Minimally verbal children between 2.0 and 3.9 years with autism spectrum disorder (ASD) and who do not emit vocalizations, will be randomly assigned to the treatment group and will begin the stimulus-stimulus pairing (SSP) procedure. Subjects will be recorded by a vocal recorder at home by the parent/guardian at home or in the community setting.

Minimally verbal children between 2.0 and 3.9 years with autism spectrum disorder (ASD) and who do not emit vocalizations will be randomly assigned to the Waitlist Control group. During the waitlist control subject's assigned session block of six weeks, s/he will not receive any treatment. The subjects will receive the stimulus-stimulus pairing procedure (delayed procedure) after the completion of the assigned 6-week block as a waitlist control participant. Subjects will be recorded by a vocal recorder at home by the parent/guardian at home or in the community setting.

The participants will attend clinic-based treatment sessions for one hour per day, five days per week, for 6-weeks.The stimulus-stimulus pairing procedure will consist of sounds and words being systematically paired with delivery of a preferred item.

The therapist will pair echoic sounds and words with preferred items. A target vocalization is any vocal response that matches the paired sound or word. An approximation is any sound that is a component of the targeted word. A successful vocalization is when the participant emits the target or approximation of a targeted sound or word. Change is defined as the difference in the number of vocalizations at week 1 and week 6.

Vocalization data will be collected in the home via the vocal recorder device. Target vocalization is when the participant emits the target sound or word. An approximation is any sound that is a component of the targeted word. Change is defined as the difference in the number of vocalizations at week 1 and week 6.

A parent-rated checklist will assess their child's vocal language and parents will rate improvement as a yes or no question on the checklist at week 1 and week 6.

The number of times stimulus-stimulus pairing (SSP) is reliably delivered by the therapist to the participant during the treatment period of 6 weeks will be assessed. Reliable delivery consists of the therapist pairing sounds and words with preferred items in accordance to the protocol.

The level of compliance and willingness of the parents/guardian to bring the subjects to the treatment sessions will be assessed. Acceptability is when the parent/guardian brings the subject to the clinic for the treatment sessions for one hour a day, five days per week, for 6 weeks.

The level of adherence of the parent/guardian of the participants in returning the recording device to allow the research team to extract the data collected will be recorded.