Discrete trial training (DTT) is a process whereby an activity is divided into smaller distinct sub-tasks and each of these is repeated continuously until a person is proficient. The trainer rewards successful completion and uses errorless correction procedures if there is unsuccessful completion by the subject to condition them into mastering the process. When proficiency is gained in each sub-task, they are re-combined into the whole activity: in this way proficiency at complex activities can be taught.: 93 DTT is carried out in a one-on-one therapist to student ratio at the table. Intervention can start when a child is as young as two years old and can last from two to six years. Progression through goals of the program are determined individually and are not determined by which year the client has been in the program. The first year seeks to reduce self-stimulating ("stimming") behavior, teach listener responding, eye contact, and fine and gross motor imitation, as well as to establish playing with toys in their intended manner, and integrate the family into the treatment protocol. The second year teaches early expressive language and abstract linguistic skills. The third year strives to include the individual's community in the treatment to optimize "mainstreaming" by focusing on peer interaction, basic socializing skills, emotional expression and variation, in addition to observational learning and pre-academic skills, such as reading, writing, and arithmetic. Rarely is the technique implemented for the first time with adults.DTT is typically performed five to seven days a week with each session lasting from five to eight hours, totaling an average of 30–40 hours per week. Sessions are divided into trials with intermittent breaks, and the therapist is positioned directly across the table from the student receiving treatment. Each trial is composed of the therapist giving an instruction (i.e., "Look at me", "Do this", "Point to", etc.), in reference to an object, color, simple imitative gesture, etc., which is followed by a prompt (verbal, gestural, physical, etc.). The concept is centered on shaping the child to respond correctly to the instructions throughout the trials. Should the child fail to respond to an instruction, the therapist uses either a "partial prompt" (a simple nudge or touch on the hand or arm) or a "full prompt" to facilitate the child to successfully complete the task. Correct responses are reinforced with a reward, and the prompts are discontinued as the child begins to master each skill.The intervention is often used in conjunction with the Picture Exchange Communication System (PECS) as it primes the child for an easy transition between treatment types. The PECS program serves as another common intervention technique used to conform individuals with autism. As many as 25% of autistic individuals have no functional speech. The program teaches spontaneous social communication through symbols or pictures by relying on ABA techniques.  PECS operates on a similar premise to DTT in that it uses systematic chaining to teach the individual to pair the concept of expressive speech with an object.  It is structured in a similar fashion to DTT, in that each session begins with a preferred reinforcer survey to ascertain what would most motivate the child and effectively facilitate learning.