Caltech Researchers Reveal the Neuronal Computations Governing Strategic Social Interactions in the Human Brain

PASADENA, Calif.-- In a strategic game, the success of any player depends not just on his or her own actions, but on the behavior of every other player in the game. To be successful, players must not only pay attention to what other players do, but also how they are thinking.

Understanding how the brain functions during this strategizing is at "the core of studies of adaptive social intelligence," says John P. O'Doherty of the California Institute of Technology and the subject of a recent series of brain studies by O'Doherty and his colleagues that offer new insight into how the brain works in social situations.

O'Doherty, an associate professor of psychology, along with graduate student Alan N. Hampton and Peter Bossaerts, William D. Hacker Professor of Economics and Management and professor of finance at Caltech, had volunteers participate in a simple two-player strategy game. In the game, volunteers were assigned to play either the role of an employer or an employee, and were isolated from one another. One of them was placed within a functional MRI machine, which measured brain activity in real time.

During each trial, the participant acting as the employee had to choose to either work or not work, and the employer had to decide to check up on his employees ("inspect"), or to leave them alone ("not inspect"). What each party selects will depend both on their own goals and on their anticipation of the behavior of the other participant. For example, the employer, who is busy with other work, does not want to waste time checking on his employees, but does want to occasionally inspect them to make sure they're not slacking off--and to let them know he's watching. His employees, however, prefer to shirk their duties as much as possible when not being inspected, but would rather be found working when the employer decides to check on them.

To provide real incentive for the volunteers, they were given a small monetary award based on the outcome of each trial. An employer's maximum payoff, $1.00, occurs when his employees are working, and he does not check on them; employees in this situation earn nothing. An employer's worst payoff--$0.00--is assigned either when his employees are working and his mistrust leads him to inspect anyway, or when his employees are shirking and he does not inspect; in both scenarios, the employees earn $.50. In the final case, employees who are caught shirking get nothing, while their boss gets $.25.

The game is set up such that there is no possibility of a tie, with an equal payoff for both players. "It's a competitive situation," O'Doherty explains, "so each person has to keep anticipating and predicting the behavior of the other person, to outguess them"--and maximize their own profit.

"The whole point of this game is the idea that in order to do well, you have to predict what the other player is going to do, and for that you need to know what the other player thinks you are going to do," says O'Doherty.

This type of thought, in which a person creates a mental representation of the thoughts of another person, is known as mentalizing. "We're trying to understand the rules that the brain uses to make these representations. How do I take my perception of what you've done and then use that to work out what to do next? How does the brain transform information and then produce behavior?" O'Doherty says.

O'Doherty and his colleagues used a simple mathematical model that can solve such a game by taking into account the history of the opponent's choices to work out what that opponent is likely to do next. They found that subjects' actual choices could be predicted well by such a model. Furthermore, a number of brain areas previously implicated in mentalizing, such as the superior temporal sulcus (STS) and medial prefrontal cortex (mPFC), showed changes in their activity over time. These changes are predicted by the mathematical model, suggesting that the brain itself uses mathematical operations similar to that encapsulated in the model to solve the task.

O'Doherty and his colleagues found that activity in the mPFC changed depending on the subjects' success in past trials, while activity in STS reflected how that success compared with how well they thought they'd do. Furthermore, activity in the two brain areas appeared to be linked. "If the subjects were surprised by their prediction success"--if, say, they did more poorly than they had expected--"we saw increased activity in the STS. At the same time, there was increased correlation between activity in the STS and the mPFC," O'Doherty says.

This suggests, he says, that "the STS modulates the activity of the mPFC, telling it to refine its expectations, which can ultimately lead to a change in the subjects' behavior."

"This research is getting at the essence of how the brain functions in social situations," he says. Such studies could, therefore, eventually shed light on disorders, such as autism, that involve problems with social interaction.

The paper, "Neural correlates of mentalizing-related computations during strategic interactions in humans," was published in the May 6 issue of the Proceedings of the National Academy of Science. The work was partially funded by the Gordon and Betty Moore Foundation.

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How Fairness Is Wired in the Brain

PASADENA, Calif.--In the biblical story in which two women bring a baby to King Solomon, both claiming to be the mother, he suggests dividing the child so that each woman can have half. Solomon's proposed solution, meant to reveal the real mother, also illustrates an issue central to economics and moral philosophy: how to distribute goods fairly.

