This is Your Brain on Hunger

hungerIn his book Thinking Fast and SlowDaniel Kahneman describes the brain as made up of two systems. System 1 is fast, emotional, and almost automatic–I think of this as “intuition.” System 2 controls more logical, deliberate processes. There are many factors that can influence which system you use to make a decision (anchoring, availability, substitution, loss aversion, framing, etc.) and Kahneman’s book discusses these. But other environmental factors can influence which system takes over. This post discusses how hunger shifts the balance from System 2 to System 1.

First up is a study on Israeli judges’ parole decisions broken up by time of day by Shai DanzigeraJonathan Levavb, and Liora Avnaim-Pessoa (edited for PNAS  by Kahneman). Here’s the abstract:

Are judicial rulings based solely on laws and facts? Legal formalism holds that judges apply legal reasons to the facts of a case in a rational, mechanical, and deliberative manner. In contrast, legal realists argue that the rational application of legal reasons does not sufficiently explain the decisions of judges and that psychological, political, and social factors influence judicial rulings. We test the common caricature of realism that justice is “what the judge ate for breakfast” in sequential parole decisions made by experienced judges. We record the judges’ two daily food breaks, which result in segmenting the deliberations of the day into three distinct “decision sessions.” We find that the percentage of favorable rulings drops gradually from ≈65% to nearly zero within each decision session and returns abruptly to ≈65% after a break. Our findings suggest that judicial rulings can be swayed by extraneous variables that should have no bearing on legal decisions.

The Economist summarized the paper and produced a graphic with the main takeaway:


The second paper, by Ilona Grunwald-Kadow and coauthors, analyzes the neural behavior of fruit flies when deprived of food (via @tylercowen and @IFLscience). Their results are explained in this press release from the Max Planck Institute:

The results show that the innate flight response to carbon dioxide in fruit flies is controlled by two parallel neural circuits, depending on how satiated the animals are. “If the fly is hungry, it will no longer rely on the ‘direct line’ but will use brain centres to gauge internal and external signals and reach a balanced decision,” explains Grunwald-Kadow. “It is fascinating to see the extent to which metabolic processes and hunger affect the processing systems in the brain,” she adds.

Remember this next time you’re trying to decide between working through lunch or grabbing a bite to eat. Do your body and your neighbors a favor by taking a break.

See also: 

Currency and Conflict

According to Lebanon’s Daily Star:

Traders across Syria reported widely fluctuating rates and two currency dealers in Damascus, where the pound appeared to be hit hardest, said it fell below 200 to the dollar for the first time in what one described as panic buying of the U.S. currency.

On Monday evening the pound traded at 205 to the dollar, down 20 percent in four days and 77 percent down since the start of the anti-Assad uprising in March 2011 when it was at 47.

The idea of examining currency prices over the course of a conflict is interesting. There are a number of confounders of course. For instance, the regime can often intervene in certain ways to affect the value of currency. Other incidents besides the conflict itself can also drive currency fluctuations, especially when the conflict is relatively minor.

One nice case (from strictly a research perspective) is the US Civil War, when both the Union and Confederacy issued their own notes. Jeffrey Arnold‘s project, “Pricing the Costly Lottery: Financial Market Reactions to Battlefield Events in the American Civil War,” leverages this fact to see how markets responded to successes and failures of either side. We discussed this project before when it was presented as a poster at PolMeth 2012, and Jeffrey’s website now has his MPSA 2013 slides.

Here’s his abstract, and one of my favorite graphs:

What role does combat play in resolving the disagreement that initiated war? Bargaining theories of war propose two mechanisms, the destruction of capabilities and the revelation of private information. These mechanisms are difficult to analyze quantitatively because the mechanisms are observationally equivalent, the participants’ expectations are unobservable, and there is a lack of data on battles. With new methods and new data on the American Civil War, I address these challenges. I estimate the information revealed by combat with a model of Bayesian learning. I use prices of Union and Cnnnonfederate currencies to measure public expectations of war duration and outcome. Data on battlefield events come from detailed data on the outcomes and casualties of the battles of the American Civil War. The results suggest that battle outcomes rather than casualties or information revelation had the largest influence on the expected duration of the American Civil War.


Trade Secrets of Methodologists: A Bibliography

sciencemethWe all know what the scientific method looks like in idealized form. But the first dirty secret is that you don’t actually write a paper that way. In fact, many papers are written almost in reverse, starting with the findings and working backward. Over the weekend @Worse_Reviewer shared some papers that help to convey these secrets and make grad students aware of the tacit knowledge already put to good use by their more senior colleagues. I have obtained ungated links to the papers (or similar versions) wherever available, along with two additional articles via Mike Ward.

Recommended Packages for R 3.x

sandwichWith the recent release of R 3.0 (OS X) and 3.1 (Windows), I found myself in need of a whole host of packages for data analysis. Rather than discover each one I needed in the middle of doing real work, I thought it would be helpful to have a script with a list of essentials to speed up the process. This became even more essential when I also had to install R on a couple of machines in our department’s new offices.

Thankfully my colleague Shahryar Minhas had a similar idea and had already started a script, which I adapted and share here with his permission. The script is also on Github so if you have additions that you find essential on a new R install feel free to recommend them.

