Tuesday, January 27, 2009

Overpopulation of Urban Deer lecture notes

I wish that it had taken more of an economic perspective, but the environmental science was interesting nonetheless. The thrust of the problem is that deer populations are staggeringly high and it is causing problems for biodiversity, creating more deer-vehicle crashes (which are deadly), aiding the spread of lime-disease carrying ticks to new regions, and generally annoying suburbanites.

Why has it happened? Overpopulation of herbivores is rampant all across the globe. Other examples include Canada geese, elephants, feral pigs, and gypsy moths. Our man-made landscapes provide ample food for deer, and most of the natural predators have been eliminated. The extra nitrogen added to the soil due to the herbivore feces accelerates the nitrogen cycle which is beneficial to some plants but harmful to others, reducing biodiversity.

What can we do about it? Relocation of deer is one possibility, but it is basically futile because it is stressful to the deer and 80% of them die within a year. Contraception has been largely ineffective in the wild, although it is an appealing option. Fencing works, but is expensive to implement and maintain, plus it just displaces the burden onto your neighbors. Reintroducing natural predators is another choice that wouldn't pass city council because most people aren't as tough as Bear Grylls.

The best option, according to The Nature Conservation, has been increased "culling", which is the politically correct word for hunting. This has been successful in the areas they have introduced it, although they have had strict regulations. Although some of their hunters use rifles, apparently many of them use bow and arrows, which is amazing. The speaker quoted a fact that there has never been a recorded death due to archery-based hunting of deer! That is change I can believe in.

Bottom Line: Add "learning archery" to your list of green-friendly activities, and curse the plight of overpopulated urban deer unabashedly.

Monday, January 26, 2009

What drives your actions?

This is a topic that I ponder constantly. Marvin Minsky offers the most succinct answer I have ever heard in The Society of Mind,
None of us enjoys the thought that what we do depends on processes we do not know; we prefer to attribute our choices to volition, will, or self-control.... Perhaps it would be more honest to say, "My decision was determined by internal forces I do not understand."
As an example, I will offer some trends in my behavior that I cannot fully explain: Why my blogging tends to come in chunks, Why it takes me so long to take a shower when I come back from the gym, Why I still have not synced my iPod with my computer so that I can listen to podcasts, Why I decided to major in neuroscience, etc.

In general I find that I have more trouble to explain big life decisions than smaller ones, which is too bad because generally all anyone else cares about is my reasons for the big ones. If you would like to know why I wear Asics running shoes, I could come up with some solid answers. But nobody has ever asked me that!

Saturday, January 24, 2009


Will Wilkinson rants:
In the debate over economic stimulus, I hear many otherwise brilliant people making a lot of baseless conjectures about mass psychology — about consumer and creditor “fear” and “uncertainty,” and what to do about it. But, as far as I can tell, none of them has even a rudimentary theory about the causes of micro-fear or how it scales up to aggregate consumer demand or aggregrate credit supply, etc...

Nevertheless, I hear economists saying things about how easy money is needed to soothe investor worries, about how a surge of government spending is needed to quell consumer anxieties, about how the government’s “doing nothing” would cause people to panic and make everything worse, and so on. Do any of them have any idea what they are talking about when they say these things? I’m afraid they don’t. And, frankly, I think they should be ashamed of themselves.
Like usual, I agree with a lot of what Will is saying. Monetary and fiscal stimulus have become such an expected response to recession that perhaps the best way for the government to restore consumer confidence would be to do nothing, signaling that no stimulus is even necessary.

One problem is that the politicians in power have an incentive to make the situation appear worse than it really is. That way, if the solution fails they can deflect the blame onto the situation itself. I believe we have a massive principal-agent problem on our hands, with politicians focused more on applause lights and showing care than on the actual results.

