Surprising Results from Game Theory Studies

If you're trying to outwit the competition, it might be better to have been born a chimpanzee, according to a study by researchers at Caltech, which found that chimps at the Kyoto University Primate Research Institute consistently outperform humans in simple contests drawn from game theory.

The study, led by Colin Camerer, Robert Kirby Professor of Behavioral Economics, and appearing on June 5 in the online publication Scientific Reports, involved a simple game of hide-and-seek that researchers call the Inspection Game. In the game, two players (either a pair of chimps or a pair of humans) are set up back to back, each facing a computer screen. To start the game, each player pushes a circle on the monitor and then selects one of two blue boxes on the left or right side of the screen. After both players have chosen left or right, the computer shows each player her opponent's choice. This continues through 200 iterations per game. The goal of the players in the "hiding" role—the "mismatchers"—is to choose the opposite of their opponent's selection. Players in the "seeking" role—the "matchers"—win if they make the same choices as their opponent. Winning players receive a reward: a chunk of apple for the chimps or a small coin for the humans. If players are to win repeatedly, they have to accurately predict what their opponent will do next, anticipating their strategy.

The game, though simple, replicates a situation that is common in the everyday lives of both chimps and humans. Study coauthor Peter Bossaerts, a visiting associate in finance at Caltech, gives an example from human life: an employee who wants to work only when her employer is watching and prefers to play video games when unobserved. To better conceal her secret video game obsession, the employee must learn the patterns of the employer's behavior—when they might or might not be around to check up on the worker. Employers who suspect their employees are up to no good, however, need to be unpredictable, popping in randomly to see what the staff is doing on company time.

The Inspection Game not only models such situations, it also provides methods to quantify behavioral choices. "The nice thing about the game theory used in this study is that it allows you to boil down all of these situations to their strategic essence," explains Caltech graduate student and coauthor Rahul Bhui.

However cleverly you play the Inspection Game, if your opponent is also playing strategically, there is a limit to how often you can win. That limit, many game theorists agree, is best described by the Nash equilibrium, named for mathematician John Forbes Nash Jr., winner of the 1994 Nobel Memorial Prize in Economic Sciences, whose life and career provided the inspiration for the Academy Award–winning 2001 film A Beautiful Mind.

In the first part of this study, coauthors Chris Martin and Tetsuro Matsuzawa compared the game play of six common chimpanzees (Pan troglodytes) and 16 Japanese students, always facing off against their own species, in the Kyoto research facility. The humans behaved as expected based on previous experiments; that is, they played reasonably well, slowly learning to predict opponent choices, but they did not play optimally. They ended up somewhat off the Nash equilibrium.

The performance of the chimps was far more impressive: they learned the game rapidly and nearly attained the predictions of the Nash theorem for optimal play. They continued to do so even as researchers introduced changes into the game, first by having players switch roles—matchers (seekers) becoming mismatchers (hiders), and vice versa—and then by adjusting the payoffs such that matchers received greater rewards when matching on one side of the screen (left or right) rather than the other. This latter adjustment changes the Nash equilibrium for the game, and the chimps changed right along with it.

In a second phase of the experiment in Bossou, Guinea, 12 adult men were asked to face one another in pairs. Instead of touching dots on a computer screen on the left or right, the men in Bossou each had a bottle cap that they placed top up or top down. As in the Kyoto experiments, one player in each pair was a mismatcher (hider) and the other was a matcher (seeker). However, the stakes were much higher in Bossou, amounting to about one full day's earnings for the winner, as opposed to the rewards for the Japanese students, who received a handful of one yen coins. Still, the players in Bossou did not match chimpanzee performance, landing as far off the Nash equilibrium as the Japanese students did.

A couple of simple explanations could account for the ability of these chimpanzees to outperform humans in the game. First, these particular chimps had more extensive training at this kind of task as well as more experience with the equipment used at the Research Institute than the human subjects did. Second, the chimps in Kyoto were related to one another—they played in mother-child pairs—and thus may have had intimate knowledge, borne of long acquaintance, of the sequence of choices their opponents would probably make.

