Show of Hands

Depends on the individual.

Yes. A LOT of maturing goes on between 18 and 21...especially if you're in college.

Maturity level and thought reasoning

No

No, I think the biggest leap is between about 13 and 17.

Depends on their life experiences. I have known 19 year olds in the military that are older and more mature then a 40year old without military experience

Maybe slightly but not by much.

I was no less of an asshoIe at 21 than I was at 18.

Physically no. Mentally yes, because there are a lot of life changes that happen around those ages.

Most 18 year olds that I know are seniors in high school. Most 21 year olds have at least a part time job and some are in college. There is a lot of growing up when you juggle school, work and life away from your parents. So, yes. There are a lot of changes between 18 and 21.

Brain development and hopefully got responsibility.

I'd say so. I see it first hand because I teach many 18 year olds. Also, I've had three sons and they were very different at 18 than at 21.

Uh, yah. Especially brain development-wise. Though there would be a way bigger difference between an 18 and 23 year old.

Maybe, a person is typically more mature, having had a few years out of school and a little bit more experience living independently.
I am just tossing this idea into the ring for discussion.

Big? No

I am leaning no.