I believe that it is that third option. She is intellectually gifted, and she likes to learn things on her own, too.

ALM
Threadkiller.

I see it as, a desire to progress, she wants to acheive more and more. Either that or, a general fear of regret. Afriad of looking back and knowing she could have done more. I know for a fact there are people like this in real life so, its not a case of 'creating the perfect girl', which is why, Lisa has the depth that gives her so much attention.

ALM
Threadkiller indeed!

On-topic:
I think Lisa inherited most of her good merits from Marge. In the recent seasons, Marge acts more like Homer (maybe he finally affected her?), but in the older episodes, Marge sometimes acted very much like her older daughter. What can I say to Lisa? Never marry a guy like Homer Also, Marge's childhood looks very similar to Lisa's sometimes (even if we don't know much about it) - loneliness, misunderstanding from the others, much of work...

I think her brains is a gift from birth supported by her constant brain exercises she makes for herself everytime. I'm not so envy to her intellect at this times (I was in past ), and now I see first of all her spiritual qualities. What anyone can develope no matter of the present IQ. But, what to say, to talk with her would be a problem for me (maybe...or maybe not ). There's two differences between the business dialogue with her and easy conversation for relaxation. For the first is ok for me as like with most of the people, second case would be quite problematic
I still curious how would she react at me if we meet and had a talk. She tries to be equally unprejudiced with a new and unknown people. And as long as she goes to understand who's she sees, she can change her mind properly. But she perfectly knows her own value, and the recent story with Milhouse getting orphane proves that she can change her attitude to man almost in seconds, just you be "appropriate" to her. What I don't know how to estimate, really. From one side she did inconstant and it's not so good. But I clearly support her with it. It is just reasonable - to treat someone by his value and acts.

It was Brooks who pitched the character for Lisa when starting the series, all Groening had during the shorts was that she was just a girl version of Bart, Brooks pitched that Lisa should play an instrument, Silverman suggested that she plays the Tuba (much like he does) and it was quickly changed to the sax. Groening had only made minor character personalities up until 1989, the writers then fleshed them all out in the writers room.

Brooks gives orders to Groening because he owns the company that makes the show, i.e. Gracie Films, so Groening is second in command on the show only to Brooks. This is why the episode "A Star is Burns" aired. Brooks liked it, and Groening didn't, Groening had his name removed from the credits. Brooks was able to go over Groening and get the episode aired.

Well, although Lisa was more "bratty" in the Ullmann shorts than in the actual show, she was always smarter than Bart. And who knows, if the producers would have decided to age the characters over the time, Maggie might have grown to the genius that Lisa represents now.