Half of the time I can't do it consistently because of sensory issues. Every time I meet someone's eyes, I feel like my own eyes are becoming "full" and I have to look away before they "overflow," which experience tells me will lead to a partial shutdown (loss of visual processing ability, in this case). The other half of the time I just forget or become distracted by other things in view. I tend to focus on people's mouths if I do look at them consistently, unless they're fidgety, in which case I'll look at their hands. And I never thought about it, but I don't make eye contact while watching Youtube videos, either. Perhaps it mostly comes down to visual attentiveness. The tests I took for my assessment judged my skills in that area to be very low.
I can't make eye contact with families members, though. In fact, the more comfortable I am around someone, the less eye contact I make because I feel like I don't have to. Eye contact require a conscious effort most of the time, although if someone engages my attention very well, it begins to feel natural and I do it without thinking.
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I have not the kind affections of a pigeon. - Ralph Waldo Emerson