I don't think there's one model that covers 1) and 2) like you're saying. I think two very different mental processes are going on, and we only use the term "belief" for both of them because we've committed the <a href="http://www.overcomingbias.com/2008/02/compress-fallac.html">fallacy of compression</a>.

That is, "I believe (in) X" can mean either

1) My mental model of reality includes X.

or

2) I affiliate with a group that centers around professing X [so I've got a gang watching out for me and if you're part of it we have a basis for cooperating].

So, I don't think there's one answer for your question, because you're describing two different processes, with different methods and goals. Choosing beliefs type 1) is the process of seeking actual truth, while type 2) is the process of gaining power through group affiliation.

Or maybe Robin_Hanson's cynicism is rubbing off on me.