Barbarian building - dumb luck or tied to outside influence?

[Fahartle]

Hey all - does anyone know for sure if the barbarian cities build up according to some formula or outside stimulus? Or if it's just dumb random luck what they choose to build? I've read that if you attack them frequently they'll build walls, and I'm worried that they might build up the hiding place as well. I've read contradictory things on the forums. Does anyone know how this works for sure? I know we can destroy whatever we want with ballistas later (other than hidden stash), but I'm wondering if there's any way to "encourage" them to build the warehouse and resource generating buildings. Thanks in advance!!

[Tooltip]

I don't think you can encourage, you can only penalize them.

[Rob__TT]

I keep attacking same towns, I get good hauls and I take a battering ram too to knock down their wall. I send scouts out and the towns don't seem to expand resistance wise.

[Fahartle]

Yeah, I haven't noticed any differences in progression - I'm hitting a dozen of them regularly and they build all sorts of different things. I think it's random.