We live in a time when “resting bitch face” is a joke, selfies are constant, and activist art implores us to stop telling women to smile: We’re as aware of our faces as ever. But the conversation still largely excludes people who don’t always have control of theirs: people with a flattened affect.

In psychology, the word “affect” refers to someone’s variability in facial expression, pitch of voice, and the use of hand and body movements, according to a University of Washington Department of Psychiatry glossary. A person’s affect can be “broad” (which is the norm), “restricted” or “blunted” (which both mean pared back in some way) or “flat”: lacking signs of affective expression, or having a monotonous voice and unmoving face.

Think about the time you’ve wasted wondering if you made an awkward face when trying to remember if you knew that person you ran into on the street, or if you scrunched your eyebrows too much in that job interview. For people with flat affect, emotional expression is limited, reduced, or nonexistent. This isn’t an illness or a disorder in its own right but a possible symptom of many brain conditions, such as depression, Parkinson’s disease, autism, traumatic brain injury, and schizophrenia, according to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-V).  more