Tuesday, January 20, 2009

Benchmarks for Obama's Presidential Success

"Remember Red, hope is a good thing, maybe the best of things, and no good thing ever dies." - The Shawshank Redemption

Lower the National Debt
: There are many ways that Obama could accomplish this: Cutting back on "wasteful" spending, ending the war in Iraq, slashing entitlements, ending the war on drugs, whatever. This is a blanket category for simply lowering the national debt as a percentage of GDP. At the end of the third quarter of 2008 (October 1), the national debt was $10,024,724,896,000 (from here), while the GDP was $14,412,800,000,000 (from here), for a percentage of debt of 69.6%. Assuming that the debt of other countries has stayed constant since 2007, that would put us at the 18th highest level in the world (based on this). Here are some possible futures:

Debt as a percentage of GDP above 75% = F
Debt as a percentage of GDP less than 75% = D
Debt as a percentage of GDP less than 69.6% = C
Debt as a percentage of GDP less than 65% = B
Debt as a percentage of GDP less than 60% = A

Slash Per Capita Healthcare Spending so as to be Comparable to OECD Countries: This should be done while maintaining health outcomes as comparable to these countries. Here is the most recent data (taken from here, OECD countries defined here, explanations on data techniques here):

The US is currently the worst in the world at this category with comparable countries. The median on this list is currently $3187 per capita. In 2005 (the most recent statistics), our value was 200% of this median. If after Obama's presidency that number is,

250% or greater = F
220% or greater = D
180% or greater = C
150% or greater = B
Less than 150% = A

If there is an accompanying dramatic reduction or improvement in health outcomes, which I would not expect, then I will use my discretion to factor that in. I expect that the WHO will collect this data sometime near 2012.

If Obama's GPA is a 2.5 or above, I will consider him a "good" president, if he gets a 3.5 or above I will consider him a "great" president. This post was inspired by the inimitable Robin Hanson's proposal here. Check back in four years from today for the results.

Saturday, January 17, 2009

The Real Best Picture

Much hoopla has been made about Slum Dog Millionaire winning Best Picture at the Golden Globes and the fact that it currently has a 75% chance of winning the top prize at the Oscars as well. Lost in all of the scuffle is the fact that the people have already decided on the best movies of the year, via imdb.

The Dark Knight is the best movie of 2008. It has a rating of 9.0 out of 10, while Slumdog Millionaire has only an 8.7 out of 10. The Wrestler is next with an 8.7 as well (position on the top 250 breaks the tie), followed by The Curious Case of Benjamin Button with an 8.5, Gran Torino with an 8.3, and Milk with an 8.1.

The number of votes on each of these movies is astounding. Each of the movies mentioned has well over 10,000 votes. The Dark Knight has 332,333. That's more than the population of the Bahamas!

Who cares what some snobby industry insiders think? The Oscars are an anachronism, having been replaced by the will of the people.

Friday, January 16, 2009

The Utility of a Social Network

Dora Costa and Matthew Kahn discuss some of the research on social networks, and they come up with the following nuggets:
  • The most important factor to minimize desertion from companies in the Civil War was having a homogeneous unit, meaning similar types of people (I assume this means ethnic and geographically.)
  • About 75% of men who joined the Salafi Jihad did so with their friends or family or because a close friend was already involved. Apparently the ideology was rationalized only later.
  • Those who lack a social network (ie, self-report as socially isolated) have a higher risk of death from certain viruses, cancer, and heart disease. The explanation is that they have more stress.
What if all of your friends are joining a quasi-militant movement that you do not agree with? You must either conform or face serious consequences--not only emotionally but also physically.

Perhaps the ultimate utility of a wide social network is that you can always afford to let a few friends go their own way without taking too much of a hit.

Thursday, January 15, 2009

Tuesday Statisticz: Foreign Ratings of US Comedies Part I

In Creative Destruction, Tyler Cowen argues that
Movie producers know that action films are easiest to export to many different countries. Heroism, excitement, and violence do not vary so much across cultures. comedies, with their nuances of dialogue and their culturally specific references, are the hardest to sell abroad. A global market in cinema therefore encourages action films more than it does sophisticated comedy.
Previously this would be based on intuition, but with imdb's huge data corpus we can now make it empirical. The null hypothesis is that the US and non-US samples do not differ significantly. Should we reject it?

So as to not bias my sample based on the trash that my friends and I enjoy watching, I randomly sampled 2 movies from each decade since the 1960s from Wikipedia's list of US comedies using this random integer generator. Movies were re-generated unless they had at least 2000 total votes. I also generated 10 US movies from the 1960s on from the action category from the Wikipedia's list here.

