PROFILE

Profile of Philip N. Johnson-Laird

ur greatest technological doctorate on psycholinguistics and dem- accomplishments, from space onstrated the importance of pragmatic, or Otravel to nuclear power and the contextual, factors in language. The re- creation of the Internet, stand as sults acted as a counterbalance to the testaments to the scientific process and prevailing notion of so-called “trans- mankind’s ability to . These ad- formational” grammar, which relates in- vances, however, have been matched with tended meanings with actual spoken equally spectacular technological cata- words. This theory, developed by pre- strophes. “Scientists and technologists are eminent cognitive scientist Noam Chom- rational in principle,” explains Philip sky, had gained much prominence in the Johnson-Laird, a professor of early 1960s. at Princeton University and recently “Transformational grammarians ar- elected member of the National Academy gued that active and passive sentences of Sciences. “But the more information had the same underlying, or ‘deep,’ syn- they have to take into account, the more tax. My work showed that factors such as working memory they need and the the use of active or passive voice affected longer time it takes them to make an in- people’s understanding of a sentence. ference.” When complex technology starts Deep syntax was not the only thing that spiraling out of hand, this abundance mattered” (1). “In truth, I don’t think of information hinders our ability to Chomsky ever that deep struc- make reliable decisions. “Eventually,” ture was the only thing that mattered in Johnson-Laird says, “the computational interpretation, but maybe some linguists demands overwhelm them, and this often influenced by him did.” Johnson-Laird culminates in catastrophes.” completed his doctorate in only 2 years, Johnson-Laird has been studying the Philip N. Johnson-Laird. and stayed on as a lecturer at Uni- human ability to reason for nearly a half versity College. a century. His theory of mental models, Further research by Johnson-Laird and which outlines how real or imaginary “I knew by then that I wanted an ‘in- Wason similarly undermined long-held situations are represented in the brain, teresting job,’ something in the sciences,” views about how we reason. Together, the has challenged long-held assumptions he recalls. However, because he had duo explicitly challenged theories set about how humans think. “ dropped out of school before receiving forth by another influential psychologist, theory implies that we are rational because his diploma, he knew it would be . “Beginning with Piaget, who we grasp that an inference is no good difficult to learn the material necessary to is considered the godfather of studies of if we can think of a counterexample to it,” pass the prerequisite examinations in children’s intellectual development, some he says. “In practice, however, we often science on his own. He therefore opted scientists believe that humans construct err, failing to find, search for, or heed for psychology, then classified both as a mental as a result of experience,” a counterexample.” science and art. He passed the British explains Johnson-Laird. “Of course, we’re A-levels and attended University College, not normally aware of logical rules when A Peripatetic Past London. The academic lifestyle suited we reason or grammatical rules as we Born in 1936 in a suburb of the northern Johnson-Laird well. “By the time I got speak, but Piaget’s work was taken up by English city of Leeds, Johnson-Laird to university I was 25,” he explains. “I was students of human reasoning.” left school at the age of 15. He took work older than anybody else in my class.” With Wason, Johnson-Laird undertook as a surveyor—a job he held for 5 years However, that didn’t matter, he tests of and de- despite “really hating it.” Toward the end says, because “psychology was much termined that the content of reasoning of this position, he became active in more interesting than anything I’d ever plays a major role in the accuracy of politics and joined the Campaign for done before.” conclusions (2). Given descriptions of Nuclear Disarmament. He met and mar- simple regulations about the postal ser- ried his wife of more than 50 years, Content, Not Form vice, for example, individuals produced Maureen Sullivan, during this tumultuous Although he had not planned to remain at more accurate conclusions than when time. They took part in demonstra- University College after receiving his given similar rules about abstract rela- tions and civil disobedience with the undergraduate degree, a casual remark tions between objects with which they Committee of 100, the group founded from the chair of his department sealed his were familiar, such as numbers and let- in 1960 by the philosopher Bertrand future. “George Drew, who was tran- ters. “According to followers of Piaget, Russell to protest Britain’s possession of sitioning the department into the bi- mental logic should not be affected by nuclear weapons. ological sciences, said to me something content,” says Johnson-Laird. “Our re- After refusing Britain’s then-mandatory along these lines: ‘Of course you’ll be sults were not, I think, something that national military service, Johnson-Laird staying on to do a PhD.’ That took me people immediately appreciated. But they took a series of jobs as a hospital porter, aback, but I went with it.” did imply that the mind does not contain a librarian, and a baker. Musically in- The question, then, was what to study? a logic made up of formal or explicit rules clined, he moonlighted for a time as Johnson-Laird began working under the of inference.” a modern jazz pianist and gave talks direction of cognitive psychologist Peter about music on BBC radio. His family Wason, who had just returned from a stint “ ” ’ fl had no real academic tradition at all at Harvard University sin uential Center fi ’ This is a Pro le of a recently elected member of the Na- but as he neared his midtwenties, John- for Cognitive Studies. Under Wason s tional Academy of Sciences to accompany the member’s son-Laird decided to attend university. guidance, Johnson-Laird pursued his Inaugural Article on page 18243 in issue 43 of volume 107.

