What is the difference between YA and Adults in the Sims 3?

Well, on the physical side of things, adults do have age lines on their faces especially noticeable on the forehead and a bit around the eyes. They are also a teeny bit slower than young adults in their movements. However, the biggest difference I have noticed is that adults are more behaviorally 'settled down' than the younger Sims when it comes to how they handle social and personal relationships as-well-as trauma events.

Also with adults; the naso-labial triangle is more pronounced on their face as opposed to “Young Adults” - you see the opposing diagonal creases by the side of the nose - that’s the naso-labial crease.

If Generations is installed, adults will get the mid life crisis moodlet and the game will prompt all sorts of wishes for sudden changes like switch houses, jobs, divorce...

Adults have a lower fertility rate in general and are also able to suffer a Midlife Crisis when aging up with generations based off how their young adult life went.

Plus a few wrinkles here and there, but nothing major visually!

The head models are different.

To illustrate just one example, here's a generated Bridgeport bouncer with most of his sliders not too far from their default positions. I drew the mouth slider to its lower extreme position in order to show what that one does.
https://i.imgur.com/n3Om0y7.jpg
Note how the mouth sagged downward in the full adult sim, and the philtrum (the cleft in the middle area of the upper lip) became very prominent.

That's one of the pitfalls if you create your sims as YA's. In YA's, the mouth height slider does almost nothing, whereas it has pronounced effects on the head models of teens, full adults and elders.

In addition to the wrinkles mentioned above, adults have more shriveled cheeks and lips, which is obvious at the CAS when switching age.

"mw1525;c-18098208" wrote:
However, the biggest difference I have noticed is that adults are more behaviorally 'settled down' than the younger Sims when it comes to how they handle social and personal relationships as-well-as trauma events.

I'm all ears?

Yeah. Thanks guys.I already knew the main mechanics, like midlife crisis and lower fertility rates, just looking for appearence changes.

I found out the main appearence change. Adults Sims have a noticible lined jaw, wheras young adults it's absent.

"Turjan;c-18112916" wrote:
The head models are different.

To illustrate just one example, here's a generated Bridgeport bouncer with most of his sliders not too far from their default positions. I drew the mouth slider to its lower extreme position in order to show what that one does.
https://i.imgur.com/n3Om0y7.jpg
Note how the mouth sagged downward in the full adult sim, and the philtrum (the cleft in the middle area of the upper lip) became very prominent.

That's one of the pitfalls if you create your sims as YA's. In YA's, the mouth height slider does almost nothing, whereas it has pronounced effects on the head models of teens, full adults and elders.

Thanks.

Okay. CAS doesn't show any wrinkles for some reason...