[Kevin]

I think it has to do with the collective memory of each individual chapter. Speaking for NIC groups, it seems that the 'culture' of individual chapters is most predictable by looking at when the chapter was founded. Chapters founded before the 50's seem to have a vastly different character than chapters formed in the 80's, and chapters founded recently are nothing like the other two.

The reason for this I think is that a chapter gets its personality through traditions. Traditions are upheld by active alum involvement and of course, they're passed down through actives.

When a chapter is founded, new traditions are created (having founded a chapter, I helped establish a few of these myself). These traditions are passed down through the membership as something that they just 'assume' must be done -- and let me tell you, it's amazing to see traditions that you thought up as something 'fun' to do at a given moment still being practiced several years after you graduate -- I fully expect them to be doing so 20 years from now.

Because of this, I think that throughout NIC groups at least, you'll find more similarities between chapters founded around the same times belonging to different organizations than you'll find similarities between different chapters of the same organization.

I can't speak for NPHC, but it seems that they have a more collective culture. By that, I mean that there is more socialization between members of their different chapters, and therefore, more traditions in common, and therefore more uniformality between chapters. That's my theory anyhow.