The preliminary data suggests that there is no significant difference between the ratings. The mean US ratings for these comedies is 6.91 and the non-US mean rating is 6.71, but due to the high standard deviations (.80 and .89), the difference is not significant with a two-tailed t-test (p=.604). The mean US ratings for the action films is 6.22, SD 1.097, and that for the non-US ratings is 6.13, SD 1.025, which is clearly also not significant.

My work is not nearly complete, because I think there were some serious flaws in the methodology. These are the questions I will contemplating in the upcoming weeks:

1) Should I conduct a t-test for each of the different movies and then conduct a meta-test on all of them, or should I sum their ratings first?

2) Given a large sample like the non-US ratings for Logan's Run here, how do I calculate the standard deviation? I know the formula and I can do it for small samples where I can input each value but this larger one is giving me trouble.

3) Would a sample based on only the 2000s be more indicative of current cultural trends? I think it might, because so many of the old movies have pre-existing cultural status that US or non-US raters might be especially biased before watching.

4) Is the world is a mere hotch-potch of random cohesions and dispersions, or is it a unity of order and providence? Should I care?

Sunday, January 11, 2009

Where are all the mp3 players?

Walking around in downtown SF, I am consistently surprised by how few people are listening to iPods or other mp3 players. The percentage is maybe 5-10% on a good day.

Contrast that to what percentage of people listen to the radio or CDs while they drive their cars, which is well above 50% from my personal experience. If so many people listen to the radio in the car, it doesn't make sense that so few would listen to their mp3 players while walking around outside. I have a few hypotheses to explain this discrepancy in behavior:

1) They expect to run in to somebody and begin to talk with them, and feel that it will be awkward if they have to take off their headphones in order to have this conversation.

2) People have fewer mp3 players than I expect based on my biased college student sample. CNET reported in 2006 that 20% of people owned a portable mp3 player, however, so I would expect that by now that number would be about 30%. And in an affluent city like San Francisco, this percentage of the population ought to be even higher. This is no excuse.

3) Walkers actually prefer to listen to the hustle and bustle of the city, or to hear an occasional bird chirp. Yawn.

4) Pedestrians are worried that listening to an iPod will make them more likely to be hit by a car or otherwise put in danger (by a construction site, for example).

5) Social pressure portrays listening to an mp3 player as a negative activity. People conform to societies expectations and deny themselves the pleasure of listening to music.

Numbers 1-4 strike me as woefully inadequate, and therefore I am forced to put forth number 5 as the primary explanation. It is a sad state of affairs for modern society that people deny themselves the pleasure of music, especially since we generally rate commuting to be our least favorite activity, and music or a podcost could help mitigate our boredom. This is why, by the way, I didn't particularly like Wall-E.

The next time that you feel bad about putting your mp3 player and entering your own world in a public place, picture me giving you a big thumbs up. Love yourself for what you are, not for what society wants you to be.

Thursday, January 8, 2009

Why is expected value poker less fun?

Modern statistical techniques allow you to rapidly compute the odds that a particular hand will win a given show down at very high accuracy. There are tons of website that will do this for free; this website is merely the first result on Google.

Expected value poker would be a variant of the normal game that takes advantage of this capability. The main change from the normal game is that anytime there is a show down between two players the pot would be split based on the odds each player currently has to win the hand.

For example, if one player had AK suited and the other had 22 of different suits before the flop the pot would be split almost evenly, because the odds are 49.7% versus 49.6%. In the normal game, these odds are played out and one player takes the whole pot while the other is left with nothing.

Just like my plan to reformat multiple choice tests, this new game variant would reduce variation due simply to luck and thus would be more fair. Unlike my other proposal, this one strikes me as possibly less fun than the normal game. So, two questions: 1) Do you believe that this game variant would be less fun?, and 2) Why?.

Addendum: Nick Kisberg sends along a link explaining what expected value poker is.

Tuesday, January 6, 2009

How will the digitization of old journals affect opinions toward science?

