I'm beginning to think that Savage had a nice idea here that just didn't pan out as well as he had hoped, with statistical significance. It's so hard to tell when we have only journalistic tripe to work with. It would be a bad assumption that the quotes reported were accurate or in context. He was studying altruism (the lynchpin of society in animals) and the cultural (learned behavior) overlay in a crisis environment holding mixed "groups" (where the classifications are arguably arbitrary or poorly chosen.)

Although he is called a behavioral economist, this is the stuff of animal behaviorists and population biologists. The mongrel group called "Americans" had a more diverse gene pool and a formative, "adolescent" culture, while being the largest "group." Scandinavians presumably had the tightest genetic relationships, in a smaller group. The British of the day may have been suspected to be the ones with the strongest cultural rules and norms.

He may well still believe that he could show, with superior test design, that cultural aspects of British behavior disproportionately affected results that would have been predicted by population biologists, or somehow became a relevant factor enhancing or diminishing theoretical predictions from Darwinian modeling at the group level.

He did find, he says, statistically significant groupings by group size, passenger class, sex, age and fitness. It seems though, that group size, passenger class (and probably Americans communicating in the dominant language, I would guess) swamped lesser classifications, notably national culture, relegating them to statistical insignificance.

"Be British, boys" may have inspired his hypothesis and "Americans proved pushy" may have inspired newspaper editors, but all in all it is interesting reading.