I think there is some generally universal moral that goes something like this: the larger and more intelligent an animal is, the more wrong we feel it is to hur

I think there is some generally universal moral that goes something like this: the larger and more intelligent an animal is, the more wrong we feel it is to hurt that animal. Given a choice between a lab rat or a chimpanzee, would you choose the rat over the chimp in the trolley problem? For people to feel OK with medical experiments, they want the risk to be in line with the intrinsic value they place on that life. Maybe lemurs are closer to the high risk category for most people, and they're better at predicting what will happen in the larger primate studies.