Thanks for the informal post! I really liked it, and probably wouldn't have read the whole paper.
I have a few thoughts that I'd be curious for your take on.
I'm a bit unsure how generally the papers you're looking at apply to the broad question of changing values. A few intuitions:
These papers look at measurable and relatively narrow features of the past, and how far they explain features of the present which are again measurable and relatively narrow. My intuition would be that most of what matters in terms of values is pretty hard to measure, and might not show up in very concrete slices of reality. But maybe this is confused: if there were big fuzzy effects, they would show up in narrow concretisations?
Naively I'd say that past values and culture have had a huge impact on current values and culture. Many religions have persisted for a long time, there are differences in values between cultures that seem to have been relatively persistent, everyone inherits a bunch of assumptions from their society many of which have been around for a long time... (Below, Lumpyproletariat makes a similar point I think.) If all of my ancestors were Chinese, I expect I would see the world quite differently to how I actually do, with European ancestors. I don't really understand how intuitions like this relate to your findings. Do you have any ideas?
To progress, we’d need to study the cultural legacy of intentional movements. This is a much harder topic, where quantitative proxies will be hard to come by.
Do you have any ideas about how to make progress on this? E.g. examples of intentional movements that seem worth looking into, proxies that might work...?
Thank you Rose! You make interesting points, let me try to reason through them:
These papers look at measurable and relatively narrow features of the past, and how far they explain features of the present which are again measurable and relatively narrow.
This is a point worth grappling with. And let's be fair - there are many obvious ways in which cultural transmission clearly has had an effect on modern society.
Case in point: Xmas is approaching! And the fact that we have this arbitrary ritual of meeting once a year to celebrate is a very clear and measurable example of a cultural value being passed down through generations.
And yet, all these studies fail to find any strong effect in their analyses. What is going on?
Here are two possibilities:
a) cultural transmission mostly affects abstract social values like religion or political tendencies but not concrete personal values like trust.
b) abstract social values are easy to measure and quantify; concrete personal values elude a precise quantification.
I do certainly think that there is some truth to hypothesis b). It is easy to ask people about religion and note down their answer; it is harder to measure trust except in very superficial ways. The studies on trust rely on imperfect proxies like surveys.
I still think that hypothesis a) has more explanatory power. It is consistent with the literature on parental transmission, where my rough impression of the consensus is that children tend to culturally inherit abstract beliefs from their parents but not behaviours, which are mostly dictated by the shared cultural context and genetics.
Here is an excerpt from Bryan Caplan's Selfish reasons to have more kids (pp. 45):
Parents have a big effect on religious labels, but little on religious attitudes and behavior. Parents strongly affect which religion their children say they belong to. A major study of over 7,000 adult Australian twins finds that identical and fraternal twins are highly and equally likely to share a religion—precisely what you would expect if nurture mattered a lot and nature didn’t matter at all. Another study of almost 2,000 women from the Virginia Twin Registry reaches a similar conclusion: Family has a big effect on religious denomination, while genes have at most a small effect.
[...]
Twin and adoption research reveals surprisingly little parental influence on how truly religious children grow up to be. One early study of almost 2,000 adult Minnesota twins reared together and apart found little or no effect of parenting on religiosity. Researchers measured the twins’ interest in both religious activities (such as attending services, volunteering, and religious study) and religious occupations (such as being a minister, priest, rabbi, missionary, or religious writer). Identical twins were much more similar on both measures than fraternal twins. Nurture effects were small for religious activities and zero for religious occupations. A recent follow-up found similar results.
My impression is that the same goes for politics. I do not know if other belief / attitude clusters have been studied, but I think it would be a safe bet to think they would have found the same pattern.
Of course, bear in mind that I am no sociologist. So take everything I am saying with a dose of healthy skepticism.
Do you have any ideas about how to make progress on [studying the cultural legacy of intentional movements]?
There is a large corpus of historical analysis studying social movements like the suffragettes or the slavery abolitionists. My bet is that there would be large value in summarizing their learnings and taking an "eagle's-eye view" to look for interesting patterns in this movements. How long did it take since the movement was conceived until it spread? How did the main ideas originate? Can we build "infection models" of cultural ideas, making retrospective predictions of eg how many people supported LGBTQ+ rights each year? My outsider perspective is that there is very few people / teams working on the intersection of qualitative analysis and history of social movement, so I expect plenty of low hanging fruit there.
