Note: these are the DEFAULT personalities given when you click on a star sign in Create-A-Sim. If you change the points around at all, the talent may be different.

Aries and Leo: Music and Dance
Gemini, Sagittarius, and Scorpio: Sports
Cancer and Pisces: Tinkering
Libra: Arts and Crafts
Taurus: Games
Capricorn: Cuisine
Aquarius: Nature
Virgo: Science
Bonus: If you use the 5-of-everything personality as often as I do, the natural talent is Cuisine.
I’m not sure that you can HAVE a natural talent in Film and Literature or Fitness.

it also bases on what they enjoy such as crime or food or school.

Any idea what the pattern is for sims born ingame? They seem to be assigned random astrological signs.

No, if you use the default personality for these star signs, I guarantee they will have the Natural Talent I listed. :D

Since interests change after a sim has been made, I don't think they have an effect.

I all depends on the personality points.

Most of my Sims are either outgoing / active or outgoing / playful (and they're all slobby and have about equal nice and playful / active points) and for these personalities, the hobbies are fitness (outgoing / active) and nature (outgoing / playful).

3-4 of my legacy Sims (born in game) have Fitness as their natural talent. I'm also playing HP's megahood, where Coral Oldie has a natural enthusiasm for Film & Literature.

Yes,, the personality points are key. For every possibly personality point combination, there is a specific Natural Talent.

But, my version is if you want ot make ABSOLUTELY SURE a sim has a natural talent in something, you can use the default starsigns to be sure.

(You can use cheats to change a sim's personality later, but I think their natural talent stays the same.)

...oops.

In that case, I'll find some personalities that create those and list them.

Thanks for the notification!

i remember that i made a house with one woman who had kids with various different men and every single generation/kid had the same hobby

I do have a natural talent in fitness, a born in game sim actually. She's a Gemini, neat 5 points, outgoing 10, active 9, playful 2, nice 6 (Thanks SimPe).

Don't know if this will help, but here's the spread on two of my Fitness Sims:

Tabitha (Gemini): Neatness 4, Outgoing 9, Active 8, Playful 3, Nice 3.
Raine (Sagittarius): Neatness 2, Outgoing 7, Active 9, Playful 7, Nice 4.

Oh, look, Nerina and I had the same idea. Looks like Outgoing and Active = Fitness.

As far as the Star signs, 4/5 in my Sim family are correct by your equation.. the only difference is that my Sim hubby is a Cancer, and has an unearthly talent for Games o_O

Well, maybe you didn't use the exact Cancer personality that comes when you click it in CAS?

Well, i'm only playing one family atm, and Claude the wife has Music&Dance and i chose her personality.
Meanwhile, i forgot to arrange Donny's personality so i have no clue what it is - i haven't checked yet. I still havent' discovered his predestined hobby.
I don't think it's cuisine, sports, tinkering, music & dance, arts & crafts, or Fitness.
But i may be wrong. :D

Snooty Sims have a whole page with the hobby/personality traits on it.

My sim Ashley has 3 Neat, 8 Outgoing, 10 Active, 8 Playful, and 6 Nice points, since she was born in-game, she has extra personality points, and her natural hobby is Fitness and Outgoing and Active seems to equal Fitness like you guys said.

No wonder all my simmies are music and dance... I like to give lots of outgoing points.

I have one sim that doesn't have a predestin hobby, he came with the game. his family came with apartments. anyways he's tried everyone, has points and those little green marks in every hobby but nothing that is a natural, no silver outline. the others in the house, all inborn sims, three our his kids. they all have differnt hobbies. So I'm not sure whats up with him.

Ah ha! No wonder one of my Scorp sims constantly goes for Sports. As a Scorpio, I've gotta say that I'm about as far from being sporty as is humanly possible, heh. I'd have picked art or literature, as most of the Scorps I know are artsy or writerly.