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Reputation holds cooperation together - but not at the scale of global problems. See also "Origins and Psychology of Human Cooperation" w/ Joe Henrich: 6/6

The local group are people you interact with regularly. They affect your life the most. They should care more that you're a good neighbor, friend, or family member than a climate change activist. Key result: Local cooperation should undermine global cooperation when in conflict. 5/

Nepotism, cronyism, and other forms of corruption aren't failures of cooperation - they *are* cooperation, but on a lower scale. Our new model extends P&B (2004) but puts people in 2 groups - a local group (L) & a global group (G), w/ the choice to contribute to either or none. 4/

The problem is that the model assumes we belong to one group, w/ one reputation. We don't. The manager hiring his cousin is a bad manager but a useful family member. The official who lets a friend bypass the visa queue is a bad civil servant, but a good friend. 3/ Paper:

In a landmark Nature paper, Panchanathan & Boyd (2004) developed an elegant model showing how reputation can sustain large-scale cooperation: we prefer to help those who've contributed to the public good. If I know you're a patriot or support climate action, I'm more likely to help you elsewhere 2/

🚨 PNAS paper: "Indirect reciprocity undermines indirect reciprocity destabilizing large-scale cooperation" w/ Eric Schnell How do we achieve global cooperation on climate or conflict reduction? The problem isn't selfishness as much as it is cooperation itself - at a smaller scale. 1/

The leading theory for why animals evolve big brains is social: Bigger brains manage bigger, complex groups 👫👬 👊🐙 Octopuses break that rule: mostly solitary, no parenting, and still the smartest invertebrates alive. 🧠 So why the big brain? Taking a look at a new study. 🐙 Thread 🧵(with sources)

Thank you to my co-authors - PhD / postdoc leads Kiran Basava & Theiss Bendixen; lead RA Alexander Leonhard; fab RA team Nicole Lauren George, Zoé Vanhersecke, Joshua Omotosho, & my co-PI and cephalopod expert Jennifer Mather. Data & code: github.com/kcbasava/... 13/13

What next? More data are needed. Higher-resolution measures of calories & complexity: temperature, latitude, oxygen, predators, prey, competition and measures of brains beyond size. Data here: https://cephdata.com 12/

Brain data also only exists for 79 of ~820 living cephalopod species, and whole brain size misses lobe structure/neuron counts. The available species do span a wide range of sizes, habitats, & phylogeny, and sensitivity checks were consistent, but even so we don't have data for 90% of ceph. 11/

Important caveats: data and phylogenetically controlled models alone don't tell you the causal mechanism. That's why formal theory is useful - you can model assumptions and logic for possible mechanisms. A lot of the paper explains the role of theory in helping us interpret non-causal analyses. 10/

Sociality is the main difference b/w the ABH and SBH. SBH predicts more social species should have larger brains. Sociality was not reliably associated w/ larger brains - in fact perhaps the opposite. 9/

Depth also indicates shallower-living species tended to have larger brains. This fits the idea that shallower habitats are generally more calorie-rich, biodiverse, & more cognitively demanding than open-water habitats. Again, consistent w/ the ABH. 8/

Results: consistent w/ ABH, ecology predicted brain size. Sociality didn't. The strongest predictor was habitat: cephalopods living on or near the shallow seafloors had larger brains than open water species. The relationship was enormous, ~2/3 as large as the body-brain size relationship. 7/

We preregistered the ABH predictions against the Social Brain & compiled the largest comparative brain dataset for cephalopods yet: 5 years 79 species 3,933 papers 115 variables coded a new phylogeny brain size, body size, ecology, sociality, & behavior 6/

The Asocial Brain Hypothesis says that while trial and error learning is less efficient than social learning, bigger brains can be favored when the environment is rich and complex enough that intelligence unlocks more calories & avoid predators. 5/

Sociality can't explain cephalopod brain size, so what does? First, it's worth knowing that evolution favors the smallest brain that let's you survive and thrive, because brain tissue is expensive (about 20x as expensive as muscles in humans). So it has to be worth paying the energy bill 4/

Prior to the CBH, the dominant theory for the evolution of large brains was the social brain hypothesis - brains evolved to cope w/ the demands of group living. Cephalopods are smart - use tools, solve problems, deceive - but they're short-lived, die after reproducing, & even cannibalistic. 3/

Here we got around to testing this "Asocial Brain Hypothesis" in cephalopods - octopuses, squids, & cuttlefish - by spending half a decade building the most comprehensive database & test of their brain evolution yet. 2/ Paper: www.sciencedirect.co... Press release: www.lse.ac.uk/news/e...

🚨 New paper in iScience: "Ecological not social factors explain brain size in cephalopods" In 2017, we published the Cultural Brain Hypothesis, a model of human brain evolution. It made an unexpected prediction: non-social animals could evolve big brains too, if their ecology was rich enough. 1/