www.pnas.org/cgi/doi/10.1073/pnas.1117174108 PNAS Early Edition | 1of3 Downloaded by guest on September 28, 2021 Process, Not Product Laird went on to discover that the greater dent, Sangeet Khemlani, he hopes to Johnson-Laird spent the early 1970s at the number of models humans have to con- combine previously separate programs for Institute for Advanced Studies in Prince- struct, the greater the likelihood that we reasoning into one unified algorithm for ton, where he began a 5-year collaboration will draw an incorrect conclusion, as in . the case of some technological cata- with George A. Miller, who had moved Beyond Reason there from Harvard. In 1976, he and strophes. In 1983, he published a book on fl Miller published Language and Percep- the subject, Mental Models, which in- His expansive curiosity, re ected from an tion, a book that detailed how humans tegrates the psychology of reasoning and early age in his evolving interests, have understand language. In it, Johnson-Laird the psychology of meaning (6). It has pushed Johnson-Laird toward research in fi and Miller argued that humans create since been a cornerstone in the eld. areas related to but not explicitly about mental representations of what they hear By then, Johnson-Laird had joined reason. , for example, are often or read—an idea that presaged mental a research unit in Cambridge, England, thought of as directly opposed to reason. model theory (3). Johnson-Laird explains, directed under the auspices of the British However, Johnson-Laird has demon- “As people understand a sentence, it’sas Medical Research Council. He and Ruth strated that emotions can improve our though they are setting up a computer Byrne, now a professor at Trinity College, logical conclusions. Together with psy- program. When that program runs, it Dublin, extended the theory of mental chologist Keith Oatley, now a professor yields a representation of the meaning of models to address reasoning about spatial emeritus at the University of Toronto, that sentence—almost like a bit of men- relations, conditional assertions, and dis- he embarked on an investigation of ” junctions—covering, in principle, the emotions (9). tal theater. “ Based on this idea, Johnson-Laird and same ground as formal logic (7). Evolutionarily, emotions are very old. his colleague Mark Steedman, a cognitive They predate human beings, so it stands Illusory Inferences to reason that they might affect our linguist now at the University of Edin- Aided by his former collaborator George thought processes,” he says. After un- burgh, developed computer programs that Miller, the department of psychology at dertaking an initial study, Johnson-Laird modeled aspects of human comprehen- Princeton University recruited Johnson- and Oatley proposed that individuals sion (4). Since then, Johnson-Laird has Laird in 1989, where he became the Stuart could experience only one basic enjoyed relying on computer models to Professor of Psychology in 1994. Further at a time; for example, they could feel implement his ideas about language and research on human participants as well sad, and then angry, but not both simul- reasoning. “If you’re lucky, two things as in silico experiments uncovered one taneously. “Based on Oatley’s and happen,” he says. “First, the computer of the “predictable illusions” that bedevil others’ empirical research, we discovered model may suggest a neat experiment to humans when we reason. To save that this claim was false,” Johnson-Laird test your theory. Second, the model may brainpower and avoid overloading our says. “But it helped us to improve make a prediction that had never oc- memory, we construct only mental mod- the theory.” curred to you—that might even strike ” els of the truths in a possible scenario, This work also helped Johnson-Laird you, initially, as crazy. rather than what is false. This shortcut conceive the hyper emotion theory of Mental Model Manifesto leads to so-called “illusory inferences”— psychological illnesses. He developed the misconceptions capable of crippling both theory with Italian psychiatrist Francesco After his visit to Princeton, Johnson-Laird high-tech and commonplace endeavors. Mancini of the Association of Cognitive accepted a position in experimental psy- “These results damage the case for Psychology in Rome and clinical psy- chology at the University of Sussex, where explicit rules of logic,” Johnson-Laird chologist Amelia Gangemi of the Uni- he remained until 1982. There, as he concludes. “In very broad terms, we’re versity of Messina in Sicily. The group continued to examine how humans reason, not as imbued with a formal logic as some showed that individuals who suffer from he took ideas from his earlier studies of philosophers, logicians, and psychologists depression, obsessive-compulsive disor- language comprehension and began to think we are. Logic, I believe, is rather der, or agoraphobia actually reason better think about their implications for rea- a cultural invention. But everybody has than healthy individuals—although only soning. An essential question remained the ability to imagine possibilities, and to about topics related to their illnesses (10). “ unanswered: What constitutes the realize that an inference is not valid if “If you look at these disorders, there’s ” mental representation of discourse? there’s a possibility in which the premises always a basic emotion at stake,” John- At a seminal lecture delivered in San hold, but the conclusion does not.” son-Laird says. “A stimulus provokes this Diego in 1980 at the first meeting of the In his Inaugural Article, Johnson-Laird emotion, which helps patients reason Cognitive Science Society, Johnson-Laird summarizes decades of research, lead- well. The intensity of the emotion, how- both answered this question and de- ing readers through the frailties and ever, is ultimately the root of the illness.” fended an integrated discipline of cogni- strengths of human reasoning. He offers a In addition to studying the effects of tive science, which then existed as a definitive statement on this paramount emotions on the human ability to reason, hodgepodge of fields including psychol- human ability: “Our ability to reason is Johnson-Laird has continued to make ogy, , anthropology, neurosci- not simple, neat, and impeccable—it is music—currently, a set of symphonic ence, and (5). not akin to a proof in logic. Instead, it variations inspired by the English mod- “At the meeting, I put forward the draws no clear distinction between de- ernist composer Alan Rawsthorne—and theory that we reason by imagining a sit- duction, induction, and abduction, because to study its cognitive roots, such as the uation in which the premises are true— it tends to exploit what we know” (8). causes of musical dissonance. Johnson- that is, we construct a mental model of Johnson-Laird is currently developing Laird is also constructing algorithms that them. In the case of some premises, we an integrated computer implementation generate novel chord sequences and may have to construct multiple models to of the mental model theory—one that melodies (11). As he plans his transition capture multiple possibilities. A conclu- evaluates arguments stated informally, as from teaching psychology courses in the sion is necessary if it holds in all the we normally speak, and one that predicts summer of 2012, he hopes to focus his models of the premises; it is probable if it our likely responses to these arguments. attention on musical improvisation as well holds in most of them; and it is possible if Working with several longtime collabo- as continue writing programs to simulate it holds in at least one of them.” Johnson- rators, including his former doctoral stu- mental processes.