Within the community there has already been some work on summarizing historical movements. For example, Nuño Sempere talked about the Spanish Enlightment and General Semantics here, Holden Karnofski summarized ALL HISTORY here and Alex Hill and I wrote about the history of women's rights and animal rights here. I would like to see more work on this vein, and more actual historians participating in the community.
Snodin and Kinniment's research on succesful technological fields is also relevant, as an example of the kind of history-flavored, "eagle's-eye view" research I think the EA community can excel at.
Regarding specific movements I would personally be interested in studying more closely: animal rights, feminism, the abolition of slavery, the Enlightment, the Scientific revolution, nazism, major religions and Russell's rationalism are easy examples of cultural movements that became widely successful at some point and will be good to look at from an "eagle's-eye view" perspective. Finding failed social movements to study is harder, though identifying a collection of them would be a great project for an early career researcher.
Another tangential topic I am interested in learning more about is cultural transmission in the near term, eg from grandparents to grandsons. Will the grandchildren inherit 1/4th of the variation of the cultural values of their grandparent relative to their respective cultural environments? There surely must be studies on the topic, though I haven't looked closely.
So, can we influence our great great great grandchildren's values? The answer is a very scientific and very disappointing maybe.
This made me laugh out loud. And then I found out I can take partial credit!
In all seriousness, the jokes and turns of phrase definitely contributed to me finishing the article, so it's already working on me at least. :)
Also, great title choice! I predict that question-based titles will be especially good for the forum, being both engaging and in keeping with EA culture.
Again, emphasis on small. The causal effects identified in the papers were in the range of about 0.1 standard deviations of the outcome per standard deviation of the exposure. That is, if you worked hard to move culture in a particular direction, I would expect at most 10% of the change you bring in to persist in future generations.
It is plausible that smaller effects exist - which we would not have enough statistical power to detect. It is unlikely that stronger effects exist, since those would be easier to detect. And I would correspondingly have expected to be flooded by papers studying how your ancestors' religion explains your Netflix watching habits.
Perhaps the similarity between areas is caused less by the effects being small, and more by cultural dispersal and diffusion? I know that my ancestors, the early Christians on the Mediterranean, had a huge effect on my culture today. But since they had a similarly huge effect on the descendants of Brits and Swedes, that might not be very visible if you compare their geographic place of origin with other parts of Europe. In fact, I'm myself also descended from the British Isles; the descendants of the Classical inhabitants of Iberia are also the descendants of Classical "barbarians". I've read that it only takes ~1,500 years for someone to become the common ancestor of all Eurasians. (Link goes to where I read it, not the original source which I haven't followed up on.) Weak observed effects of medieval culture on Italian cities may be less that cultural effects decay, and more that modern Italians have ancestors from every city on the peninsula.
I think this is a good point and worth emphasizing.
The studies are focused on studying variation across populations - if everyone in the studied population is equally affected by the cultural forces in question, then this will not show up in the results.
This still means that in practice deliberate cultural interventions are less appealing. In this interpretation, you cannot work towards improving the values of a subpopulation and hope that they will persist through the time - the forces of dispersal and diffussion, as you say, will slowly wilt away the differences.
In order to effect deliberate change, you will need either a very convincing reason to believe that the change you are introducing will survive cultural diffussion, or a mechanism for affecting a very large population.
Intuitively I would expect persistence effects to be weaker now than e.g. 300 years ago. This is mostly because today society changes much more rapidly than back then. I would guess that it's more common now to live hundreds of kilometres from where you grew up, that the internet allows people to "choose" their culture more freely (my parents like EA less than I do), that the same goes for bigger cities
etc. Generally advice from my parents and grandparents sometimes feels outdated, which makes me less likely to listen to it — this may always have been true of young generations, but I feel the advice really is more outdated today than it would have been 300 years ago. In short, I would expect to be much more influenced by my grandparents if I were running their farm with basically the same methods.
This is all super speculative of course and I don't have any hard evidence (other than economic growth rates being higher). But do you agree that there may be reasons to expect this effect to have decreased by a nontrivial amount?
