Assessment and intervention in Autism and related disorders has become a major application area for the field of Behavior Analysis. However, basic behavioral research and research in other applied areas have recently provided new insights into the nature of language and other complex human behavior that although directly relevant to autism may not be widely known due to the volume of currently available literatures. This paper provides a review and synthesis of recent research on conditional discrimination processes and relational responding in humans, research on a possible hierarchy of discriminations as described by the literature on the Assessment of Basic Learning Abilities (ABLA), and the implications of this research for language acquisition in person with autism and related disabilities.