Psychological Science in the 21st Century

Psychology as a Hub Science

The first major change that has occurred over the past few decades concerns where psychology fits relative to other scientific disciplines. To determine how scientific disciplines are organized in the 21st century, Boyack, Klavans, and Börner (2005) quantified the patterns of scientific influence within and across the sciences based on citation data from more than 1 million journal articles appearing in 7,121 natural and social sciences journals published in 2000. They used these data to create a map of science. Specifically, they used eight different approaches to quantifying citation patterns to ensure structural accuracy (where accuracy means that journals within the same subdiscipline are grouped together and groups of journals that cite each other are close to each other). Boyack et al. also used new visualization techniques to generate a two-dimensional spatial map of the sciences based on each metric. They established the validity of these maps using two different accuracy measures. The resulting map of science, which is displayed in Figure 1, provided a visual depiction of where each scientific discipline lies, what disciplines surround it, how each discipline is related to neighboring disciplines, and how strongly each discipline impacts its neighbors.

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Figure 1.

Map of science generated using a similarity measure based on cocitations. Large font size labels identify major areas of science. Small labels denote the disciplinary topics of nearby clusters of journals. Adapted from Boyack, Klavans, and Börner (2005); From Cacioppo & Freberg, 2013.

Not surprisingly, given increases in scientific specialization over the past century, Boyack et al. found that scientific fields are organized around a small number of hub disciplines. From their data, Boyack and colleagues identified seven specific hub sciences: mathematics, physics, chemistry, earth sciences, medicine, psychology, and the social sciences. Yes, psychology emerged as a discipline whose research influences the work of scientists in many other fields. For instance, medicine draws upon psychology most heavily through neurology and psychiatry, whereas the social sciences draw directly from most of the specialties within psychology.

These findings have implications for how we teach our courses. For example, most students in our introductory psychology classes will major in other disciplines. We are largely ignoring these students to the extent that we teach introductory psychology as a prep course for subsequent psychology courses. This is because most of these students will never take an advanced psychology course. Should we be surprised, then, that these students, many of whom were ignored in our classes over the past few decades, now see little relevance of psychological science and are sitting on legislatures and school boards arguing to defund psychological science?

The results of Boyack et al.’ (2005) work also suggest that what our nonmajors learn in Introductory Psychology is likely to benefit them in whatever field they choose to major. As a consequence, we have the opportunity in our introductory psychology courses to teach our nonmajors what an exciting empirical science we represent. We also have the opportunity to show them that there are important differences between Dr. Phil and Dr. Laura—whose statements are often based solely on their particular beliefs—and psychological researchers—whose statements are based on scientific evidence. Thus, in addition to preparing our majors for advanced coursework in psychology, one of our goals in Introductory Psychology should be to teach our nonmajors the important impact that psychological science can have on their personal and professional lives.

More generally, Boyack et al.’s (2005) findings have implications for what happens at colleges and universities across the country. Most universities are organized along traditional disciplinary boundaries, and decisions about where to invest limited academic funds are often influenced by the return one can expect on those investments. Those who make decisions about faculties and facilities may, therefore, benefit by knowing something about the scientific disciplines that are especially central and influential. The results of Boyack et al.’s work suggest that investments in psychology will likely have benefits that extend well beyond the walls of psychology departments.

Psychology as an Interdisciplinary Science

A second key change in psychological science, and in science in general in the 21st century, is the rise in interdisciplinary, collaborative science. Traditionally, individuals have advanced scientific knowledge, and the reward structure in science reflects this tradition. Graduate students and junior faculty are admonished to establish their independence, which will allow them to show their genius while avoiding any attributional ambiguity that may result from collaborating with others. When a candidate for tenure fails to heed this advice and publishes as a member of a scientific team, external letter writers, faculty review committees, and university administrators are inclined to raise questions about the candidate’s contributions and scientific merit. The emphasis on the solitary production of knowledge does not stop with tenure either. Individual contributions are often paramount in the determination of raises and in the selection of recipients for scientific awards ranging from early-career awards to the Nobel Prize.

But evidence suggests that science is becoming more collaborative. Among the evidence is an article in Science by Wuchty, Jones, and Uzzi (2007), who examined all U.S. patents registered since 1975 and all research articles in the Institute for Scientific Information database, which dates back to 1955 for science and engineering, 1956 for the social sciences, and 1975 for the humanities. The data set is large, consisting of 2.1 million patent records and 19.9 million research articles.