Demographics are a major factor in determining the values of future generations. Currently, the demographics in the US with the highest fertility rates tend to be insular religious fundamentalists like the Amish, certain groups of Mormons, and Ultra-Orthodox Jews. Because of these demographic trends, it's plausible that religious fundamentalists will become demographically dominant during the 2100s. Robin Hanson talked about this in his article The Insular Fertile Future. Eric Kaufmann has also talked about this in his lecture Why the religious will inherit the earth.
As for possible ways to preserve modern/WEIRD values, Robin Hanson suggested trying to create new subcultures that have cultural traits that result in high fertility, but also inherit most of their cultural values from modern/WEIRD culture. With enough experiments involving creating new subcultures, high fertility subcultures that preserve modern values might be created.
EDIT: Faatima Osman questioned whether it was fair to exclude respondents from Benin, Ghana and Nigeria in Nunn and Wantchekon's paper, given that Nigeria is the most populated country in Africa by far.
And in hindsight I think she is totally right - respondents from these countries are ~25% of the sample! I now believe that its unfair to call these respondents outliers. Correspondingly, my trust in Nunn and Wantchekon's paper has gone up, since Kelly's critique was my main concern about it.
The book Albion's Seed seems relevant here (see Scott Alexander's book review). It argues that modern American regional variation in culture/politics can be traced back to the cultures of the people who immigrated to differents areas - Puritans, Quakers, Borderers, and Cavaliers.
Before I had any idea about any of this, I wrote that American society seems divided into two strata, one of which is marked by emphasis on education, interest in moral reforms, racial tolerance, low teenage pregnancy, academic/financial jobs, and Democratic party affiliation, and furthermore that this group was centered in the North. Meanwhile, now I learn that the North was settled by two groups (quakers and puritans) that when combined have emphasis on education, interest in moral reforms, racial tolerance, low teenage pregnancy, an academic and mercantile history, and were the heartland of the historical Whigs and Republicans who preceded the modern Democratic Party.
And I wrote about another stratum centered in the South marked by poor education, gun culture, culture of violence, xenophobia, high teenage pregnancy, militarism, patriotism, country western music, and support for the Republican Party. And now I learn that the South was settled by a group (borderers) noted even in the 1700s for its poor education, gun culture, culture of violence, xenophobia, high premarital pregnancy, militarism, patriotism, accent exactly like the modern country western accent, and support for the Democratic-Republicans who preceded the modern Republican Party.
I haven't read the book (obviously) but it seems to focus more on qualitative historical arguments rather than quantitative. Did you come across any studies that have looked at british-US immigration patterns over historical timescales and how that might have affected modern day culture and social outcomes in these areas? This could be a good natural experiment to look at for intergenerational persistence studies as you got a rapid influx of immigrants from one religious/social subculture who were essentially able to start from scratch in a new region with limited immigration from people who were not in that subculture (not many puritans/northerners probably moved to the south/appalachia for much of 1700s/1800s).
"Albion's Seed" is a fabulous book. If you are interested in how material history affects value or American history in general, it is a must read. To save time, take a look at my summary of this book:
Hello, I am a member of the Progress Studies community. The original poster posted in our Slack channel. I am cross-posting so you EA can see it. There is in fact a huge and growing literature on the historical impact of current economic development. I think it is one of the most exciting trends among historian. You mentioned a few articles, but there are far more. In addition, there are dozens of awesome books that at least touch on the subject. I want to point out that this literature is about UNDERSTANDING the present by studying the past. How ACTIONABLE the conclusions is less clear. I do believe that a study of history is the only way the we can increase our chances of making positive contributions to the future. The biggest impact is letting us understand what has been tried before and the results of those actions as best as we can tell. Even if all we learn is that an idea has been tried before and the results were poor, that is of HUGE benefit. You seem more interested in values than material conditions. I would encourage you to expand your interests to material conditions. Material conditions strongly influence values. I have a summary of just a few of them in my online library of book summaries. I think it is a very useful resource for EA research. In some ways, all 280 books summaries are relevant to this question. https://techratchet.com/effects-of-history-on-economic-development-learning-path/ (edited)
In the Progress Studies movement, I am trying to cultivate an interest in studying history at a deeper level. I think this would also be relevant to EA.
If you are interested in following up, send me a private message in the Progress Studies Slack channel.
