Evidence for Learning Recall T0 T1 Prestigebiased imitation
Evidence for Learning
Recall…
T=0 T=1 Prestige-biased imitation (a. k. a. cultural evolution): More successful individuals more likely to be imitated/teach than less successful individuals.
T=0 T=1 Reinforcement Learning: More successful traits held more tenaciously than less successful traits. Key common assumption: more successful becomes more frequent
We use to justify why our behavior—and corresponding beliefs/preferences—are consistent with Nash Some individuals mutate H Row H Player H H H D D D Column D Player D H D D D D H H H D H U H D D D
Here is a bit of evidence for reinforcement learning…
BF Skinner shapes behavior in a pigeon
Now a bit of evidence for prestige-biased imitation…
First study shows that chimpanzees selectively imitate prestigious individuals
Horner V, Proctor D, Bonnie KE, Whiten A, et al. (2010) Prestige Affects Cultural Learning in Chimpanzees. PLo. S ONE 5(5): e 10625. doi: 10. 1371/journal. pone. 0010625 http: //www. plosone. org/article/info: doi/10. 1371/journal. pone. 0010625
Horner V, Proctor D, Bonnie KE, Whiten A, et al. (2010) Prestige Affects Cultural Learning in Chimpanzees. PLo. S ONE 5(5): e 10625. doi: 10. 1371/journal. pone. 0010625 http: //www. plosone. org/article/info: doi/10. 1371/journal. pone. 0010625
Horner V, Proctor D, Bonnie KE, Whiten A, et al. (2010) Prestige Affects Cultural Learning in Chimpanzees. PLo. S ONE 5(5): e 10625. doi: 10. 1371/journal. pone. 0010625 http: //www. plosone. org/article/info: doi/10. 1371/journal. pone. 0010625
Strong evidence in humans, too…
Chudek et al (2011) show that 5 year olds imitate prestigious individuals more
Step 1: Show subjects video of “prestigious” model getting attention, and another getting ignored Step 2: Show both models expressing preferences over food, artifact, beverage, etc. Step 3: Elicit subjects’ preferences over these categories
More evidence… Studies of workers show that people disproportionately look at the most powerful person in the room and imitate how they sit In interview advice, explicitly advocate imitating your interviewer (presumably because makes them feel prestigious) And, obviously, advertisers regularly exploit prestige-biased imitation
Summary so far: showed evidence that behaviors are learned
Next… Cultural evolution (learning/imitation) leads to highly functional behavir
How to build an igloo VS. “ 1845…Franklin…two field-tested, re-enforced ice breaking ships equipped with state of the art steam engines, retractable screw propellers, and detachable rudders. With cork insulation, coal-fired internal heating, desalinators, five years of provisions including tens of thousands of cans of food (canning was a new technology), and a 1, 200 volume library” Stranded on King William Island cannibalism all died “…King William Island lies at the heart of Netsilik territory, an Inuit population that spent its winters out on the pack ice, and their summers on the island, just like Franklin’s men. “
“One morning in 1998, when I was living in rural southern Chile and working with the indigenous Mapuche, I arrived at my friend Fonso’s farmhouse to find him preparing what he called mote, a traditional Mapuche corn dish. He showed me how you have to scoop fresh ash out of the wood stove and put it into the corn mix for soaking, before heating it. ” Why do they put ash in their corn?
“…A diet based on corn can leave one short on niacin (vitamin B 3). Failure to get enough niacin results in a disease called pellagra, a horrible condition characterized by diarrhea, lesions, hair loss, tongue inflammation, insomnia, dementia and then death” “…To release this niacin, populations throughout the New World culturally evolved practices that introduced an alkali (a base) into their corn preparations. In some places, the alkali came from burning seashells (generating calcium hydroxide) or the ash of certain kinds of wood. Elsewhere, there were natural sources of lye (providing potassium hydroxide). Mixing the alkali into the recipe in the right way chemically releases the otherwise unavailable niacin in the corn”
Do you think the Mapuche understood this? “I thought that was curious, so I asked him why he mixed the wood ash in with the corn. His answer was “it’s our custom. ” Conclusion: Social learning can lead to highly functional behavior no one in the community “understands”
When don’t understand, might expect to imitate even things that don’t appear essential. Indeed, we evolved to overimite
Finally, evidence that all this is mediated by preferences and ideologies…
Our Thesis We assume… behaviors (via corresponding preferences/ideologies) which yield higher payoffs become more frequent through evolution, imitation, and learning E. g. , TFT (via gratitude, eye-for-an-eye) is more than paid back and becomes more frequent Then… behaviors (and corresponding preferences/ideologies) emerge that are consistent with Nash E. g. , TFT (via gratitude, eye-for-an-eye) will emerge
Our Thesis We assume… behaviors (via corresponding preferences/ideologies) which yield higher payoffs become more frequent through evolution, imitation, and learning Are preferences and ideologies learned? E. g. , TFT (via gratitude, eye-for-an-eye) is more than paid back and becomes more frequent Then… behaviors (and corresponding preferences/ideologies) emerge that are consistent with Nash E. g. , TFT (via gratitude, eye-for-an-eye) will emerge
First piece of evidence…
In Fiji, pregnant women adopt food taboos that protect them from sickness based on superstition “the violation of [food taboos] is perceived to carry social or supernatural sanctions” Source: Henrich and Henrich 2010
Fijian Food Taboos
Consensus grouping are most likely to carry Ciguatera, a dangerous toxin
Poisoning falls during pregnancy
Whom Fijian women learned the taboos from:
Recall we claimed that there is no need to be aware of the function learned behaviors Fijians illustrate this: women simply believe gods will smite them for eating taboo foods
More evidence, this time on food preferences…
Spiciness People’s preferences for spices varies from location to location Source: Billing and Sherman 1998 and 1999
Why? Is this just random? No. Spices have a function…
Spices are used most where they are most useful
(Also… dishes with meat usually spicier than vegetarian dishes)
Again, people use spices because they like the taste, not because they know of their antibacterial power Evidence: usage patterns persist after the introduction of refrigeration
How do we know food preferences are learned? Lots of evidence. For example: Children of immigrants adopt local tastes
Our Thesis We assume… behaviors (via corresponding preferences/ideologies) which yield higher payoffs become more frequent through evolution, imitation, and learning Are preferences and ideologies learned? E. g. , TFT (via gratitude, eye-for-an-eye) is more than paid back and becomes more frequent Yes. Then… behaviors (and corresponding preferences/ideologies) emerge that are consistent with Nash E. g. , TFT (via gratitude, eye-for-an-eye) will emerge
- Slides: 50