When Wuchty and colleagues compared the percentages of articles published by solitary and multiple authors over the past half century, they found that team science had increased in sciences and engineering, in patents, in the social sciences, and in the humanities. In 1955, for instance, only 17.5% of the articles published in the social sciences were by teams; by 2000 this number had risen to 51.5%.

Larger teams of scientists were, and continue to be, more involved in the production of knowledge in the sciences and engineering than in the social sciences. But the rate of increase in the percentage of articles published by multiple authors over the past half century is as high for the social sciences as it is for the sciences and engineering. Analyses of the mean number of authors per published article similarly reveal consistent increases in team science over the past half century.

Even if scientific teams publish more articles than individuals, is it possible that solitary scientists continue to make the most important scientific discoveries? To address this question, Wuchty and colleagues analyzed the scientific impact of articles published by solitary and multiple authors. Their results revealed that research articles and patents by teams were more highly cited than those produced by solitary individuals. This citation advantage of teams over individuals occurred in all broad research areas—in the sciences and engineering, in the social sciences, with patents, and in the humanities. Wuchty et al. further found that the citation advantage of teams increased as the mean number of team members increased.

Of course, more authors mean there are more opportunities for self-citations, which could contribute to the citation impact of multiauthored articles. Self-citations, however, have nominal impact on citation-based indices of scholarly impact (Ruscio, Seaman, D’Oriano, Stremlo, & Mahalchik, 2012), and the citation advantage of team science and the increasing citation advantage with team size are evident even when controlling for self-citations (Wuchty, Jones, & Uzzi, 2007).

Wuchty, Jones, and Uzzi (2007) also examined one other possible advantage of sole-authored science. Specifically, they tested whether a few key concepts that drive a field are more likely to be generated by the solitary genius than by teams of scientists. To do this, they limited their analyses to the authorship of articles that received exceptionally high numbers of citations. Their results indicated that a half century ago, sole-authored articles were more likely to be among this elite group, but in contemporary science, team-authored articles are more likely to have a major impact. These data suggest that the solitary geniuses of the past are now more likely to be collaborating with others in teams to address big questions in science.

Where does psychological research fit within these aggregated data? Analyses based on disaggregated data, which Wuchty et al. (2007) included in their supplementary materials, showed that over the past 50 years, the growth in team size in the social sciences was greatest in psychological science (75.1%)—a growth rate much higher than any other social science and comparable to or higher than the growth rates found for chemistry (67.6%), engineering (63.6%), and computer science (81.2%).

At least four contextual conditions have fostered the increase in collaborative, interdisciplinary science in psychology. First, the 20th century saw a growth and maturation of psychological science and related disciplines to the point that they now provide a solid base from which to launch successful interdisciplinary expeditions. The fact that psychology is now a hub science means that the influence of psychological research extends beyond its disciplinary borders, making interdisciplinary expeditions more valuable than before psychology became a hub science. Second, as the complexity of psychological questions increased—questions that often exceeded the expertise of individual investigators—multidisciplinary and interdisciplinary collaborations were needed to provide the requisite scientific expertise. Third, advances in mathematical tools for dealing with large and complex data structures have also helped the psychological sciences connect with other disciplines. Finally, the development of new and powerful methods and measurement tools (e.g., functional magnetic resonance imaging, biomarkers, genetics, high-performance computing platforms, cross-cultural population-based surveys) has promoted productive interdisciplinary research across the neurosciences, cognitive sciences, behavioral sciences, and social sciences.

Comprehensive understandings of the mind and behavior now require that researchers use a combination of perspectives. Consequently, many of the most exciting advances in psychology today are emerging at the intersections—intersections across traditional training areas within psychology and intersections across disciplines. Cognitive neuroscience, behavioral genetics, positive psychology, social neuroscience, and health psychology are illustrative. The centrifugal forces that not long ago threatened to splinter psychology appear to be receding in the face of new centripetal force fueled by the search for more comprehensive theories.

Once again, the emergence of interdisciplinary research in psychology has implications for how we view our discipline and how we teach our introductory psychology courses. No longer simply a collection of independent subspecialties based on historical or administrative distinctions, psychology in the 21st century is becoming an integrative multilevel science. Specifically, there has been a trend in the direction of partitioning the science of mind and behavior into different levels of organization, with each contributing to our understanding of human behavior. The biological perspective in psychology concerns the material substrates for the mind and behavior; the cognitive perspective emphasizes the information processing representations and operations; and the social perspective stresses the role of the presence of conspecifics, imagined or real, and of the sociocultural context.

