The investigators will assess the efficacy of Pivotal Response Treatment (PRT) in the treatment of communication deficits in children with intellectual disabilities. By collecting information about parent and child functioning before and after PRT, The investigators will be able to determine whether the intervention is effective in improving child communication and reducing parent stress.

Inclusion Criteria for Individuals with Intellectual Disabilities:

• Participants will have an age range between 2 and 17.11 years of age inclusive
• Male or female
• Diagnosis of an intellectual disability based on the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10), and an expert clinical evaluation
• have historical evidence of significant abnormal developmental milestones as determined by neurological history
• care provider that will reliably bring subject to study visits, and is trustworthy to provide accurate accounts of services provided to the subject

Inclusion Criteria for Individuals with Speech Delay/Language Disorder:

• Participants will have an age range between 2 and 17.11 years of age inclusive
• Male or female
• Diagnosis of a speech delay based on the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10), and an expert clinical evaluation
• Preschool Language scale (PLS) score of at least 1 standard deviations below age level (for children in the age range of 2-6.11)
• care provider that will reliably bring subject to study visits, and is trustworthy to provide accurate accounts of services provided to the subject

Exclusion Criteria:

• medically unstable (such as having unstable seizures)
• primary diagnosis of Autism Spectrum Disorder (ASD) is exclusionary as determined by the investigators