[throwitawayday]

The correction:

“Empathy and pro-social behavior in rats” by I. B.-A. Bartal et al. (9 December 2011, p. 1427). On p. 1428, the last full paragraph of column 1 was incorrect. The paragraph should be replaced by this corrected text: “All female rats (6/6) and most male rats (17/24) in the trapped condition became door-openers. Female rats in the trapped condition opened the restrainer door at a shorter latency than males on days 7 to 12 (P < 0.01, MMA, Fig. 3A), consistent with suggestions that females are more empathic than males (7, 12, 13). Furthermore, female rats were also more active than males in the trapped condition (P < 0.001, ANOVA) but not in the empty condition (Fig. 3B).”

[jonlucc]

Odd to me is that they use 24 males and only 6 females. In my work (which is biology), we would usually use the same group size unless we had reason to know better.

For example, there's a new-to-us model that we think might have differences between strains, sexes, and vendors. We ordered in 8 mice of each type to run a pilot.

[semi-extrinsic]

So they used 30 rats in total?Any numbers on how statistically well-powered this was?

[dogma1138]

30 rats are plenty if they selected them properly - different gene pools, different breeders etc...

[saalweachter]

You wouldn't necessarily care about genetic diversity for this sort of experiment. This experiment isn't trying to say "all animals" or "all rat species" exhibit this behavior; the interesting thing is that any animal does.

[tremon]

For me, the more important question is not whether all test subjects were genetically diverse: it's more important that the free rat and the caged rat are dissimilar. The situation would be vastly different if the rat pairs were related, since there is a genetically selfish motivation for caring for those within the same gene pool.

[jonlucc]

This becomes apparent when you try to co-house rats and mice. Litter mates are much less likely to fight.