Additionally, there are various cross-cutting perspectives that offer invaluable insights into the mind and behavior. For example, the study of the nature and influence of changes over time (e.g., growth, decay) in neural substrates, information processing representations or operations, and social influences and processes represents a developmental perspective in psychology; the investigation of the causes and consequences of failures in neural substrates, cognitive operations, and social organizations and what such failures mean for understanding the healthy system represents a clinical perspective; and attention to the variation around the central tendency to gain leverage in formulating and testing psychological theory represents an individual differences perspective. These cross-cutting vectors are illustrative rather than exhaustive, of course, as there are other cross-cutting perspectives as well.

The important point here is that each perspective has substantive implications for other perspectives in the pursuit of comprehensive psychological explanations. The in-depth study of any one of these perspectives is essential, but a comprehensive understanding of the mind and behavior will likely come from an integration of what we know and what we can learn across multiple disciplines and perspectives.

The Neurosciences

A third major development in the 21st century is the emergence of the neurosciences in psychology. Neuroscience refers to the collection of disciplines concerned with the structure and function of the nervous system and brain. The topic of study is so complex that it requires disparate basic, clinical, and applied disciplines to cover the full terrain. Within neuroscience are cross-cutting paradigms—general perspectives that underlie a range of theories and methodological approaches.

The fulcrum for some of these perspectives rests squarely under constituent structures at different levels of organization, such as molecular neuroscience and cellular neuroscience; for others, the fulcrum falls under the function of the brain and nervous system. The brain is sufficiently complex that we will not understand brain function by drilling further and further down to molecular processes. We need also to understand the functional organization of the brain—and that is something that requires a clear understanding of psychological science.

In behavioral neuroscience, researchers view the nervous system and brain as instruments of sensation and response. Research representing this perspective tends to focus on topics such as learning, memory, motivation, homeostasis, sleep and biological rhythms, and reproduction—and on the neural mechanisms underlying these behavioral functions.

Cognitive neuroscience emerged as a distinct functional perspective in which researchers view the brain as an information-processing organ, with a focus on topics such as attention, perception, representations, decision making, memory systems, heuristics, reasoning, and executive functioning—and on the neural mechanisms in the human brain that underlie these representations and processes.

Social neuroscience represents yet another broad perspective. Social species, by definition, form organizations that extend beyond the individual. These organizations evolved hand in hand with behavioral, neural, hormonal, cellular, and genetic mechanisms, because the consequent social behaviors helped these organisms survive, reproduce, and care for offspring sufficiently long that they too reproduced. Thus, in social neuroscience, the emphasis is on the functions that derive from or are altered by the association or interaction of conspecifics—and on the underlying neural, hormonal, cellular, and genetic mechanisms associated with these functions.

Some view the emergence of the neuroscientific perspective in psychology as a special challenge to the discipline of psychology. Many students, journalists, and laypeople, for instance, think that because something is biological, it is innate and predetermined. It is important for our students and our public to understand that biological does not mean predetermined or invariant. For instance, behavioral and mental processes have a considerable amount of influence on one’s abilities to fight bacteria and viruses, and one’s perceptions of the social environment influence whether the genes in these immune cells are turned on or off to defend against bacteria or viruses (Cole, Hawkley, Arevalo, & Cacioppo, 2011). The reason is straightforward.

Throughout human history, bacteria and viruses that try to make us their home have threatened human survival. The bacteria-driven Black Death decimated Europe between 1346 and 1400, killing an estimated 30–60% of the population. Smallpox, measles, and influenza carried by Europeans to the Western Hemisphere killed as many as 90% of the native populations. The “Spanish flu” of 1918, which is related to contemporary bird flu strains, killed between 50 and 100 million people worldwide in a period of about 1 year (Cacioppo & Freberg, 2013).

