When I was younger, 10-15 years old, I would look in a mirror and recognize myself. Then, for a few seconds, I would not know who I was looking at. It was a little spooky than but it has not happened since. Anyone have any explainations for this? Is this common?
Is this common? I haven’t heard of it before, but I’m only a sample of one.
Why does this occur? One possible explanation is that you’re just plain nuts, but you’re probably looking for a different answer. (The rest of you can stop reading, recognizing the correct answer when presented.)
Actually I don’t know the answer except to say that recognizing faces is a complex process – i.e., there are lots of places for it to go a little bit haywire. IIRC, there have been stroke victims who have lost the ability to recognize friends and family.
Possibilities: 1) Some little part of your brain was out of whack for a while – not the whole recognition part but the self-recognition part. 2) There was some psychological reason for you to reject the mirror image and it took a little while for the conscious part of your thinking to overcome the subconscious part.
The fact that you were an adolescent when this happened and that it stopped when you got older seems to be significant to me. If my possibilities are at all correct, I would guess it is 2). Adolescents have a lot of self-esteem issues, body image being a big one. Maybe there were changes in your appearance that were somehow frightening to you (subconsciously) and you didn’t want to acknowledge that that person in the mirror was you because you didn’t want to look like that.
FWIW I am now, and have been for quite some time (~15 yrs), pretty heavy. When I was young I was skinny. I’m still surprised when I look in the mirror: “Who’s that fat guy?”. My skinny self-image is so durable that it persists years after it stopped being remotely correct.
Happens to me.
I look in the mirror, and I stare at some part of my body, then I look at my eyes and think “uh oh did he just catch me staring?” and then i realize its me
I’m insane though
But why, when you look in a mirror, are left and right reversed but not top and bottom? Spooky! 
Martin Gardner has explained that in his book The Ambidextrous Universe. It’s actually back and front that are reversed, not left and right.