I am glad that you point to the Morgan Kelly article on potential flaws in the quantitative methods used by "Persistence" field. Keep in mind the Persistence field is only a TINY part of the overall literature on the historical impacts on the present. Typically, the Persistence field applies heavily quantitative methods to one small region and focuses on testing whether one potential cause has statistically significant effects. Because of their methods, it should not be surprising that you come away unimpressed at the narrowness of the findings. Unfortunately, that is often how academia works. But there has been a huge number of fantastic books which explore the historical impacts of the present using largely qualitative methods. They are, in other words, good reads about big topics. I would like to think that my book is one of the better ones. I think that the broader literature a much better introduction to the subject that the Persistence field. I linked to some examples in my previous comments. I believe that my online library of 280+ books is a great resource for EA to quickly understand the basics of the literature and then figure out how they might apply it to action. https://techratchet.com/
This is a crosspost from the new Animal Welfare Alignment Newsletter by Anima International. You can subscribe on Substack if you are interested in following these efforts. Audio reading also available on Substack.
The goals of this post are to:
1. Raise a question I see as crucially important to the goal of aligning AI to animal welfare...
Hello! I'm Justin Portela. I got hired by GWWC to make YouTube videos after AI in Context did such a kickass job.
My channel is using that same cinematic, high-production value beauty to talk about everything in the EA universe that isn't AI.
...
This is a linkpost for Request for Proposals: Research and Applied Work on Digital Minds.
I'm glad to announce a request for proposals for research and applied work on digital minds at Longview Ph...
The preprint is blowing off my charts with thousands of visits. So I thought I would share more thoughts while the iron is still hot.
In this post I write more informal comments - my personal takeaways. Take these as more informed by my intuition than by hard evidence.
You have been warned.
In short
Intergenerational persistence is an important topic for Effective Altruism. It can help us understand how our actions today can affect people many generations later. For example, I want to know if promoting truth and cooperation today can persistently affect the values of future people.
The Forethought Foundation hired me to review seven papers on these sorts of persistent effects. These papers study things that may seem a bit... outlandish. Examples include a) the relation between the agricultural tools used by your ancestors and modern gender attitudes; b) whether descendants of Africans in places raided by slavers are less trusting; and c) whether descendants of early Catholics are more individualistic.
I'll admit it - I had a strong bias against intergenerational persistence when I started. With all due respect to my grand-grand-grand-grand-grand parents, I found it hard to believe that they have influenced me very much. So on I went, hunting for how the researchers had managed to mess it up.
After engaging with the literature, I have reluctantly changed my mind. Many papers I reviewed had some methodological issues, yes. But I also found careful, robust and reasonable analysis on some key papers. Short of manufacturing the data, I don’t see how they could have got such strongly significant results otherwise.
I now believe that there is a small degree of intergenerational persistence of values. Emphasis on small - if the effects were bigger I would have expected to see more dramatic examples in the papers.
So sorry grand-grand-grand-grand-grand mother - seems like I owe you a bit more of my heritage than I thought I did.
It is still not clear to me how the transmission actually happens. Is it because of parents teaching their children who teach their children and so on? Parents founding institutions that locked-in their values? Parents etching sternly worded reminders in family heirlooms?
Most papers I reviewed argued the transmission was primarily about parents-teaching-children. However, they rely on historical and psychological evidence I don't feel comfortable evaluating.
It is also not clear whether the persistent effects stay constant or diminish with time. I'd expect the latter - if only because I have 4 grandparents, 8 great-grandparents and 16 grand-grand-grand parents. So naively I would expect any effect to dilute with each successive generation.
My impression of the papers in a nutshell
Schulz et al paper on religion, kinship and psychological variation puts up a strong case for cultural transmission. They look at how places where the Catholic Church was established earlier areWEIRDer (particularly, more individualistic). But as the authors point out we are not sure of the causal mechanism. It likely has something to do with religion and how families are structured. But the data studied in the paper is not enough to tell whether the correlation is causal.
Nunn’s previous work on slavery and economic variation is suggestive. He looks at African countries that were specially affected by slavery, and finds that those countries have relatively lower GDP today. But the analysis is underpowered, the causal analysis stops being significant after controlling for precolonial prosperity and the mediation analysis is not conclusive. According to a paper cited by Nunn, slavery cut the population of Africa in half - this must have messed up economic development in all sort of ways beyond changing cultural values.
