A lot of people both on and off the spectrum agree that an autistic's facial expression doesn't always match their emotion. Sometimes people will think someone looks mad when they simply have a straight face. I find this interesting, and recently had such an experience.
I was talking to someone who wanted to share something that was on their mind. As they talked, I listened. I got stuck at one point as I did not have much knowledge or any experience with what they were talking about, and didn't know what else to say. They told me I looked "concerned." As far as I know, I was keeping a straight face. I wanted to seem approachable and didn't want the person to feel put off when I got stuck, so I kept the same expression and just listened as I tried to best to give my input. How I looked concerned, I don't know!
I also get people asking me "what's that look for?" My mom asks me this frequently :P I guess I must have a certain expression when I'm deep in thought or trying to concentrate in something and don't realize it. I'm someone who can only focus on one thing at a time, so when I'm focused on something I'm doing, I must not be able to focus on what face I'm making! XD
Has anyone else had any experience with this? I'd like to hear your stories :)