Neither explanation seems likely, researchers say. Although the Japanese students may not have had experience with the type of touch screens employed in the Kyoto facility, they certainly had encountered video games and touch screens prior to the experiment. Meanwhile, the players in Bossou knew each other very well prior to the experiments and had the additional advantage of seeing one another while they played, yet they performed no better than the Japanese students.

Superior chimpanzee performance could be due to excellent short-term memory, a particular strength in chimps. This has been shown in other experiments undertaken at the Kyoto facility. In one game, a sequence of numbers is briefly flashed on the computer touch screen, and then the numbers quickly revert to white squares. Players must tap the squares in the sequence corresponding to the numbers they were initially shown. Chimpanzees are brilliant at this task, as video from the experiment shows; humans find it much more challenging, as seen in video from the Primate Research Center.

But before we join a species-specific pity party over our inferior brains, rest assured that researchers offer other explanations for chimpanzee superiority at the Inspection Game. There are two possible explanations that researchers currently find plausible. The first has to do with the roles of competition and cooperation in chimpanzee versus human societies; the second with the differential evolution of human and chimpanzee brains since our evolutionary paths split between 4 and 5 million years ago.

The past half-century has seen an enormous divergence of opinion as to how cooperative or competitive humans "naturally" are, and though this debate is far from settled, it is clear that wherever humans sit on the cooperative/competitive scale, common chimpanzees are more competitive with one another than we are. They create and continuously update a strong status and dominance hierarchy. (Another type of chimpanzee, Pan paniscus, or the bonobo, is considerably more cooperative than Pan troglodytes, but the former has not been studied as extensively as the latter.) Humans, in contrast, are highly prosocial and cooperative. Camerer notes that this difference is apparent in chimp and human social development. "While young chimpanzees hone their competitive skills with constant practice, playing hide-and-seek and wrestling, " says Camerer, "their human counterparts shift at a young age from competition to cooperation using our special skill at language."

Language is probably a key factor here. In the Inspection Game experiments, humans were not allowed to speak with one another, despite language being "key to human strategic interaction," according to Martin.

Language is also implicated in the "cognitive tradeoff hypothesis," the second explanation for the chimps' superior performance in the Inspection Game. According to this hypothesis, developed by Matsuzawa, the brain growth and specialization that led to distinctly human cognitive capacities such as language and categorization also caused us to process certain simpler competitive situations—like the Inspection Game—more abstractly and less automatically than our chimpanzee cousins.

These explanations remain speculative, but eventually, Bhui predicts, new technologies will make it possible to "map out the set of brain circuits that humans and chimps rely upon so we can discover whether or not human strategic choices go down a longer pathway or get diffused into different parts of the brain compared to chimps."

Funding for this experiment, described in a paper entitled "Chimpanzee choice rates in competitive games match equilibrium predictions," was provided by the Ministry of Education, Culture, Sports, Science and Technology in Japan; the Gordon and Betty Moore Foundation; the Social Sciences and Humanities Research Council of Canada; and Caltech's Division of the Humanities and Social Sciences.

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Cynthia Eller
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Tuesday, July 22, 2014
Center for Student Services 360 (Workshop Space)

Teaching Quantum Mechanics with Minecraft and Comics

Ditch Day? It’s Today, Frosh!

Today we celebrate Ditch Day, one of Caltech's oldest traditions. During this annual spring rite—the timing of which is kept secret until the last minute—seniors ditch their classes and vanish from campus. Before they go, however, they leave behind complex, carefully planned out puzzles and challenges—known as "stacks"—designed to occupy the underclass students and prevent them from wreaking havoc on the seniors' unoccupied rooms.

Follow the action on Caltech's Facebook and Twitter pages as the undergraduates tackle the puzzles left around campus for them to solve, and get in on the conversation by sharing your favorite Ditch Day memories. Be sure to use #CaltechDitchDay in your tweets and postings.

