I think serious is not a part of the intelligence and also lighthearted with dumb...
Intelligence is a gift, so either you have or you don't. That doesn't mean that if you don't have it that you can not build it. Eating organic food, reading good books, playing strategies games, hanging out with intelligence people and many more things can really help you to build your intelligence. But, don't forget that having a high IQ can damage your mental power. People who are highly intelligent usually have problems with the emotions or there EQ is low.
Lighthearted people are those who usually have excellent EQ. But, keep in mind that having a high EQ and low IQ can also bring you to a mental problems. That's why you have to keep balance between this 2 coefficients. I am telling you this from my personal experience... Before 4 years my IQ was 164 and now is 145, but my EQ level is now much better and I feel emotionally stable.
![Wink](https://bitcointalk.org/Smileys/default/wink.gif)