'Introverts' are indeed scared of speaking up, in my case anyway, I know that I'm a sensitive guy so if I ever got laughed at it would hurt me more than your average person. I'm also not that big, so I'm kinda backing off of arguments. Well this my todays thinking anyhow. I think when I was a kid I probably had similar thoughts, just wasn't aware of it or couldn't explain it, because you know, you're not fully developed. But it hurts your confidence and outspokenness in the long term. I did have a large period of time that I WAS outspoken, until shit hit the fan. Anyway it's basically avoiding arguments with stronger bigger people than you - from an evolutionary and survival point of view logical. In todays world, it's partly logical, since we got laws and stuff. But that doesn't mean our brains, biologically, have changed along with society. Essentially, we're still the same human being we are thousands of years ago. Well, this is the case for me anyway. I do admit that I also tend to overstretch the situation in my mind. This is due to past events which weren't exactly fun and my trust in people has severely damaged. I quickly tend to think that any simple argument could lead to violence (which has actually happened to me). And I've learned people you're supposed to be able to trust will turn your back on you and go to extremes to make your life miserable. Introversion (if that's a word) has in my opinion indeed an underlying cause. You're scared of something, traumatized perhaps, and you don't dare to speak up anymore. It needs to be addressed. Something like self-defence sports could help.