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In Our Community
Thursday, September 25, 2014
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2014 Caltech Teaching Conference

Tuesday, May 13, 2014
Avery Library

Semana Latina Keynote Speaker – Dr. Rodolfo Mendoza-Denton

Friday, May 16, 2014
Center for Student Services 360 (Workshop Space)

The Role of Writing in Building a Research Career

Friday, May 30, 2014
Annenberg 105

Caltech Teaching Assistant Training for 2014-2015 Year

Research Update: An Autism Connection

Caltech neuroscientists find link between agenesis of the corpus callosum and autism

Building on their prior work (see "Bridging the Gap"), a team of neuroscientists at Caltech now report that rare patients who are missing connections between the left and right sides of their brain—a condition known as agenesis of the corpus callosum (AgCC)—show a strikingly high incidence of autism. The study is the first to show a link between the two disorders.

The findings are reported in a paper published April 22, 2014, in the journal Brain.

The corpus callosum is the largest connection in the human brain, connecting the left and right brain hemispheres via about 200 million fibers. In very rare cases it is surgically cut to treat epilepsy—causing the famous "split-brain" syndrome, for whose discovery the late Caltech professor Roger Sperry received the Nobel Prize. People with AgCC are like split-brain patients in that they are missing their corpus callosum—except they are born this way. In spite of this significant brain malformation, many of these individuals are relatively high-functioning individuals, with jobs and families, but they tend to have difficulty interacting with other people, among other symptoms such as memory deficits and developmental delays. These difficulties in social behavior bear a strong resemblance to those faced by high-functioning people with autism spectrum disorder.

"We and others had noted this resemblance between AgCC and autism before," explains Lynn Paul, lead author of the study and a lecturer in psychology at Caltech. But no one had directly compared the two groups of patients. This was a challenge that the Caltech team was uniquely positioned to do, she says, since it had studied patients from both groups over the years and had tested them on the same tasks.

"When we made detailed comparisons, we found that about a third of people with AgCC would meet diagnostic criteria for an autism spectrum disorder in terms of their current symptoms," says Paul, who was the founding president of the National Organization for Disorders of the Corpus Callosum.

The research was done in the laboratory of Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology at Caltech and a coauthor of the study. The team looked at a range of different tasks performed by both sets of patients. Some of the exercises that involved certain social behaviors were videotaped and analyzed by the researchers to assess for autism. The team also gave the individuals questionnaires to fill out that measured factors like intelligence and social functioning.

"Comparing different clinical groups on exactly the same tasks within the same lab is very rare, and it took us about a decade to accrue all of the data," Adolphs notes.

One important difference between the two sets of patients did emerge in the comparison. People with autism spectrum disorder showed autism-like behaviors in infancy and early childhood, but the same type of behaviors did not seem to emerge in individuals with AgCC until later in childhood or the teen years.

"Around ages 9 through 12, a normally formed corpus callosum goes through a developmental 'growth spurt' which contributes to rapid advances in social skills and abstract thinking during those years," notes Paul. "Because they don't have a corpus callosum, teens with AgCC become more socially awkward at the age when social skills are most important."

According to Adolphs, it is important to note that AgCC can now be diagnosed before a baby is born, using high-resolution ultrasound imaging during pregnancy. This latest development also opens the door for some exciting future directions in research.

"If we can identify people with AgCC already before birth, we should be in a much better position to provide interventions like social skills training before problems arise," Paul points out. "And of course from a research perspective it would be tremendously valuable to begin studying such individuals early in life, since we still know so little both about autism and about AgCC."

For example, the team would like to discern at what age subtle difficulties first appear in AgCC individuals, and at what point they start looking similar to autism, as well as what happens in the brain during these changes.

"If we could follow a baby with AgCC as it grows up, and visualize its brain with MRI each year, we would gain such a wealth of knowledge," Adolphs says.