Now, researchers at the California Institute of Technology have discovered that reason struggles with emotion to find equitable solutions, and have pinpointed the region of the brain where this takes place. The concept of fairness, they found, is processed in the insular cortex, or insula, which is also the seat of emotional reactions.

"The fact that the brain has such a robust response to unfairness suggests that sensing unfairness is a basic evolved capacity," notes Steven Quartz, an associate professor of philosophy at Caltech and author of the study, voicing a sentiment that anyone who has seen children fight over a treat can relate to.

"The movement to look into the neural basis for ethical decision making is only about seven years old," Quartz adds. "This is the first study where people made real decisions with real consequences."

The subjects in the study, 26 men and women between 28 and 55 years old, faced a real-world moral dilemma. They started their participation in the experiment by reading a short biography of each of the 60 orphans at the Canaan Children's Home in Uganda. The orphanage would receive a sum of money that would depend on decisions the subjects made. In the end, $2,279 was donated.

While a functional magnetic resonance imaging (fMRI) machine scanned their brains for peak activity regions, the participants each had about eight seconds to decide how to distribute meals among groups of children in different scenarios. In one, their choice would grant either four extra meals to each of two children or six extra meals to one child. The children they didn't choose would get nothing. In another scenario, the kids had been given extra meals and the subjects had to decide whether it was better to take six meals away from each of two kids, or ten meals away from one.

Ultimately the subjects' brains made a choice, and Quartz and his collaborators got to peek into where that calculation was made. "You wonder what is happening at different levels--is your brain's decision right or not?"

When they got to give food to the children, the study participants' orbital frontal cortex, the reward region of the brain, lit up. When instead they had to take food away, the insula region--the emotional processor--was activated.

Quartz suggests that the insula was triggered by the inequity of the choices. The activity varied considerably across subjects, indicating that individual differences in moral sensitivity may be rooted in the strength of the biological responses, he adds.

"The emotional response to unfairness pushes people from extreme inequity and drives them to be fair," Quartz says. This observation, he adds, suggests that "our basic impulse to be fair isn't a complicated thing that we learn."

This study, which appears in the May 8 early online edition of the journal Science, is the first to examine "neuroethics"--the neural underpinnings of moral decision making--with real-world consequences. It may also help guide how to make policy decisions about distributing resources. And, adds Jonathan Katz, chair of Caltech's Division of the Humanities and Social Sciences, "It's one of the first studies to bridge humanities research with social science and biology," a central effort at Caltech.

Other authors are former Caltech graduate students Ming Hsu. and Cédric Anen. Hsu is now a postdoc at the University of Illinois at Urbana-Champaign.

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Two Faculty Members Join American Academy of Arts and Sciences

PASADENA, Calif.--Caltech professors Michael Dickinson and Thomas Palfrey are among the 190 new fellows elected to the American Academy of Arts and Sciences this year. They join an assembly that was founded in 1780 by John Adams, James Bowdoin, John Hancock, and other scholars to provide practical solutions to pressing issues.

Their election brings the Caltech total membership to 86.

Thomas Palfrey, Caltech's Flintridge Foundation Professor of Economics and Political Science and also a Caltech grad (PhD '81), specializes in the study of voting and elections, economic and political theory, public and experimental economics, and game theory.

A central focus of Palfrey's research is how people devise strategies when faced with incomplete information. He has applied game theory to examine voting behavior in committees and elections, and bidding in auctions. He founded or cofounded several experimental labs, including the California Social Science Experimental Laboratory at UCLA, the Social Science Experimental Laboratory at Caltech, and the Princeton Social Science Experimental Laboratory, and used observations from experiments to help develop a general theory of strategic behavior with human error. Called Quantal Response Equilibrium, it has been successfully applied to study a broad range of political and economic behavior.

Michael Dickinson, the Zarem Professor of Bioengineering at Caltech, studies animal physiology and behavior. He has become well known for Robofly, a mechanical fly that sprang from his work on the neurobiology and biomechanics of fly locomotion. Throughout his career, Dickinson has used a variety of tools, such as wind tunnels, virtual reality simulators, high-speed video, and giant robotic models, to determine how the poppy seed-sized brains of these tiny insects can rapidly control aerodynamic forces.

