One of the instructional methodologies frequently used in ABA-based programs is Discrete Trial Training (DTT). Discrete trial training and ABA are not synonymous. While DTT is based upon principles of learning theory and has been demonstrated to be an effective intervention methodology, it represents only one of dozens of teaching strategies within the field of ABA. For example, other methods of teaching used within ABA-based programs include PECS (Picture Exchange Communication System), photo activity schedules, chaining, shaping, graduated guidance, and functional communication training. ABA also relies heavily upon incidental teaching procedures, once children have a core set of skills necessary to learn incidentally. These include attending and imitation.

Discrete Trial Training methodology has been likened to controlling the river of information and interaction which typically confronts the child with autism such that it is presented one drop at a time (Koegel, Russo, Rincover & Schreibman, 1982). This control manages learning opportunities so that skills are more easily mastered by the child. Learning occurs in small steps. Simple skills must be mastered before new learning opportunities are presented, in which the child then builds upon the mastered skill toward a more complex one. Learning opportunities are presented in a "training trial" format.

Each training trial, regardless of the skill objective, consists of four major components:

Newsom and Rincover (1989) explain discrete trial training can be used to teach basic skills such as attending, as well as very complex verbal and social behaviors necessary to function independently.

Treatment begins with two primary goals: teaching "learning readiness" skills such as sitting in a chair and attending, and decreasing behaviors that interfere with learning, such as noncompliance, tantrums and aggression. In addition, the basic rules of social interaction are established. Children are taught how to learn from the environment through the introduction of clear stimulus-response-reward cycles.

Once the child has learned to sit quietly and attend, more complex skills such as social behaviors and communication can be taught. Social skills training begins with eye contact, and moves toward imitation, observational learning, expressive affection and social play. Communication skills generally begin with receptive object labels, progress to expressive verbal and/or augmentative expressive language, then seek spontaneous communication. As these tasks are mastered, the child is taught to make expressive demands. The goal is that the child will learn that functional language results in something the child wants. Generalization training then moves the drills into more naturalistic environments and incidental teaching (McGee, Krantz & McClannahan, 1985). Children with autism typically do not learn from their environment spontaneously, and therefore need to be taught virtually everything they are expected to learn (Green, 1995). Therefore, as part of a broader applied behavior analysis intervention, discrete trials target numerous goals and objectives. Consequently an effective ABA intervention requires numerous hours of child:therapist sessions per week. According to Green (1995), "For young children with autism, the treatment of choice is intensive application of the methods of applied behavior analysis. "Intensive" means one-to-one treatment in which carefully planned learning opportunities are provided and reinforced at a high rate by trained therapists and teachers for at least 30 (preferably 40) hours a week, 7 days a week, for at least two years. Young autistic children who received less intensive treatment made some modest gains, but normal or near-normal functioning was achieved reliably only when treatment was provided for 30 - 40 hours a week, on average, for at least two years (eg Anderson, et al, 1987; Birnbrauer & Leach, 1993; Fenske, et al, 1987; Lovaas, 1987; Maurice, 1993; McEachin, Smith & Lovaas, 1993; Perry, Cohen & DeCarlo, 1995; Smith, 1993)."