Unlike with movies, the sequel was better. Nunn and Wantchekon’s study on slavery and trust finds that descendants of people in areas of Africa that were more affected by slavery exhibit lower levels of trust. Economist Kelly Morgan pointed out that Nunn and Wantchekon's results are no longer significant if we exclude respondents in Benin, Nigeria and Ghana (which are specially low on trust and have a very slavery-intensive past). But those are 25% of the sample, which is such a large fraction that calling them outliers starts feeling more suspicious. Regardless, I could not rule out a spurious correlation.
I mostly do not trustGuiso et al’s study of the independence of medieval Italian cities and modern measures of civic capital. They look at how Italian cities that became independent city-states during medieval times donate more, are less likely to cheat on high school exams and are generally better neighbours. I was not able to find the city of origin of the researchers, so I cannot unduly accuse them of a conflict of interest here. But I can definitely bring up that their proxies for civic capital are contrived and the results are not very robust. With one exception: I could not find any issues with the results that relate medieval independence to receiving a gold medal for heroic resistance against the nazi regime in WW2. But they analyzed this outcome in less depth and with less nuance in the paper. Aside, I falsified their proposed mediation mechanism (“self-sufficiency”).
(in what I can only assume is a deliberate effort to make my life more difficult, the data for Jha's paper was not and as far as I know still is not publicly available - and Voitlander and Voth's somehow decided to use different non-standard methods for each result they present. Alesina et al’s paper was less troublesome, though they are to blame for having me google "plow hoe sex" in what must be the most naive search ever)
All in all, I would bet there are some small persistent effects
Again, emphasis on small. The causal effects identified in the papers were in the range of about 0.1 standard deviations of the outcome per standard deviation of the exposure. That is, if you worked hard to move culture in a particular direction, I would expect at most 10% of the change you bring in to persist in future generations.
It is plausible that smaller effects exist - which we would not have enough statistical power to detect. It is unlikely that stronger effects exist, since those would be easier to detect. And I would correspondingly have expected to be flooded by papers studying how your ancestors' religion explains your Netflix watching habits.
Since the effects identified are at the border of the sensitivity of our current methods, it is unclear how significant they are. Better tools and tests would help address that issue.
Lacking these future methods, we have to speculate. My guess is that there must be some small cultural parent-to-children persistence. This guess is mostly based on a hunch that the results are underpowered more than biased. Also, I see religion as a credible proof-of-concept for cultural persistence ; it is ripe with many rituals and customs that have survived through generations. Other people I have talked to have different opinions on the whole issue.
We do not know whether persistent effects tend to vanish
There just hasn’t been much research done on the topic as far as I can tell. This is a crucial question for longtermism - a sort of “discount rate” for culturally persistent interventions.
Just from looking at the seven papers I reviewed, there is no evident pattern. Maybe the variation stays the same, maybe it diminishes with time or maybe it traces a cosine wave whose oscillation period matches the lunar phases. Intuitively I would bet that it diminishes with time, but this is based on a hunch rather than hard evidence.
Are my values influenced by all my immediate Spanish ancestors to the same degree than by my more distant Medieval Catholic Spanish, Muslim Andalusi, French, Portuguese and Moroccan ancestors? Seems unlikely. Image source.
We do not know whether cultural persistence can be triggered on purpose
All the papers I reviewed study persistent outcomes that were not deliberately sought.
In some of those cases the changes that brought the initial variation were quite extreme - for example enslaving enough people in Africa to halve (!) the population of the continent.
Thus even if cultural persistence is possible, the events that lead to it might not be realistic to deliberately trigger in practice.
To progress, we’d need to study the cultural legacy of intentional movements. This is a much harder topic, where quantitative proxies will be hard to come by.
We need more open reviews of persistence studies papers
Not to point fingers, but as a relative outsider to the field, I was able to add significant nuance to the analyses conducted in these widely cited papers.
This points to a gap in the field around reviewing each other’s work, replicating previous work and performing more robustness checks.
Kelly’s recent work is an example of this. I expect further analysis to reveal more issues. So you know what to do if you are an econ grad student looking for something to work on.
Research on persistence is hard
There is a mixed bag of results that are plausible and results that do not hold up under scrutiny. Most of the results I looked into find a statistically significant correlation, but many of the analyses of causation and mediation are not convincing.
As a telltale sign, the results I found more convincing involved natural experiments and studying children-of-immigrants.
