I have trouble recognizing people if they change their appearance (e.g., their hair, or wear glasses) or if they are in a place that I would not normally see them, like my mom at the airport, or a co-worker at the grocery store.
I've walked right past my mom at the airport on several occasions, because it's not her "normal environment". I recognize "Mom in her house" not "Mom at the airport."
I've also not recognized co-workers who changed their hair or were wearing glasses. The other day, I walked into the lab where I work and wondered, "who is that lady sitting at my boss's desk, using her computer??" I was about to introduce myself (a bit forcefully, since she was messing about in my boss's computer!) when i caught myself just in time. It was my boss, with her hair in a ponytail, wearing glasses.
I used to have a co-worker who liked to change her hair about once a month--hair extensions, braids, dye jobs, twists, coils, up-puffs, short short. She did a beautiful job, but every time she did it, it would take me a few minutes to decide if she was my co-worker or a client. It was like she had a head transplant every time. Happily, she started wearing a diamond nose stud on a regular basis, which helped me recognize her.
I'm better at recognizing voices, so I try to wait until someone speaks before I ask if I know them.
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Diagnosed Bipolar II in 2012, Autism spectrum disorder (moderate) & ADHD in 2015.