Here is the summary of the paper from the authors:

"💭 Why?

People on the autism spectrum and people with social anxiety can have difficulties in interpreting emotions of others. Their bodies also tend to react differently when observing others' emotion displays compared to people without these conditions. In addition, they tend to differ in how strongly they are aware of bodily reactions and in how accurately they judge them. We were wondering whether those differences are related to experienced difficulties in the interpretation of other’s emotions. In the end, mirroring another person’s emotion with one’s own body can make it easier to understand them.

👩🔬 What did we do?

We asked three groups of people - those with an autism (spectrum) diagnosis, those diagnosed with social anxiety, and people without either condition - to watch short headshot videos of people experiencing different emotions. While our participants watched the videos, we measured their facial muscle movements (to see if they mirrored the emotions with their faces) and their sweat levels (to see whether they got emotionally excited/upset). Later, we asked them to tell us, for each video, which emotion the person was experiencing and how strong this experience was.

🔍 What did we find?

People with social anxiety interpreted emotions quite similarly to people without a condition, and showed similar body reactions. However, they tended to see more sadness in others when they were more emotionally upset themselves. This was not as strongly the case for people without a condition. People on the autism spectrum had more difficulties in interpreting emotions of others, and also mirrored happiness less in their faces. Moreover, while people without a condition judged anger displays as more intense when they mirrored them more strongly, this did not occur in people on the autism spectrum. Here, difficulties in accurately sensing bodily reactions that people on the autism spectrum reported seemed to play a role.

💡 What’s the take-away?

People on the autism spectrum indeed seem to differ in how they experience others’ emotions. One difference may lay in the integration of feedback from the own body, such as changes in one's own face when mirroring others. Differences in interpreting others’ emotions seem to be more subtle in people with social anxiety. They may mainly occur when facing expressions that are more difficult to interpret, and when they are upset themselves, which easily happens in social situations in real life."