Traditionally, most autism assessment instruments are based on medical models and designed to identify social communication deficits and behavioral abnormality in an individual. However, as more autistic narratives reveal the insider views of autists, some scholars and autistic activists support the neurodiversity model and assert the acceptance of autism as difference and diversity instead of deficits or impairment. With this conceptual shift, it is appropriate to rethink the validity of current autism assessment practice. Adopting contemporary validity theories, which emphasizes the ontological definition of an attribute, response process, and ethical consequences of measurement, this study examined how autism has been defined, how the definitions of autism affect the way autism is understood and assessed, and how autism assessment affects the way people define autism. Also, as a case study, the current form of Social Communication Question was revalidated following Wilson's (2004) Four Building Block approach. The interview conducted with autistic adults and autistic people's caregiver to examine the response process revealed how these people interpret the items in SCQ and how autism assessment tools like SCQ have affected the way they conceptualize autism and establish their self-identities. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]