more effective for generalization, spontaneous language, and social communication.
Assessment tools used in each approach
Programs with a strong VB orientation commonly use the VB-MAPP (Verbal Behavior Milestones Assessment and Placement Program, developed by Sundberg) to assess current language levels and guide goal selection. The VB-MAPP evaluates mand, tact, listener responding, visual perceptual skills, intraverbal, vocal imitation, and social skills across three developmental levels.
Programs with a broader behavioral skills focus may use the ABLLS-R (Assessment of Basic Language and Learning Skills, Revised), the AFLS (Assessment of Functional Living Skills), or the Vineland Adaptive Behavior Scales alongside or instead of the VB-MAPP. Each tool has different strengths depending on the child's profile and the goals of assessment.
When each approach is most appropriate
For a child who is minimally verbal or pre-verbal, a VB-based program that prioritizes mand training in highly motivating contexts is typically the appropriate starting point. Getting the child to communicate — to reliably request the things they want and need — is the functional foundation everything else is built on.
For a child who has an established communication foundation but needs to build specific academic or adaptive skills, structured DTT may be used more heavily alongside NET. DTT is efficient for building new concepts that require repeated exposure to establish stimulus control.
For most children, the best program uses both: structured DTT blocks for specific acquisition targets, integrated with natural environment teaching that creates generalization opportunities throughout the session. A BCBA who insists on exclusively one approach — regardless of the child's profile — is a clinical red flag.
What to ask your child's BCBA
Rather than asking "do you use VB or DTT?", ask these more revealing questions: How do you decide which teaching format to use for a given skill? How do you measure generalization — can my child use the skills they learn with different people and in different settings? What does the ratio of structured teaching to natural environment teaching look like in a typical session? How do you fade prompts, and what is your error correction procedure?
The answers reveal whether the BCBA is making evidence-based, individualized clinical decisions — or applying a rigid template regardless of the child's needs and response to teaching.
The evolution beyond the debate
In current ABA practice, the "VB versus DTT" framing is increasingly understood as a false dichotomy. The field has moved toward an evidence-based pluralism: BCBAs are trained to select teaching procedures based on the target skill, the learner's profile, and the data. What matters is whether the child is making measurable progress, generalizing skills to natural contexts, and developing meaningful independence.
The most important thing parents can look for is a BCBA who can articulate why each element of the program is designed the way it is — who uses data to drive decisions, adjusts strategies when a child is not making progress, and involves the family in understanding what is being taught and why.