Looks like: Focused on single topics to the apparent exclusion of outside facts, perspectives, or the world around them.
There are times when getting lost down the rabbit hole of research is an expression of dysregulation, but unless their emotional state looks distinctly effected, it’s very common for some to become so absorbed in topics of interest they can “disconnect” with the world for stretches of time.
The Reality: Good ole’ hyperfocus and/or autistic inertia! Many have the ability to focus on their subjects of interest intensely, making connections that others may miss.
Not every autistic/ADHDer experiences this, but they can develop a keen intuition about their areas of interest, and often come up with creative problem solving.
When burned out or severely dysregulated special interests can turn into a coping mechanism, but this is still a healthy, typical experience.
It may feel rude when an individual is lost in this world, but giving space for the exploration, cues that a change of topic is approaching, and time to help them “reel in” their thinking cap, is the best chance at engagement with a willing participant.