It's mainly people coming up behind me unexpectedly or appearing unexpectedly that startle me. I often scream when this happens, which is somewhat disruptive at work. At my last job I had a mirror by my computer so I could see people coming behind me (especially as I was often wearing a headset or earphones), partly because a lot of people got a kick out of startling me and making me scream. One time when I was married my husband at the time opened the door while I was in the shower to join me (assuming I heard him out there, I guess, and I shrieked and started crying. I was very startled). I think it comes from the fact of me being in my "own world" and the other person thinks I would have noticed them by now, but I haven't. Note: I am not a screamer at other times, such as if I'm in a regular scary situation, then I tend to choke up. Things like mice or bugs, etc don't really startle or scare me, or at least, they don't make me scream, though I might jerk reflexively if I come in close contact unexpectedly.