I'm almost positive that they're just trying to make themselves feel better. especailly, when they do it in front of someone, they're really just jealous!

I believe it a cover for inadequacies in other areas.

Both. Also, people who do that could be expressive people whose self-worth is based on recognition of their accomplishments.

If it's a constant form of expression, I'd say it's definitely a self esteem issue. People who are sure of themselves don't have to brag about their accomplishments to others. They speak for themselves;)

I think there could be several reasons. Some are doing just as you say to build up their self confidence. I think some people are very caught up with themselves.

Attention-seeking device, lack of self confidence and a sprinkling of fear of failure

Yes, I have no doubt self confidence and arrogance are two different things.

It depends on the person. Sometimes - especially in work situations - bringing up achievements increases the chances of a benefit (a promotion or raise, in the case of work). Some people like to brag and think of it as a contest, a sort of "biggest fish" story competition. And yeah, some people need validation and will seek it from anyone who happens to be in hearing range.

possibly a bit of both.

Another Name For Low Self-Esteem Is Pride: Many would assume that pride is over confidence or over active self-esteem. The outwardly arrogant nature of pride leads to bragging, boasting, and an overly defensive nature. Many people think the arrogant, bragging, boastful person struggling with pride really believes their boasts and is an overly confident person. But bragging, boasting and the easily offended nature of those overly defensive is not caused by too much self-confidence but a lack of self-confidence. If they were truly confident in who they were they would not have to brag, boast and be self defensive. They wouldn't have to tear others down to build themselves up. A person who is sure of themselves doesn't have to "prove" anything. Those who are confident and know who they are don't have to brag, look down on others to make themselves feel better, boast, nor be overly defensive when criticized. They can handle it. They are humble. They can admit when they are wrong. They know they are not better than anyone is and no one is better than they are. They don't have to prove anything to anyone or themselves. http://www.summit1.edu/gun17/gun02.htm People who lack in self confidence or self esteem always have the urge to prove themselves to others. To them, others appreciations are always better and more important than theirs. http://www.zachkong.com/personal-developement/why-is-it-important-to-recognize-your-achievement-and-its-effect-on-your-self-esteem As we study great men and great women from the perspectives of self-esteem and self-confidence, we see the attainment of both high self-esteem and high self-confidence by these great people. For example, Gandhi of India and Mother Teresa and when we trace to the earliest years when they embarked on their journeys to greatness, we notice that they were just like ordinary people. They may not have imagined the ultimate achievements they had made, but they had deep sense of their capacity to love and to liberate, and they had confidence at that earlier time to make some contributions or take small steps in the direction of their visions. They knew they have some deep sense of purpose in their life. They were humble and did not behave boastful in anyway, nor did they impose their values or standards on others, They just “did it anyway”! Over years they expanded or reinforced their capacity and capabilities, and they continued to achieve greater results. http://www.360q.com/NLP/Esteem.htm

I think it can be done both ways...some people have 0 self-confidence and do it for that...but then others *do* do it because they like the attention.

Both and it is very annoying and common place here.

Perhaps they struggled to achieve their success and would like others to share in their joy :)

If these people are doing so only occasionally, I would give them the benefit of the doubt and think they are merely trying to boost their lack of self confidence. However if they are constantly pointing out their achievements to others, I would think that they are trying to show off.