Early Infantile Autism is characterized by which of the following?

Early Infantile Autism, which is now generally referred to as Autism Spectrum Disorder (ASD), is indeed characterized primarily by impaired social interaction and communication. Individuals with this condition may have difficulty understanding social cues, developing relationships, and engaging in typical verbal and nonverbal communication. This can manifest as difficulty in sharing interests or emotions, challenges in understanding social norms, or the inability to engage in conversations.

In contrast, the other options focus on aspects not directly linked to the core characteristics of autism. Impaired physical health doesn't specifically define autism, as individuals with autism can have varied health statuses. Increased tolerance to stress is not a recognized feature typically associated with autism; rather, many individuals with ASD may face heightened anxiety and stress in social situations. Episodes of dissociation are more related to other psychological conditions and not to autism specifically. Therefore, the correct characterization of Early Infantile Autism aligns with the social and communication deficits outlined in answer B.