2of3 | www.pnas.org/cgi/doi/10.1073/pnas.1117174108 Ahmed Downloaded by guest on September 28, 2021 An understanding of reasoning, John- pher [Gottfried] Leibniz said that the “I’ll settle for a mechanical way to test the son-Laird notes, has perhaps been as great goal for students of human reason- validity of inferences in daily life.” paramount a human activity as the ability ing was to develop a mechanical way to to reason itself. “The German philoso- resolve arguments,” says Johnson-Laird. Farooq Ahmed, Freelance Science Writer

1. Johnson-Laird PN (1968) The interpretation of the 5. Johnson-Laird PN (1980) Mental models in cognitive 9. Johnson-Laird PN, Oatley K (2000) Cognitive and so- passive voice. Q J Exp Psychol 20:69–73. science. Cogn Sci 4:71–115. cial construction in emotions. Handbook of Emotions, 2. Johnson-Laird PN, Wason PC (1970) A theoretical 6. Johnson-Laird P (1983) Mental Models: Towards eds Lewis M, Haviland-Jones JM (Guilford, New York), analysis of insight into a reasoning task. Cognit Psychol a Cognitive Science of Language, Inference, and Con- 2nd Ed, pp 458–475. 1:134–148. sciousness (Harvard Univ Press, Cambridge, MA). 10. Johnson-Laird PN, Mancini F, Gangemi A (2006) A hy- 3. Miller GA, Johnson-Laird PN (1976) Language and 7. Johnson-Laird PN, Byrne RMJ (1991) Deduction (Erl- per-emotion theory of psychological illnesses. Psychol Perception (Harvard Univ Press, Cambridge, MA). baum, Hillsdale, NJ). Rev 113:822–841. 4. Johnson-Laird PN, Steedman MJ (1978) The psychology 8. Johnson-Laird PN (2010) Mental models and human 11. Johnson-Laird PN (2002) How jazz musicians impro- of syllogisms. Cognit Psychol 10:64–99. reasoning. Proc Natl Acad Sci USA 107:18243–18250. vise. Music Percept 19:415–442.

Ahmed PNAS Early Edition | 3of3 Downloaded by guest on September 28, 2021