PACKAGES = c("Amelia",
install.packages('tikzDevice', repos='')

Mapping Literal Place Names

Place names are another one of those micro-institutions. They often carry a linguistic legacy indicating some important discoverer, inhabitant, or conqueror. Changes in place names are significant too. (Would Sinatra’s “New Amsterdam, New Amsterdam” have rolled off the tongue nearly as nicely?) As the names accumulate history and new generations become accustomed to them, however, we often lose the literal sense of their meaning. In an effort to help undo that, the Atlas of True Names “reveals the etymological roots, or original meanings,of the familiar terms on today’s maps of the World, Europe, the British Isles and the United States.”

Here are a couple of examples, and there is much more at the link:




facelift-lucille-arrested-developmentAs regular readers will have noticed by now, the site got a facelift about a week ago. This was much needed as the old theme had become outdated (literally–it was named “Twenty-Ten”). Some of the formatting of old posts might have been thrown off by the change. Overall, I hope you will find it a pleasant upgrade.

One thing that didn’t fly well early on was the light font I had chosen for the text in posts–in some browsers it rendered as very low-contrast. I changed it a couple of days later and hopefully it’s better now. Thanks to Daniel for commenting about this via email.

Another upcoming change is that I will be less rigorous about the Monday-Wednesday-Friday schedule of posts. Posts will likely be published at those times when they are available, but I will not make a point of posting on all three of those days every week.

The third and final change is that comments will automatically close after seven days. This is mainly because comments after that time are typically spam. If you have a response to a post more than a week after the fact, you are more than welcome to contact me on email or Twitter. And feedback about any of these changes is welcome!

Project Design as Reproducibility Aid

From the Political Science Replication blog:

When reproducing pubished work, I’m often annoyed that methods and models are not described in detail. Even if it’s my own project, I sometimes struggle to reconstruct everything after I took a longer break from a project. An article by post-docs Rich FitzJohn and Daniel Falster shows how to set up a project structure that makes your work reproducible.

To get that “mix” into a reproducible format, post-docs Rich FitzJohn and Daniel Falster from Macquarie University in Australia suggest to use the same template for all projects. Their goal is to ensure integrity of their data, portability of the project, and to make it easier to reproduce your own work later. This can work in R, but in any other software as well.

Here’s their gist. My post from late last year suggests a similar structure. PSR and I were both informed about ProjectTemplate based on these posts–check it out here.

Micro-Institutions Everywhere: Defining Death

From the BBC:

In the majority of cases in hospitals, people are pronounced dead only after doctors have examined their heart, lungs and responsiveness, determining there are no longer any heart and breath sounds and no obvious reaction to the outside world….

Many institutions in the US and Australia have adopted two minutes as the minimum observation period, while the UK and Canada recommend five minutes. Germany currently has no guidelines and Italy proposes that physicians wait 20 minutes before declaring death, particularly when organ donation is being considered….

But the criteria used to establish brain death have slight variations across the globe.

In Canada, for example, one doctor is needed to diagnose brain death; in the UK, two doctors are recommended; and in Spain three doctors are required. The number of neurological tests that have to be performed vary too, as does the time the body is observed before death is declared.

George Box, the Accidental Statistician

GeorgeEPBoxGeorge Box, renowned statistician, passed away on April 10 of this year at the age of 93. As the title of his recently released memoir suggests, he stumbled into the career that made him famous. During the Second World War, he was assigned to the Chemical Defence Experimental Station, located at Porten Down. From there, as he recounts,

[M]y job was to make biochemical determinations in experiments on small animals. The results I was getting were very variable, and I told Cullumbine that what we needed was a statistician to analyze our data. He said, “Yes, but we can’t get one. What do you know about it?” I told him I had once tried to read a book about it by someone called R.A. Fisher, but I hadn’t understood it. He said, “Well you read the book so you’d better do it.” So I said, “Yes Sir.” (Kindle Locations 750-754).

I found this book useful because so many biographies are written as if the protagonist had his or her life all planned out from the beginning. Autobiographies are a bit more honest on this front, but none as much as Box’s.

This is particularly helpful for grad students, who tend to get advice from a very biased sample: successful academics. From their accounts we can estimate the probability that someone successful took a certain course of action. But without information on those who do not become academics, it’s impossible to obtain the probability of success when adopting that same strategy. Box’s memoir alone can’t entirely undo this, of course, but he does relate stories of many of his grad students who chose positions in industry.

Here are some quotations from it that I enjoyed:

  • “A serious mistake has been made in classifying statistics as part of the mathematical sciences. Rather it should be regarded as a catalyst to scientific method itself.” (Kindle Locations 545-546).
  • “I forget whom I lied to (I expect it was the Army— they were used to it), but I did get my discharge.” (Kindle Locations 930-931).
  • “Likelihood methods are like a very intelligent but nondiscriminating child.” (Kindle Location 2024).
  • “None of this is a hanging matter.” (Kindle Location 2029).
  • “Originality and wit are very close.” (Kindle Location 2340).

The main weakness of the book is its meandering style. Box often goes from anecdote to anecdote in a train of thought style where the logic of transition is unclear to the reader. This becomes less irritating by the second half of the book, either because it received better editing or because I grew used to the style.

Overall, I recommend the book to several audiences: grad students in any quantitative field, practicing statisticians, and those who would like to know more about the personal life of this influential figure.