The Brain paper, "Agenesis of the Corpus Callosum and Autism: A Comprehensive Comparison," also includes as coauthors Daniel Kennedy, assistant professor of psychology at Indiana University, and Christina Corsello, a member of the research staff at Rady Children's HospitalSan Diego. The research was funded by the Simons Foundation, Autism Speaks, and the Brain and Behavior Research Foundation.

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On the Front Lines of Sustainability

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On the Front Lines of Sustainability
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The chemical processes used to make products ranging from pharmaceuticals to perfumes can have a harmful impact on the environment. However, Caltech chemist and Nobel laureate Robert Grubbs has spent several decades developing catalysts—compounds that speed up a chemical reaction—that can make the synthesis of these products more efficient and ecologically friendly, ultimately reducing their environmental footprint. Similarly, chemist Brian Stoltz is developing new strategies for the synthesis of compounds needed in the chemical, polymer, and pharmaceutical industries. His new processes rely upon oxygen and organometallic catalysts—greener alternatives to the toxic metals that are normally used to drive such reactions.

Switching from paper files to cloud-based data storage might seem like an obvious choice for sustainability, but can we further reduce the environmental impact of storing data? The theoretical work of engineer and computer scientist Adam Wierman suggests that with the right algorithms, we can. Today, data centers—the physical storage facilities Wierman calls the "SUVs of the Internet"—account for more than 1.5 percent of U.S. electricity usage. And as more data goes online, that number is expected to grow. Wierman's work helps engineers design algorithms that will reroute data, with preference to centers that use renewable energy sources like wind and solar.

Energy from the sun—although free and abundant—cannot easily be stored for use on dreary days or transported to cloudy regions. Caltech engineer and materials scientist Sossina Haile hopes to remove that barrier with a specific type of solar reactor she has developed. The reactor is lined with ceramic cerium oxide; when this lining is heated with concentrated sunlight it releases oxygen, priming it to remove oxygen from water molecules or carbon dioxide on cooling, thus creating hydrogen fuel or "syngas"—a precursor to liquid hydrocarbon fuels. This conversion of the sun's light into storable fuel could allow solar-derived power to be available day and night.

Caltech student participants in the Department of Energy's biennial Solar Decathlon competition set out to prove that keeping a house lit up, cooled down, and comfortable for living is possible—even while off the grid. The Techers teamed up with students at the Southern California Institute of Architecture to create CHIP and DALE, their entries in the 2011 and 2013 competitions, respectively. These functional and stylish homes, powered solely by the sun, were engineered with innovative components including a rainwater collection system and moving room modules that optimize heating and cooling efficiency. 

Although many of us take the nearest bathroom for granted, working toilets require resources and infrastructure that may not be available in many parts of the world. Inspired by the "Reinventing the Toilet Challenge" issued by the Bill and Melinda Gates Foundation, environmental scientist and engineer Michael Hoffmann and his team applied his research in hydrogen evolution and water treatment to reengineer the toilet. The Caltech team's design—which won the challenge in 2012—can serve hundreds of people each day, treat its own wastewater, and generate electricity, providing a sustainable and low-cost solution to sanitation and hygiene challenges in the developing world. Prototypes are being tested in India and China for use in urban and remote environments in the developing world.  

Geophysicist Mark Simons studies the mechanics of the Earth—furthering our understanding of what causes our planet to deform over time. His research often involves using satellite data to observe the movement associated with seismic and volcanic activity, but Simons is also interested in changes going on in the icy parts of Earth's surface, especially the dynamics of glaciers. By flying high above Iceland's ice caps, Simons and his colleagues can track the glaciers' melt-and-freeze response in relation to seasonal and long-term variations in temperature—and their potential response to climate change.

The production of industrial nitrogen fertilizer results in 130 million tons of ammonia annually—while also requiring high heat, high pressure, and lots of energy. However, in a process called nitrogen fixation, soil microorganisms that live near the roots of certain plants can produce a similar amount of ammonia each year. The bugs use catalysts called nitrogenases to convert nitrogen from the air into ammonia at room temperature and atmospheric pressure. By mimicking the behavior of these microorganisms, Jonas Peters and his colleagues synthesized an iron-based catalyst that allows for nitrogen fixation under much milder conditions. The catalyst could one day lead to more environmentally friendly methods of ammonia production.

