I can do it, too, when the person isn't speaking for long periods of time, so the whole exchange becomes non-verbal and through the eyes.
People on the spectrum often don't talk as much, so eye contact becomes easier because, on its own, it takes up all of my processing capacity. When there's verbal and eye contact going on at the same time, eye contact is too overwhelming, because I cannot discern what the person is saying at the same time. Many people can switch quickly from one channel to another, but I cannot or it's very exhausting to do so.
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Leading a double life and loving it (but exhausted).
Likely ADHD instead of what I've been diagnosed with before.