Which assessment primarily aids in the diagnosis of autism?

The correct choice is behavioral or functional assessment, which plays a crucial role in diagnosing autism spectrum disorder (ASD). These assessments focus on the individual's behavior and functional skills, including communication and social interactions, which are essential elements in identifying autism. They often involve direct observation, structured interviews, and standardized questionnaires that gather information from multiple sources, including parents, teachers, and the individuals themselves.

Behavioral assessments provide insights into how the individual interacts with their environment and peers, helping to determine patterns of behavior that are characteristic of autism. By addressing specific behaviors and their contexts, this assessment method can identify strengths and challenges, leading to a more accurate diagnosis.

The other options, such as intellectual assessments, physical health examinations, and standard IQ tests, do not directly target the unique behavioral aspects that are critical for diagnosing autism. While they may provide valuable information about cognitive abilities or general health, they do not specifically assess the communication and social skills that are the hallmark of ASD. Therefore, a behavioral or functional assessment is the most appropriate tool for diagnosing autism.