What can vampire bats teach us about human cooperation?

I have been asked this question several times by journalists and people during outreach events. So here’s my answer:

If you really want to understand human cooperation, you should study humans. Specifically, we should study how humans cooperate with each other under natural circumstances across a wide diversity of cultures. And we should manipulate the factors that we think drive natural forms of human cooperation to see if we can make cooperative behaviors go up and down. Such experiments must be smarter than the participants. It’s no good to merely ask experimental subjects “How much would you sacrifice to help a stranger in situation X?” and expect that the person won’t take into account the very real potential costs and benefits of being watched or judged, and the fact that the sacrifice is hypothetical and not real. The experiments must also not interpret confusion as choice. For those interested in evolved human nature, the experiments must also be natural enough to mimic scenarios that would have been important throughout our evolutionary past. Human brains might not be designed for one-shot anonymous economic interactions, just like we are not built for social isolation (or perceiving faces as inside out).

If you want to understand the evolution of cooperation more generally, you need multiple approaches, including both theoretical and empirical work with a diversity of organisms. Vampire bats are just an interesting piece of that complex puzzle.

Of course, studying vampire bats won’t tell us how humans cooperate. But they might give us general insights into how cooperation works in a long-term social relationship. This is simply because, compared with people and other primates, cooperative relationships in vampire bats are easier to measure and manipulate.

Vampires groom and share food with each other in a small dark corner of a cave or tree, which can be simulated in captivity. They are small, so you can easily house many in a lab space. In that way, they are a bit like highly cooperative lab rats. And do not underestimate what we have learned about humans from rodents! Obviously, we can do experiments with bats and rodents that we can’t do with humans. But by using simple tractable “model organisms” like monogamous voles, we have also gained extraordinary insights into the biological basis of complex behaviors such as romantic attachment and empathy.

Finally, and paradoxically,  I think it’s often easier to understand cooperation in a strange alien system like bats, because I am less self-deluded about how well I understand them. The study of humans always comes with the curse and blessing of being the subject. Like every human being, I have powerful intuitions about myself and about human nature: I think I understand human cooperation way more than I actually do. I think I know why I do what I do and why I care about what I do, but I don’t really. I’m overconfident that my subjective experience gives me some direct insight into my own and others’ cognition and behavior. We have intuitive folk wisdoms and ideologies about human cooperation that must be largely discarded before we can even think clearly about it.

With vampire bats, it’s easier to admit ignorance. I only have hypotheses about the function of their behaviors, not ideological beliefs. I have no idea how they think, or how similar or different they are to people. It’s a total mystery. The only windows I have are the experiments.





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