More than a simple understanding of the material basis for insect flight, Dickinson's studies provide insight into complex systems operating on biological and physical principles: neuronal signaling within brains, the dynamics of unsteady fluid flow, the structural mechanics of composite materials, and the behavior of nonlinear systems are all linked when a fly takes wing.

"The Academy honors excellence by electing to membership remarkable men and women who have made preeminent contributions to their fields, and to the world," says Academy president Emilio Bizzi. "We are pleased to welcome into the Academy these new members to help advance our founders' goal of 'cherishing knowledge and shaping the future.'" An independent policy research center, the Academy currently focuses on science, technology, and global security; social policy and American institutions; the humanities and culture; and education.

Dickinson and Palfrey will be inducted into the Academy at a ceremony on October 11, at the organization's headquarters in Cambridge, Massachusetts.

Other new members include legendary blues guitarist B. B. King, two-time cabinet secretary and former White House Chief of Staff James Baker III, and former eBay CEO Margaret Whitman, as well as foreign honorary member Pedro Almodóvar, a Spanish film director. 

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Elisabeth Nadin
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Locating a "Free Choice" Brain Circuit

PASADENA, Calif.--Your brain gets a better workout when you change your routine, say scientists at the California Institute of Technology who have pinpointed one particular circuit that activates your ability to execute a decision. This finding may help drive research in neural prosthetics and in how unhealthy decisions are made.

"How you decide to do things is fascinating, and not well understood," says Richard Andersen, Caltech's Boswell Professor of Neuroscience and senior researcher in the study. "We're looking at how different areas interact during the process--how you make a decision to plan a movement."

Andersen and his two collaborators focused on the cortex, the part of the brain where language, memories, and awareness of the outside world develop. They found that when choices are open, the brain's frontal and parietal cortices relay clear signals back and forth. In contrast, when a decision and the path to execute it are dictated, the correlation between these regions is significantly weaker.

"These findings show that different parts of the brain are working together. The premotor region--in the frontal cortex--first forms the plan; then once the signal travels to the parietal cortex, this second region sends back a 'handshake' as if to say, 'okay, I got it,'" explains Andersen.

To examine the circuit involved in decision making, two adult male monkeys were first dictated a specific sequence in which to touch three different shapes on a touch-sensitive screen in order to win a sip of liquid. After that, they were presented with a screen showing all circles, and only a randomly picked circle yielded the reward. Each monkey touched the circles in varying orders from trial to trial, suggesting he was making his own decisions. "When only circles are displayed, he knows the choices are free and that he'll get rewarded eventually," Andersen notes.

During these trials, tiny wires were planted close to neurons in both cortical areas. There are no pain endings in the brain, so the monkeys did not feel any discomfort, but the wires allowed the neural signals, the pulse-like waves of voltage called action potentials, to be recorded. A frequency band of the action potentials from a cell in one cortical area often matched a frequency band of the local field--a local voltage oscillation related to the synaptic potentials--in the other area. When the monkey was making his own choices, this correlation, or coherence, was significantly stronger than when he was following instructions.

"It may be more difficult to make your own choices, and this may be related to the increased coherence," Andersen remarks. "The cells that show coherence were also the first to show the direction the monkey chose to go," he adds, noting also that the short duration of coherence likely reflects that the decision is made very early on.

While the scenario examined here focused on situations that are immediately rewarded, Andersen says, "Even the long-range decisions that are made in other areas require this circuit to put them into play."

The implications for this research are manifold. "How does someone form preferences and plan movements to control a prosthetic arm, for example?" Andersen remarks. He also notes that mental illness, aging, or even fatigue, not to mention the extreme case of addiction, can drive unhealthy choices. Once the regions of the brain responsible for free choice are deciphered, poor decision making may also be better understood.

Other authors on the study, appearing April 16 in the early online edition of the journal Nature, are Bijan Pesaran, a former Caltech postdoc with Andersen and now an assistant professor at New York University, and Matthew Nelson, a Caltech graduate student in computation and neural systems. 