I was surprised to learn from Kelly's work that the slavery and trust analysis did not stand up after removing respondents from the Bight of Benin. While I think this critique does not ultimately hold water, this makes me hesitant about my results. I think that if other researchers attempted replicating them they would find more issues.
So, can we influence our great great great grandchildren's values? The answer is a very scientific and very disappointing maybe. Definitely not by much - and we have little idea of the best mechanisms for doing so. I am waiting for Kelly to publish his next paper and turn every persistence result on its heels again. Meanwhile, why not check out my full paper?
Nuño Sempere reviewed a previous version of the original post I prepared for the release ofthe preprint, and his comments convinced me of writing a more informal post as well. Faatima Osman helped me with editing, and pointed out a critical flaw in my results. Ronja Lutz provided superb editing and feedback. I blameKat Woods' post for all the terrible jokes I have inflicted upon you over the course of this article.
Thanks for the informal post! I really liked it, and probably wouldn't have read the whole paper.
I have a few thoughts that I'd be curious for your take on.
I'm a bit unsure how generally the papers you're looking at apply to the broad question of changing values. A few intuitions:
Do you have any ideas about how to make progress on this? E.g. examples of intentional movements that seem worth looking into, proxies that might work...?
Thank you Rose! You make interesting points, let me try to reason through them:
This is a point worth grappling with. And let's be fair - there are many obvious ways in which cultural transmission clearly has had an effect on modern society.
Case in point: Xmas is approaching! And the fact that we have this arbitrary ritual of meeting once a year to celebrate is a very clear and measurable example of a cultural value being passed down through generations.
And yet, all these studies fail to find any strong effect in their analyses. What is going on?
Here are two possibilities:
a) cultural transmission mostly affects abstract social values like religion or political tendencies but not concrete personal values like trust.
b) abstract social values are easy to measure and quantify; concrete personal values elude a precise quantification.
I do certainly think that there is some truth to hypothesis b). It is easy to ask people about religion and note down their answer; it is harder to measure trust except in very superficial ways. The studies on trust rely on imperfect proxies like surveys.
I still think that hypothesis a) has more explanatory power. It is consistent with the literature on parental transmission, where my rough impression of the consensus is that children tend to culturally inherit abstract beliefs from their parents but not behaviours, which are mostly dictated by the shared cultural context and genetics.
Here is an excerpt from Bryan Caplan's Selfish reasons to have more kids (pp. 45):
My impression is that the same goes for politics. I do not know if other belief / attitude clusters have been studied, but I think it would be a safe bet to think they would have found the same pattern.
Of course, bear in mind that I am no sociologist. So take everything I am saying with a dose of healthy skepticism.
There is a large corpus of historical analysis studying social movements like the suffragettes or the slavery abolitionists. My bet is that there would be large value in summarizing their learnings and taking an "eagle's-eye view" to look for interesting patterns in this movements. How long did it take since the movement was conceived until it spread? How did the main ideas originate? Can we build "infection models" of cultural ideas, making retrospective predictions of eg how many people supported LGBTQ+ rights each year? My outsider perspective is that there is very few people / teams working on the intersection of qualitative analysis and history of social movement, so I expect plenty of low hanging fruit there.
Within the community there has already been some work on summarizing historical movements. For example, Nuño Sempere talked about the Spanish Enlightment and General Semantics here, Holden Karnofski summarized ALL HISTORY here and Alex Hill and I wrote about the history of women's rights and animal rights here. I would like to see more work on this vein, and more actual historians participating in the community.
Snodin and Kinniment's research on succesful technological fields is also relevant, as an example of the kind of history-flavored, "eagle's-eye view" research I think the EA community can excel at.
Regarding specific movements I would personally be interested in studying more closely: animal rights, feminism, the abolition of slavery, the Enlightment, the Scientific revolution, nazism, major religions and Russell's rationalism are easy examples of cultural movements that became widely successful at some point and will be good to look at from an "eagle's-eye view" perspective. Finding failed social movements to study is harder, though identifying a collection of them would be a great project for an early career researcher.
Another tangential topic I am interested in learning more about is cultural transmission in the near term, eg from grandparents to grandsons. Will the grandchildren inherit 1/4th of the variation of the cultural values of their grandparent relative to their respective cultural environments? There surely must be studies on the topic, though I haven't looked closely.