I discretely observe groups of people socialising while on trains or in cafes etc., trying to understand better what they are doing, and one of my current interests is in the openness or closedness of faces.
I'm perplexed by the attitude of health professionals to the idea that people with ASD are poor at non-verbal communication, and what the significance is of eye contact. Professionals do not seem to see why we have trouble with it. I wonder if people are reading too much into what individual eye movements or facial expressions are saying directly. Perhaps we ought to explore whether what is being conveyed is less concise and more about reasdiness to talk.
Groups of younger people tend to show more facial expression changes. As people grow older they become more reserved about this. I do wonder if one reason young people on the spectrum find it easier to talk to older NTs is that they demand less facial expression change.
An open face, it seems to me, is attentive to social exchange. The frequency and variety of facial movements is quite high, and these are encouraging responses from others. They keep saying "come on, speak to me".
Eye movements, eyebrow movements, different smiles, as well as open arm/hand gestures (hands several feet apart) are conveying they want to hear what the other person has to say.
The actual changes in expression don't seem to be so critical, and different people have different types of expression. It is more about how often these occur.
I've observed that if the connversation runs dry this mechanism is still operating, which may be why people say "wot?" other than deliberately in fun, because the other persons face is still beckoning a reaction, as is theirs.
When I observe people I suppose might be on the spectrum, they often have fixed facial expression. They aren't making these "come on" facial changes. Also they tend to lean forwards and appear challenging or aggressive, and go straight into a dialogue. When I've observed these situations (not to mention experienced them directly), there aren't any preparatory high frequuency facial changes, and the other person's response, being uncertain and wary, or even purposefully not wanting to start a conversation, is equally lacking "openness".
Where NTs become agitated, or aggressive, there is also a dramatic reduction in the frequency of facial changes. While the face conveys challenge, it does so fixedly - a "closed" face.
Therefore I suspect with ASD we often convey challenge rather than "come on - chat to me".
So the reaction of an NT to someone with ASD may not be so much what they say, but a lack of openness signals (and a lack of ability to see the NT isn't conveying openness).
Also, if it is this simple, it may be something that we can learn to emulate or do better.