 

 

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Sixth Annual Caltech Science Writing Symposium

PASADENA, Calif.-California Institute of Technology President Jean-Lou Chameau and Pulitzer Prize-winning journalist Usha Lee McFarling will be the featured speakers at the sixth annual Caltech Science Writing Symposium. The topic of their conversation will be the importance and challenges of communicating science to the general public.

The symposium will take place on Friday, February 29, at 4 p.m., at Beckman Institute Auditorium on the Caltech campus. The event is free and open to the public.

As a civil and environmental engineer and president of one of the world's leading academic institutions, Chameau addresses diverse groups and often must communicate complex issues to audiences with varying ranges of scientific knowledge.

And as a former science journalist for the Los Angeles Times, McFarling, on a daily basis, had to clearly communicate technical concepts to the general public. Her recent series of articles, "Altered Oceans," which examines how ocean pollution threatens sea life and human health globally, won not only the Pulitzer Prize, but also awards from the American Association for the Advancement of Science, the American Geophysical Union, and the National Association of Science Writers. McFarling also wrote for the Knight Ridder Washington bureau and the Boston Globe.

Together, Chameau and McFarling will discuss the difficulties of conveying scientific information to nonspecialists and will share their insights and tips for communicating effectively.

The symposium is presented by the Words Matter program and Caltech's Division of Humanities and Social Sciences.

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Wine Study Shows Price Influences Perception

PASADENA, Calif.-- A rose by any other name might smell as sweet, but slap on a hefty price tag, and our opinion of it might go through the roof. At least that's the case with the taste of wine, say scientists from the California Institute of Technology and Stanford University.

Antonio Rangel, an associate professor of economics at Caltech, and his colleagues found that changes in the stated price of a sampled wine influenced not only how good volunteers thought it tasted, but the activity of a brain region that is involved in our experience of pleasure. In other words, "prices, by themselves, affect activity in an area of the brain that is thought to encode the experienced pleasantness of an experience," Rangel says.

Rangel and his colleagues had 20 volunteers taste five wine samples which, they were told, were identified by their different retail prices: $5, $10, $35, $45, and $90 per bottle. While the subjects tasted and evaluated the wines, their brains were scanned using functional magnetic resonance imaging, or fMRI.

The subjects consistently reported that they liked the taste of the $90 bottle better than the $5 one, and the $45 bottle better than the $35 one. Scans of their brains supported their subjective reports; a region of the brain called the medial orbitofrontal cortex, or mOFC, showed higher activity when the subjects drank the wines they said were more pleasurable.

There was a catch to the experiment, however. Although the subjects had been told that they would taste five different, variously priced wines, they actually had sampled only three. Wines 1 and 2 were used twice, but labeled with two different prices. For example, wine 2 was presented as the $90 wine (its actual retail price) and also as the $10 wine. When the subjects were told the wine cost $90 a bottle, they loved it; at $10 a bottle, not so much. In a follow-up experiment, the subjects again tasted all five wine samples, but without any price information; this time, they rated the cheapest wine as their most preferred.

Previous marketing studies have shown that it is possible to change people's reports of how good an experience is by changing their beliefs about the experience. For example, says Rangel, moviegoers will report liking a movie more when they hear beforehand how good it is. "Our study goes beyond that to show that the neural encoding of the quality of an experience is actually modulated by a variable such as price, which most people believe is correlated with experienced pleasantness," he says.

The experiment doesn't reveal whether the subjects truly experienced more pleasure from the wines that they thought were more expensive. "The area of their brain that is thought to encode for the pleasantness of the experience was more active when they drank wine they believed had higher prices. Strictly speaking, that is the only hard finding of the paper," he says. However, he adds, "it is hard to believe that this is not affecting their actual experience somehow, but we don't have hard evidence for that."

The results, while puzzling, actually make intuitive sense, Rangel says: "The brain encodes pleasure because it is useful for learning which activities to repeat and which ones to avoid, and good decision making requires good measures of the quality of an experience." But the brain is also a noisy environment, and "thus, as a way of improving its measurements, it makes sense to add up other sources of information about the experience. In particular, if you are very sure cognitively that an experience is good (perhaps because of previous experiences), it makes sense to incorporate that into your current measurements of pleasure." Most people believe, quite correctly, that price and the quality of a wine are correlated, so it is therefore natural for the brain to factor price into an evaluation of a wine's taste.

