Farooq Ahmed

Profile of Philip N. Johnson-Laird

Our greatest technological accomplishments, from space travel to nuclear power and the creation of the Internet, stand as testaments to the scientific process and mankinds ability to reason. These advances, however, have been matched with equally spectacular technological catastrophes. “Scientists and technologists are rational in principle,” explains Philip Johnson-Laird, a professor of psychology at Princeton University and recently elected member of the National Academy of Sciences. “But the more information they have to take into account, the more working memory they need and the longer time it takes them to make an inference.” When complex technology starts spiraling out of hand, this abundance of information hinders our ability to make reliable decisions. “Eventually,” Johnson-Laird says, “the computational demands overwhelm them, and this often culminates in catastrophes.” Philip N. Johnson-Laird. Johnson-Laird has been studying the human ability to reason for nearly a half a century. His theory of mental models, which outlines how real or imaginary situations are represented in the brain, has challenged long-held assumptions about how humans think. “Mental model theory implies that we are rational because we grasp that an inference is no good if we can think of a counterexample to it,” he says. “In practice, however, we often err, failing to find, search for, or heed a counterexample.” Born in 1936 in a suburb of the northern English city of Leeds, Johnson-Laird left school at the age of 15. He took work as a surveyor—a job he held for 5 years despite “really hating it.” Toward the end of this position, he became active in politics and joined the Campaign for Nuclear Disarmament. He met and married his wife of more than 50 years, Maureen Sullivan, during this tumultuous time. They took part in demonstrations and civil disobedience with the Committee of 100, the group founded …

Profile of Peter R. Grant

In 1940, as the Second World War escalated, 4-year-old Peter Grant was evacuated from London to a school in the English countryside on the Surrey–Hampshire border. Far from being traumatized by his sudden relocation, Grant, already a budding naturalist, remembers those years fondly. Peter Grant. “Our school was in the middle of fields with access to a little bit of forest,” he recalls. “I was just fascinated by the great big diversity of organisms that live in the outside world.” Safe from the destruction in London, Grant collected butterflies, watched birds, and identified flowers. This early experience helped shape his career in ecology and evolutionary biology, which has resulted in some remarkable accomplishments. Grant is now an emeritus professor and Class of 1877 Professor of Zoology at Princeton University (Princeton, NJ). He was elected to the National Academy of Sciences in 2007. Grant and his wife Rosemary, who was elected to the Academy in 2008, received the Kyoto Prize in Japan in December 2009. No strangers to international acclaim, the Grants are also members of the Royal Society of London, the Royal Society of Canada, and have won the Royal Society Darwin Medal, the Darwin-Wallace Medal of the Linnean Society, and the Balzan Foundation Prize. Grant’s Inaugural Article in the November 16, 2009 issue of PNAS details both the random and deterministic processes that can influence the development of a species (1). Grant and his wife observed the immigration in 1981 of a medium ground finch ( Geospiza fortis ) to Daphne Major, the small volcanic island in the Galapagos chain that has played host to much of the couple’s research. The lone bird was unusual in many respects; it sang an atypical song, was larger than similar birds, had a pointed, oversized beak, and contained alleles that marked it as a …

QnAs with Donald Geman

With the proliferation of “omics” technologies, personalized medicine—which tailors treatment to an individual’s genomic profile—promised a revolution in care. That revolution, says applied mathematician Donald Geman, has been slow to arrive. Geman has spent nearly four decades devising statistical methods for a variety of applications. He recently teamed up with an interdisciplinary group of scientists at The Johns Hopkins University, where he is a professor of applied mathematics and holds appointments at the university’s Institute for Computational Medicine and Center for Imaging Science. Geman helped engineer an algorithm that reduces data complexity and may assist in differentiating between certain forms of cancer. This work builds on his earlier research in computer vision, leveraging his experience with pattern-recognition problems. PNAS recently spoke to Geman, who was elected to the National Academy of Sciences in 2015, about his current research. Donald Geman. Image courtesy of Donald Geman. > PNAS:We have been hearing about personalized medicine for at least a decade. What are some of the challenges researchers face? > Geman:Personalized medicine hasn’t yet reached a point where it is deployable on a mass scale, and there are many reasons for this. Genomic data are incredibly complex due to the interactions among gene products, as well as heterogeneity both within and between patients. All of it …

