Why do you think causes some to show off and others to hide their achievements?

My dad knows a guy we met in an apartment building when I was 8 years old, the guy was unbelievably smart but I did not know they were intelligent until my 30s cause the guy never showed off or bragged. His son was one of the most intelligent guys in the province and I did not know he was intelligent until he was in his 20s cause he never once talked about his high 90s or his 100's in school to us, he just treated us like we were his brothers and sisters. When I learned he had a 98% average at one of the most difficult majors at Waterloo, and that he made $80,000 in 4 months at his first summer job at the age of 18 after finishing his first year of studies there, I learned he was intelligent. His sister was the same way, she was the top student in her grade and I had no idea she was smart cause she never talked about it. It was only after she won an award, that I learned she was smart.

Why do you think causes some to show off and others to hide their achievements?
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