Could the findings be used by marketers to mess even more with consumers' heads? "Not directly," Rangel says. "But it certainly points out a channel through which prices affect the consumer experience and thus sales."

The paper, "Marketing actions can modulate neural representations of experienced pleasantness," was published January 14 in the early online edition of the Proceedings of the National Academy of Sciences.

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Kathy Svitil
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Attractiveness Is Its Own Reward

PASADENA, Calif. --Studies of the snap judgments we often make about people are shedding new light not only on social behavior, but also on drug abuse, gambling addiction, and other disorders in which our ability to make decisions is impaired, say scientists at the California Institute of Technology.

An emotional decision, such as forming an immediate like or dislike upon a first encounter with a new person, often occurs abruptly and automatically-and that impression can be difficult to change. To decipher the neurological underpinnings of those decisions, which will help explain the unique neurological characteristics of emotion, Hackjin Kim, a former postdoctoral scholar at Caltech who is now an assistant professor at Korea University--along with Ralph Adolphs, a professor of psychology and neuroscience, John O'Doherty, an associate professor of psychology, and Shinsuke Shimojo, a professor of biology--used a novel technique to monitor the activation of two brain regions during decision-making tasks.

In the first experiment, volunteers were briefly shown alternating pictures of two similar faces and asked which of the two they preferred. In the second experiment, the subjects were asked to decide which of two alternating faces looked more round. In both trials, the two faces were flashed back and forth, which extended the length of time the subjects needed to come to a conclusion and allowed the experimenters to see brain activation as the subjects formed a preference for one face over the other. The subjects' brains were scanned continuously using functional magnetic resonance imaging as they initially viewed the faces, made their decisions, and pressed buttons to enter their selections.

The brain scans showed that when the subjects were presented with the two faces for the first time, the nucleus accumbens (NAC), a collection of neurons located deep within the forebrain, was activated; activity in the NAC did not increase, however, when the subjects were presented with the faces a second time, during either experiment. This suggests that the NAC might be integral to the first impression we have when we see a new face or any novel item.

A second brain structure, the orbitofrontal cortex (OFC), which is located in the forebrain just above the orbits of the eyes, became more activated as the subjects actually selected which of the two faces they preferred, and also when they made their choices during the roundness experiment. This implies, the researchers say, that the OFC uses the initial preferences generated by the NAC to guide it in making more complex decisions.

Previous studies have shown that the NAC is the key structure in the brain responsible for reward, motivation, and addiction; the OFC is crucial for higher cognitive functions such as decision making.

The finding that neural structures implicated in reward should also be involved in these types of preferences makes sense, Adolphs says: "The idea is that when we choose which of two people we prefer, we find the one that we choose more rewarding. The same brain regions that are known to be involved in reward for many other kinds of things in the world are also engaged when we decide among people's faces. Evidently, looking at an attractive face is a reward. That is why we look there."

Deciphering how the NAC and OFC tick, the researchers say, could help us better understand decision making in general, which could eventually lead to new ways to treat disorders that affect this ability.

"There are many extremely important disorders of decision making and reward processing," such as drug and gambling addiction, Adolphs says. "People who are addicted to a drug make poor decisions that contribute to their difficulty in abstaining from it, and people who gamble often also make poor decisions, and continue to gamble despite the fact that they see they are losing money."

Even normal aging can compromise the function of the OFC and similar brain regions, with the result that "some elderly people make bad decisions," Adolphs says.

In all of these cases, he says, "Understanding at what point in the decision-making process an impairment arises will contribute substantially to clinical intervention." Thus, the paper is important not only to understanding social preferences, but also to a variety of issues in reward and addiction research.

The paper, "Temporal isolation of neural processes underlying face preference decisions," was recently published in the early online edition of the Proceedings of the National Academy of Sciences.

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Certain Types of Brain Damage Can Improve Utilitarian Moral Judgments, Research Shows

PASADENA, Calif.—Quick response! What's the best thing to do on a lifeboat with one too many people on board? Should one throw a mortally injured person overboard to ensure definite survival for everyone else, or refuse to act and ensure certain death for all individuals in the boat?

