Doesn't show much?
- Is relationship quality THE ONLY thing that matters? Certainly it's very important, but individuals needs and wants, or desire to help other family members are not NOTHING. If drop in relationship quality was slight, but improvements to these other areas were pronounced, could be a trade off to consider?
- Couples were randomly assigned to each group and presumably ones who didn't adhere dropped out of study. Would the results be the same if decisions were made based on a heartfelt discussion, with agreement to try the other arrangement if the first one caused too much friction.
- Why is it an either/or? Is it a given that keeping a small "for personable hobbies" account while depositing most money in a family fund would hurt? Conversely, would rationally planning family needs and then keeping the rest of the money for personal enjoyment or treating each other with gifts/experiences be bad?
I am lucky enough to have inexpensive hobbies, so I can just spend of them as I wish and it's not going to move a needle on family finances. But if someone wants a family AND to climb Everest, I would not begrudge them not giving up on either dream.