Human beings formed groups to enhance the odds of their survival. Anyone who was socially excluded from these groups experienced a more hostile environment. Social exclusion not only separated a person from the help of others in life-threatening situations (e.g., fending off predators), but worse yet, it led to outright conflict with others, including combat. Under such hostile circumstances, socially excluded people faced a greater risk from bacterial infections than from viruses. This is because bacteria enter the body through cuts and scratches, whereas viruses are transmitted through body fluids (e.g., sneezing). Consequently, people are most likely to be exposed to viruses when they are in close, affine contact with other people. Thus, when individuals feel isolated and left to fend for themselves, they (like their excluded ancestors) face a greater threat from bacteria than from viruses. In that case, their brains generate signals that tell the genes in the immune system to gear up to protect against bacteria. In contrast, if individuals feel socially connected to others, their brains will initiate a cascade of hormonal signals that tells the genes to prepare to protect against viruses.

This is just one example of how perceptions of the social environment can impact biological processes that are important to brain, behavior, health, and survival. We could not understand these biological processes or their behavioral relevance if we focused only on biology. Rather, multiple perspectives are necessary to see how the biology of behavior is intimately related to the social context (Cacioppo et al., 2007). The same is true for many of the other psychological (e.g., cognitive, abnormal) perspectives. The important point here is that just because something is biological does not mean it is innate; it does not mean it is predetermined; and it most certainly does not mean other psychological perspectives have been rendered irrelevant. Quite to the contrary, other psychological perspectives and methods are playing an important role in explicating biological processes and brain function. This is another important point we need to impress upon our students in Introductory Psychology.

Conclusion

Contemporary psychological scientists stand on the shoulders of those who went before them. From this perch, it is now possible to see that the bounded subfields of the 20th century are related parts of the same landscape. This is a requisite step for bringing together research on related problems to address bigger questions and to develop more comprehensive scientific theories. Many of these bigger questions require larger and more interdisciplinary teams that were common in the prior century, and with their assemblage, the borders between the different fields of psychology and the boundaries between psychology and other scientific fields have changed. Whereas less than two decades ago, the future of psychology as a coherent scientific discipline was questioned, psychology has now emerged as an integrated, interdisciplinary scientific discipline.

Moreover, that the human brain is the organ of the mind is not in dispute. Nevertheless, we still know remarkably little about the brain mechanisms underlying the mind. Given the complexity of the human brain, progress in understanding the functional organization and structure of the human brain depends on sophisticated theoretical specifications of the psychological representations and processes that differentiate two or more comparison conditions. Psychological scientists, therefore, are well positioned to lead the search for brain mechanisms underlying psychological processes. Doing so constitutes an expansion of the purview of psychological science beyond a science of behavior and beyond a science of the mind to include a science of the brain. Such an expansion of the mission of psychological science has implications for the infrastructure and training needs of the discipline. Contrary to what some believe, this expansion builds on rather than threatens psychology’s earlier missions.

Because psychology is a hub science, there are more and more opportunities to advance science by working with scientists in other fields. The result is that more and more psychological scientists are taking faculty and research positions in nonpsychology departments and more psychology departments are hiring nonpsychologists. The same is true for other hub sciences, including physics and chemistry. These are not threats to our coherence or identity as a discipline; rather these are natural developments for a scientific discipline that has transitioned from being a balkanized and insular discipline to an integrative and interdisciplinary discipline.

We also have the opportunity to teach the nonmajors as well as the majors in our introductory courses about the exciting nature and advances of psychological science in the 21st century and the importance of psychological science in dealing with the big problems facing the next generation. Human behavior is central to all of the big problems facing the world today—pollution, natural resource depletion, population growth, global warming, nuclear proliferation, poverty, terrorism, social injustice, hunger, poor housing, and so on. Because humans play such an important role in each of these problems, psychological science has much to contribute to their understanding and mitigation. Both majors and nonmajors may better appreciate the relevance and importance of psychology if they recognize the important role psychological scientists have to play in interdisciplinary scientific teams addressing these big problems. Introductory Psychology is one—and perhaps the only—course in which we have the opportunity to teach our future public about the importance and impact of our scientific discipline and to show them how the various perspectives to which they will be exposed fit together to provide comprehensive accounts of the operation of mind and behavior.

Finally, the specialized focus on a single perspective in advanced psychology courses (e.g., Cognitive Psychology, Abnormal Psychology) can create the impression that psychology is a fractionated science. This fractionated view of psychology is often reinforced by the manner in which psychology is taught. For this reason, Introductory Psychology has a special role in our undergraduate curriculum because it is the only course in most psychology departments in which we can show how the various subfields fit together and how they augment one another to provide a more comprehensive understanding of the brain, mind, and behavior.