Traditionally, the photovoltaic cells in solar panels have been expensive and have had limited efficiency—making them a hard sell in the consumer market. Engineer and applied physicist Harry Atwater's work suggests that there is a thinner and more efficient alternative. Atwater, who is also the director of the Resnick Sustainability Institute, uses thin layers of semiconductors to create photovoltaics that absorb sunlight as efficiently as thick solar cells but can be produced with higher efficiency than conventional cells.

The generation of chemical fuels from sunlight could completely change the way we power the planet. Researchers in the laboratory of Caltech chemist Nate Lewis are working to develop different components of a fuel-producing device that could do just that called a photoelectrochemical cell. The cell would consist of an upper layer that could absorb sunlight, carbon dioxide, and water vapor, a middle layer consisting of light absorbers and catalysts that can produce fuels, which are then released through the device's bottom layer. When such a device is created, the Joint Center for Artificial Photosynthesis, of which Lewis is the scientific director, aims to ease the transfer of these technologies to the private sector. 

Clean energy from the wind is a promising alternative to fossil fuels, but giant pinwheel-like wind turbines that are common on many wind farms can create dangerous obstacles for birds as well as being an unpleasant addition to a landscape's aesthetic. To combat this problem, Caltech engineer and fluid-mechanics expert John Dabiri is testing a new design for wind turbines, which looks a bit like a spinning eggbeater emerging from the ground. By placing these columnar vertical wind turbines in a careful arrangement—an arrangement inspired by the vortex of water created behind a swimming fish—his smaller vertical turbines create just as much energy as the "pinwheels" and on a much smaller land footprint.

In the early 1990s, Caltech bioengineer Frances Arnold pioneered "directed evolution"—a new method of engineering custom-built enzymes, or activity-boosting proteins. The technique allows mutations to develop in the enzyme's genetic code; these mutations can give the enzyme properties that don't occur in nature but are beneficial for human applications. The selectively enhanced enzymes help microbes turn plant waste and fast-growing grasses into fuels like isobutanol, which could sustainably replace more than half of U.S. oil imports, Arnold says. She's also exploring ways the technique could help factories to make pharmaceuticals and other products in much cleaner and safer ways.

The combined research efforts of Richard Flagan, John Seinfeld, Mitchio Okumura, and Paul Wennberg aim to improve our understanding of various aspects of climate change. Chemical engineer Flagan is pioneering ways to measure the number and sizes of particles in the air down to that of large molecules. Seinfeld studies where particles in the air come from, how they are produced by airborne chemical reactions, and the effect they have on the world's climate. Chemical physicist Okumura studies the chemical reactions that occur when sunlight encounters air pollution and results in smog. Wennberg, an atmospheric chemist, studies the natural and human processes that affect smog formation, the health of the ozone layer, as well as the lifetime of greenhouse gases. Wennberg and his colleagues join a legacy of Caltech researchers who have improved air quality through key discoveries about pollution.

In the past, researchers have discovered materials that can act as reaction catalysts, driving sunlight to split water into hydrogen fuel and an oxygen byproduct. However, these wonder materials are often expensive and in short supply. The research of chemist Harry Gray, who leads the National Science Foundation-funded Center for Chemical Innovation in Solar Fuels program, tests combinations of Earth-abundant metals to search for an inexpensive catalyst that boosts the water-splitting reaction with the sun. Gray also coleads an outreach project in which students in the classroom can participate in the race for solar fuels by testing thousands of materials and reporting their results to Caltech researchers.

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Although Earth Week has officially come to a close, Caltech's commitment to sustainability continues. In this feature, you will meet some of the researchers at Caltech whose work is contributing to a greener planet and to the long-term improvement of our global environment.

Monday, May 5, 2014
Center for Student Services 360 (Workshop Space)

Experiences from two years of MOOCs at Caltech: A WEST Public Seminar

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