For most of us, the biggest stumbling block is the word "quick." Many of us will eventually concede that the greatest good for the greatest number of people is the only reasonable alternative, and that the injured person will have to be thrown overboard. However, we typically blanch at grim decisions involving actions that in other contexts would clearly be deemed immoral. Some people, in fact, never reach the utilitarian conclusion, saying that they would not be able to throw the injured person overboard, regardless of the final outcome.

But new research reveals that there is one type of person who can quickly reach the decision to act in the greater interest of the majority—the person who has suffered damage to an area of the brain known as the prefrontal cortex. In the current issue of the journal Nature, researchers from the California Institute of Technology, Harvard University, the University of Iowa, and the University of Southern California report that experimental tests on patients with prefrontal cortex damage reveal for the first time that emotions play an important role in feelings about what is right and wrong.

According to Ralph Adolphs, who holds joint appointments at Caltech and the University of Iowa Department of Neurology where the patients were tested, the results are important because they transfer the study of moral judgments from the realm of philosophical speculation to the realm of the experimental laboratory.

"The idea that emotions play a part in moral judgments is not new, but our study gives a stronger conclusion because it involves data from lesion subjects," says Adolphs.

The experiment was performed on six patients who have had tumors removed from the prefrontal cortex, 12 patients with other types of brain damage, and 12 healthy subjects. Each of the 30 test subjects was asked 50 questions involving moral dilemmas. Each question required a "yes" or "no" response, and the questions varied from easy nonmoral to very agonizing moral dilemmas (like throwing the person out of the lifeboat).

By significant margins, the six test subjects with prefrontal cortex damage were able to quickly arrive at the utilitarian response that saved the greater number of people. All the others had difficulty making those choices, and occasionally were unable to provide a "yes" answer even when the "no" scenario for action led to a greater number of people being injured or killed.

"These patients' judgments are different from the comparison subjects' judgments specifically for these high-conflict personal moral dilemmas," Adolphs explains. "Because of their brain damage, they have abnormal social emotions in real life, and lack a normal concern for the well-being of others. In other words, they lack empathy and compassion.

"So patients with prefrontal damage usually say it's preferable to throw the injured person overboard, and they don't have the conflict between emotion and reason that other people have."

The conclusion is that emotions indeed play a role in moral decisions, especially those involving questions of whether the end justifies the means. In short, the people with the brain damage are quickly able to "do the arithmetic" that determines who lives and who dies.

Adolphs is the Bren Professor of Psychology and Neuroscience and professor of biology. The lead authors of the study are Michael Koenigs and Liane Young, at the National Institute of Health and Harvard University, respectively. The other authors are Daniel Tranel of the University of Iowa, Fiery Cushman and Marc Hauser, both of Harvard, and Antonio Damasio, formerly of the University of Iowa and now at the University of Southern California.

The title of the paper is "Damage to the Prefrontal Cortex Increases Utilitarian Moral Judgments."

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Robert Tindol
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Watson Lecture: European Conquest

PASADENA, Calif.--How did the West conquer the world? The secret, says California Institute of Technology economic historian Philip T. Hoffman: technological innovation.

Between 1500 and 1914, European states conquered 84 percent of the globe, although the weapons they employed--gunpowder and firearms--were invented in China and were long used in other parts of Eurasia. Why didn't the Chinese, the Japanese, or the Ottomans perfect this technology?

Using economic calculations, Hoffman measured the European advantage and concluded that European political institutions drove military innovation with incentives much like those at work today in Silicon Valley. "The rates of technological innovation were far higher than you'd expect before the industrial revolution, and similar to what you see today in the computer industry," he says. Military adventures had potentially great rewards for decision makers, with very little penalty for failure. As a result, "you had excessive investment in this sector of the economy."

On Wednesday, December 6, Hoffman, the Richard and Barbara Rosenberg Professor of History and Social Science at Caltech, will discuss his findings in "Why Did Europe Conquer the World?" The lecture will be presented at 8 p.m. in Beckman Auditorium, 332 South Michigan Avenue, south of Del Mar Boulevard, on the Caltech campus in Pasadena. It is the third program of the fall/winter 2006-07 Earnest C. Watson Lecture Series. Seating is available on a free, no-ticket-required, first-come, first-served basis.

Caltech has offered the Watson Lecture Series since 1922, when it was conceived by the late Caltech physicist Earnest Watson as a way to explain science to the local community.