QnAs with Shaul Mukamel

Since the invention of the laser in the 1960s, researchers have recognized that the device could be used to investigate atomic structure and nuclear motions. Over the course of his career, Shaul Mukamel, a professor of chemistry, physics, and astronomy at the University of California, Irvine, has advanced theories underlying nonlinear laser spectroscopy and imaging. Mukamel has shed light on the many uses of short laser pulses in medicine, in studies of electron and energy transfer, and in solar energy harvesting. Generations of scientists and engineers consider his 1995 book, Principles of Nonlinear Optical Spectroscopy (1), essential reading. Mukamel’s research focuses on the design of experiments that leverage light sources, such as X-ray free-electron lasers, that operate at femtosecond timescales. His Inaugural Article (2) demonstrates how short X-ray pulses can probe conical intersections, which are molecular geometries where electronic-state energies and vibrational energies become comparable. Based on the principle of quantum superposition, molecules exist simultaneously in both the ground and the excited state, an effect also known as the Schrodinger’s cat paradox. PNAS recently spoke to Mukamel, who was elected to the National Academy of Sciences in 2015. Shaul Mukamel. Image courtesy of Shaul Mukamel. > PNAS:In your Inaugural Article (2), you describe using a …

QnAs with Ewine F. van Dishoeck

In the last 15 years, two major international projects—the Herschel Space Observatory and the Atacama Large Millimeter Array (ALMA)—have transformed researchers’ ability to investigate interstellar space at the farthest reaches of the universe. The 2018 recipient of the James Craig Watson Medal of the National Academy of Sciences, Ewine F. van Dishoeck, has been involved in both projects from their inception. van Dishoeck’s research has revealed the chemistry of the cosmos on both macroscopic and microscopic levels, detailing the formation of stars and planets as well as the molecular composition of interstellar clouds, dust, and disks. Her work holds tantalizing clues about the development of water and organic matter—the building blocks of life as we know it—on Earth as well as on exoplanets. A professor of molecular astrophysics at Leiden University in The Netherlands, as well as the former director of Leiden’s Raymond and Beverly Sackler Laboratory for Astrophysics, van Dishoeck was elected as a foreign associate to the National Academy of Sciences in 2001. PNAS recently spoke to van Dishoeck about her research. Ewine F. van Dishoeck. Image courtesy of Elodie Burrillon (photographer). > PNAS:You started working on the European Space Agency’s …

QnAs with Helmut Schwarz.

In the early 1900s, German chemists Fritz Haber and Carl Bosch developed a way to synthesize ammonia from atmospheric nitrogen and methane-derived hydrogen. The method became a vital step in manufacturing not only fertilizers but also explosives. Haber likened the process to making “bread from air” (Haber and Bosch are both winners of Nobel Prizes in Chemistry). In his Inaugural Article (1), the chemist Helmut Schwarz has himself devised a method to “make bread from air,” synthesizing ammonia from nitrogen and hydrogen using the metal tantalum as a catalyst. A professor of chemistry at the Technische Universitat Berlin, Schwarz has uncovered the mechanisms of catalysis at an atomic level. He has identified so-called “aristocratic atoms,” which act as the workhorses of chemical reactions and has deepened our understanding of organometallic processes. Schwarz has also served as President of the Alexander von Humboldt Foundation, which supports international partnerships between scientists from Germany and around the world. PNAS recently spoke to Schwarz, who was elected as a Foreign Associate of the National Academy of Sciences in 2018, about his current research. Helmut Schwarz. Image courtesy of the Alexander von Humboldt Foundation/David Ausserhofer. > PNAS:In your Inaugural Article (1), you …

Q&As with Marsha I. Lester

Evidence of Earth’s changing environment is abundant, from diminished polar ice caps to increased frequency of catastrophic storms. However, the chemical reactions in our atmosphere that can contribute to a changing climate are less well known. A physical chemist at the University of Pennsylvania who studies the troposphere, Marsha I. Lester combines experiment, theory, and modeling to investigate the chemistry at the edge of our planet. Her group examines the oxidation of man-made and biogenic volatile organic compounds, such as alkenes. The reactions proceed through transitory species known as Criegee intermediates, which were first predicted in the 1950s but only recently observed. Lester’s group generated these intermediates, characterized them using spectroscopy, and measured the rates of their decay to hydroxyl radicals, which are key oxidants in the troposphere. The research has enriched our understanding of atmospheric chemistry and might reveal how the atmosphere can repair itself. PNAS recently spoke to Lester, who was elected to the National Academy of Sciences (NAS) in May 2016, about her current research. Marsha I. Lester. Image courtesy of Felice Macera (University of Pennsylvania, Philadelphia). > PNAS:Your work with Criegee intermediates reveals how oxidants in the troposphere can “cleanse” the atmosphere. How does this occur, and what …

