Insert horrified looks when I tell me friends some "funny stories" from my childhood. :D
When half my concentration in a given conversation goes to behaving "properly" (trying not to fidget, maintaining a hopefully appropriate amount of relaxed eye contact without staring, appearing attentive but relaxed), half goes to figuring out whether, how, when and what to contribute and I also have to listen and process the words because I occasionally struggle with understanding spoken language... yeah, sure, I may seem normal, but something somewhere is gonna drop off the radar.
Whether I say something appropriate or hit the right timing to chime in without either interrupting or being too late becomes (even more of) a gamble, which stresses me out and causes anxiety, further taking away focus and composure. Alternatively, I become quiet and feel more like an observer on the sidelines than a part of the conversation, isolated by my own struggles. Or I blunder and say something wrong and retreat to that isolation in shame. Or I don't really hear what you're saying, lose track of the conversation, am caught off-guard by the odd question cast my way, or simply retreat from trying to contribute because I don't even know what we're talking about, back into the same isolation.
I'm a chatty person. But I'm scared to chat with most people. Doing so leaves me either mentally or emotionally drained and upset. I hide away, retreat to the internet where I can better regulate my participation, make excuses not to attend company events, let social contacts slip away because maintaining them is too much stress, struggle to make doctor's appointments or call for a med refill...
If you think I seem normal - thanks for the compliment, I worked really hard on that facade. I'm glad it's working.
But inside, I die a little each time.