Perceiving Emotions Behind Facemasks

How is it that we can discern somebody's emotions from their face, particularly their eyes?
Face Masks: Why Your Eyes Might Be Saying More Than You Realize
neurosciencenews.com/facemask...
Recognizing Emotion From Facial Expressions: Psychological and Neurological Mechanisms
pdfs.semanticscholar.org/05c5/...
Reading What the Mind Thinks from How the Eye Sees
doi.org/10.1177/0956797616687364