I've recently been thinking a bit about the nature of false modesty. When someone who is obviously superior in certain respects refuses to outwardly acknowledge such superiority, it begs the question... why?
Like most human actions, I am inclined to believe that modesty doesn't have a single common motivation. However, there are probably motivating factors which are common between individuals. I'd like this thread to be a discussion of those factors.
In some instances, modesty can be attributed to a miscommunication; that is, the person who is perceived as being modest is simply using a different metric to assess his/her own abilities. This different metric can be attributed to a different frame of reference or perhaps a different set of standards. As an example, I might acknowledge someone else as being a gifted tennis player (my abilities and knowledge of the sport are limited), but because they play regularly with professionals, they view themselves as below average (when compared to the very best in the sport) and thus disagree with my assessment.
Conforming to Social Customs
Rather than respond with a simple "Thank you," it is customary to display some degree of modesty when complimented. Since humans by nature seek to conform, this response has become the norm. However, since there must be some reason other than custom that someone was once modest (the first person to be modest couldn't have been following custom), there must be some exogenous factors at play as well.
Avoiding Confrontation / Self Preservation / Duality
There are some people who are superior, exhibit signs that they are aware of that superiority, but outwardly profess the contrary. While many of these people are perhaps motivated by other factors, I cannot help but think that a few of them are modest out of fear.
I think we can all agree that those individuals who are modest run less risk of being challenged on their abilities. To be overly expressive of a high self-opinion will most assuredly garner more scrutiny, but being modest elicits continued praise from others, and prevents such scrutiny. But... if someone fears being scrutinized, doesn't that mean they don't think they're that great? Not necessarily.
Many people exhibit a kind of mental duality with regard to self perception. They believe themselves to be far superior to others, but at the same time have a deep seeded fear that they are wrong in this judgment. Not necessarily that they are completely wrong about being superior, but that perhaps they are not quite as superior as they would like to imagine (Think 97th percentile instead of 99.999th percentile). There is a kind of comfort in being obviously superior, while at the same time not knowing the true extent of that superiority (to know is to be limited).