In a recent correspondence to Nature, William Burns predicts the effects of digitizing old scientific journals:
... We can now also search deep into the past. And what turns up isn't necessarily pretty... One of [Soviet geneticist Trofim Denisovich Lysenko]'s reports, in a 1947 issue of the journal Literaturnaya Gazeta, declaimed that: "intraspecific competition does not occur... the opposition of bourgeois geneticists to this theory is attributed to their desire to justify capitalist exploitation, which is essentially a struggle within the human species".

Another search, using Web of Knowledge, brought up hundreds of Chinese scientific articles from the decades after Mao Zedong came to power in 1949, with titles such as 'Chairman Mao's brilliant philosophic thought guides me in winning triple cropping with high yield'....

But will this censorship be possible when every politically motivated, unethical and demonstrably incorrect scientific article breaks out from dusty library storerooms to appear online? How will anyone be able to believe that science is an honest quest for truth, when its inglorious past is a mouse click away?
I have three immediate reactions:

1) Burns casts this development in a somewhat negative light, but I think it would be undoubtedly be positive. There have been too many dystopian novels written by 2009 for any serious thinker to doubt the importance of being skeptical of authority.

2) I question whether this so-called wealth of available knowledge will actually change many people's searching habits. If celebrated columnists like David Brooks cannot even open a scientific journal, why should we expect that the average internet user will?

3) Those are two awesome examples of how politics can invade and infect the realm of science.

Monday, January 5, 2009

Comparative studies on brain health supplements needed

This article does a pretty good job of listing all of the various diets that are "good" for your brain and explaining why each of them work. Here are all of the particulars mentioned: boosting vitamin and mineral intake, increasing the time interval between meals, rosemary herb, alpha-lipoic acid, acetyl-L-carnitine, omega-3's EPA and DHA, calorie restriction, intermittent fasting, turmeric (which contains curcumin), physical exercise (especially if it's fun), meditation, lifestyle changes to reduce stress, and generally anti-oxidant rich foods.

That is just one article (what about blueberries?), and that is just for the brain. But what if you want to have a healthy heart, or a healthy liver? Well there's also a bunch of stuff you need to eat for that.

I'm sick of hearing what's good. I have a limited amount of time, a limited amount of money, and a limited amount of mental effort I'm willing to spend planning my diet. From now on, I want to hear about what is best.

Saturday, January 3, 2009

Why imdb matters -- our time is scarce

There are perhaps an infinite number of possible criticisms of imdb espoused in everyday conversation. I'll address more of these in future posts, but first, the most common criticism: Why is imdb necessary at all?

If you google "how many films have ever been made?" you get a few search results, like this wiki answers, of people asking the question. But of course nobody knows the answer for sure. That's because there have been a *&#-load of movies made in the last 100 years, and there is no way that any one man or woman could watch every one of them.

So, you need a way to filter out the trashy movies before you waste 90 minutes of you life. Like that time you watched "Surf Ninjas of the South China Sea"… or were you trying to forget about that?

It's true that you could rely on the opinion of experts like Enert and Doper. But many of these soulless men spend their days locked in ivory towers obsessing over what angle their thumb should be oriented in. What makes you think that your tastes will be the same as theirs?

Instead, your best option is to harness the wisdom of the crowds and watch movies based on imdb's ratings. Yes there are biases in these ratings, and I'll address some of them in future posts. But overall there is no system that can match imdb's massive amount of opinions, and it is this critical mass that cancels out many of the biases that affect individuals.

And what about respecting the artists? As cinemaphile Tyler Cowen explains in Discover Your Inner Economist,
We must ignore the carping of the sophisticates. Well-educated critics may claim that pictures cannot be ranked, value is multidimensional or subjective, or that such talk represent a totalizing, colonizing, possessive, postcapitalist, hegemonic Western imperalist approach. All of those missives are beside the point. When it comes to the arts, dealing with the scarcity of our attention is more important than anything, including respecting the artists.
It may sound harsh to not watch a movie simply because it only received an average rating of 6.4 out of 10. But our time is scarce, and we live in an unfair world. We must either adapt to the evolving landscapes or be crushed under the unforgiving winds of change. Respect yourselves, and Godspeed.