Process is a phone screen and a face to face interview. There is almost nothing about the interview that has anything to do with the role. You have to work through a maze of tests on conceptual thinking, operational mind set and thinking at the right "level." More than skills, they test to see if you can handle the unique "culture" of Bridgewater. You should review and understand the set of "principles" which is published on the web site. Have a few questions about the principles handy, it helps to look "smart." Note many have called it a "cult" not a "culture" and interviewing there pretty much tells you that. I interviewed in Research and everyone I spoke to was very smart and capable.

First round with HR. Second round is a group discussion. Given a topic, there is no right or wrong. I think they are trying to understand your thinking process and how you deal with problems.