For more information, call (626) 395-4652. Outside the greater Pasadena area, call toll-free, 1(888) 2CALTECH (1-888-222-5832).

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Contact: Kathy Svitil (626) 395-8022 ksvitil@caltech.edu

Visit the Caltech Media Relations website at: http://pr.caltech.edu/media.

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Caltech and Princeton University Press Release Tenth Volume of the Einstein Papers

PASADENA, Calif.-In the latter half of 1920, Albert Einstein faced a series of increasingly acrimonious public attacks against his recently confirmed theory of general relativity. He considered leaving Berlin, which would have deprived Germany of its most famous scientist. Colleagues, friends, and unknown admirers offered support, while Einstein worried about the care of his two sons and ex-wife in Switzerland, and his new family in Berlin.

This is the historic context of the tenth volume of The Collected Papers of Albert Einstein, which is being released this week by Princeton University Press under the editorship of the Einstein Papers Project at the California Institute of Technology.

Volume 10 contains Einstein's correspondence from May to December 1920, as well as a substantial number of previously unavailable letters from 1909 to 1920, most of them written by Einstein. These originate from the bequest of family correspondence deposited at the Albert Einstein Archives at the Hebrew University in Jerusalem by his stepdaughter Margot Einstein, who stipulated that they remain closed for twenty years after her death.

The volume presents letters written by Einstein's young sons Hans Albert and Eduard Einstein in which they report on their hobbies and reading and express their longing for the absent father. It also includes for the first time since Volume 1 a number of letters written by his wife, Mileva Einstein-Maric. The largest group of supplementary letters, written by Einstein between April 1916 and October 1919, mainly in the form of postcards and resembling a travel diary, is addressed to Elsa Einstein, his cousin and future second wife.

It also contains new information on Einstein's personal life during the last eight months of 1920, such as his first vacation with his sons in Southern Germany and his renewed attempts to move his Zurich family there. We also gain a glimpse into the unique perspective of Elsa Einstein, in the few extant letters, of her relationship to Einstein.

In addition, in letters newly available at the Central Library in Zurich addressed to his friend Heinrich Zangger, Einstein confides on personal matters, worries, and family crises, his negotiations with Mileva Einstein-Maric, his feelings about his sons, the separation, divorce, and contemplated second marriage. The war, his opposition to it, and his sense of alienation from some of his academic colleagues in Berlin come to the fore, as do the difficulties of crossing international borders, the widespread hunger, and economic hardships.

The second half of Volume 10 finds Einstein full of optimism about Germany's new democracy. He vigorously promotes general relativity and the endeavors of other scientists toward its further confirmation. We see Einstein firmly positioned as a central figure in the lively cultural atmosphere of the young Weimar Republic, as witnessed by correspondence with renowned German philosophers of the time, such as Ernst Cassirer, Hans Reichenbach, and Max Wertheimer.

Scientific issues are discussed in the correspondence as well, shedding light on his associations with fellow physicists in Europe and the United States, and his lectures on the special and general theories of relativity within Germany and during his trips to Holland, Denmark, and Norway. The documents present the challenges Einstein faced as a result of his recently acquired celebrity status, his subsequent entrance into the public arena, and the contentious public attacks against relativity.

The intensity of this period, during which anti-Semitism and nationalistic sentiment seeped into scientific debate, is reflected in numerous letters. The successful completion of the intricate process of Einstein's appointment as Special Professor at the University of Leyden leads to his well-known inaugural lecture on "Ether and Relativity" in October 1920. The letters document in detail his sojourns in the Netherlands, the hospitality of many Dutch colleagues, his involvement with issues at the forefront of physics, and especially his significant intellectual and personal bonds with Paul Ehrenfest. He visits Oslo and Copenhagen, where he meets with Niels Bohr, and receives invitations to America.

The Collected Papers of Albert Einstein, a collaborative project with participants from several countries, are edited by Diana Kormos-Buchwald, a professor of history at Caltech; Tilman Sauer, a senior research associate in history; Ze'ev Rosenkranz, Jozsef Illy, and Virginia Iris Holmes, members of the research staff in the Einstein Papers Project; and by associate editors Jeroen van Dongen, Daniel Kennefick, and A.J. Kox.

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