QnAs with H. Vincent Poor

The proliferation of wireless devices in the last three decades has been heralded as a technological revolution. H. Vincent Poor, the Michael Henry Strater University Professor at Princeton University, has been studying these devices and the networks on which they run since their infancy, and has helped usher in the revolution. With a background in information theory, electrical engineering, and computer science, Poor has led formative research on signal processing, social networks, multiuser communications, and smart grids. PNAS recently spoke to Poor, who was elected to the National Academy of Sciences in 2011, about his current research. H. Vincent Poor. Image courtesy of David Kelly Crow (photographer). > PNAS:Your recent work examines security in the physical layer of wireless transmission. What is the physical layer, and why is security in this layer crucial? > Poor:Networks operate through multiple layers of infrastructure that encode, transmit, route, regulate, and decode information. Layering is a very important part of network design, and it is one of the reasons why networks are ubiquitous. The advantage of having layers is …

Profile of Helen M. Blau

The human ability to regenerate tissues is crucial to survival: wounds heal, broken bones knit, and livers regrow. However, the quality and length of life are constrained by limitations in this ability. Cardiac muscles do not regrow after infarction, and other damaged muscles rebuild with difficulty, especially with age. Helen M. Blau. Image courtesy of Amparo Garrido (photographer). Stanford University stem cell biologist Helen M. Blau has devoted her career to understanding how muscle cells regenerate. Her research has revealed insights into the genetic and cellular mechanisms underlying regeneration and related processes, such as differentiation, morphogenesis, and angiogenesis. Blau’s Inaugural Article demonstrates a method to treat damaged muscle by injecting the inflammatory mediator, prostaglandin E2, directly into the site of injury to spur muscle stem cell expansion and catalyze tissue repair (1). As the Donald E. and Delia B. Baxter Foundation professor, Blau directs the Baxter Laboratory for Stem Cell Biology at Stanford and was elected to the National Academy of Sciences in 2016. The daughter of a historian for the United States government and an instructor of comparative literature, Blau was born in England and experienced a culturally rich childhood. “My parents were Austrian and immigrated to the [United States] during World War II. We grew up listening to opera and living and travelling throughout Europe,” she recalls. She holds dual United States and British citizenship. Blau notes that in high school in Germany, she studied languages and literature. But as an undergraduate at the University of York in England, she chose to study biology and wrote a thesis on liver regeneration, foreshadowing her later interests. Her college advisor, biochemist J. Ramsey Bronk, the son of former National Academy of Sciences President Detlev Bronk, suggested she return to the United States to pursue graduate school, and in the …

Profile of Paul Slovic

On September 2, 2015, the image of three-year-old Syrian boy, Aylan Kurdi, lying face down on a Turkish beach sparked an international effort to aid refugees. Donations to charitable organizations surged, dwarfing the assistance to refugees since the violence in Syria began in 2011. Kurdi, however, was not the only person to drown that day in the Aegean Sea: Both his five-year-old brother and his mother died, as did several others. Paul Slovic. Image courtesy of Paul Slovic. According to research by psychologist Paul Slovic, the international response would have been less charitable had the public seen the other drowned refugees. “If we had seen just one more individual, our compassion toward them all might have faded,” he explains. “Several psychological phenomena, including psychic numbing, would have made us care less about their plight.” Slovic, who was elected to the National Academy of Sciences in 2016, studies human decision making and motivation. His Inaugural Article dissects the response to Kurdi’s death, enumerating the psychological obstacles to the human ability to care about mass atrocities. The article by Slovic et al. (1) also outlines techniques that can help face humanitarian crises without having to rely solely on compassion. A professor of psychology at the University of Oregon since 1986, Slovic also serves as the president of Decision Research, an institute that he helped found. Born in Chicago in 1938, Slovic had a peripatetic childhood. His family traveled across the Midwest (Illinois, Wisconsin, and Minnesota) with his salesman father. Slovic was drawn to basketball, and he received a scholarship to attend Chicago’s Depaul University. College basketball, however, proved challenging, and soon Slovic transferred to Stanford University. He credits psychologists Quinn McNemar and Lewis Goldberg with introducing him to psychological research methods and encouraging him to further his studies. Slovic received an undergraduate …