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Tuesday, October 27, 2026

Environmental psychology

From Wikipedia, the free encyclopedia

Environmental psychology is a branch of psychology that explores the relationship between humans and the external world. It examines the way in which the natural- and our built environments shape us as individuals. Environmental psychology investigates how humans change the environment and how the environment influences humans' experiences and behaviors. The field defines the term environment broadly, encompassing natural environments, social settings, built environments, learning environments, and informational environments. Another important research area within environmental psychology is the study of humans’ influences on the environment, that is, psychological factors influencing pro-environmental behavior and different ways it can be possible to encourage environmentally friendly behaviors, in order to mitigate climate change and biodiversity loss.

Environmental psychology was not fully recognized as its own field until the late 1960s when scientists began to question the tie between human behavior and our natural and built environments. Since its conception, the field has been committed to the development of a discipline that is both value oriented and problem oriented, prioritizing research aimed at solving complex environmental problems in the pursuit of individual well-being within a larger society.

When solving problems involving human-environment interactions, whether global or local, one must have a model of human nature that predicts the environmental conditions under which humans will respond well. This model can help design, manage, protect and/or restore environments that enhance reasonable behavior, predict the likely outcomes when these conditions are not met, and diagnose problem within the environment. The field develops such a model of human nature while retaining a broad and inherently multidisciplinary focus. It explores such dissimilar issues as common property resource management, wayfinding in complex settings, the effect of environmental stress on human performance, the characteristics of restorative environments, human information processing, and the promotion of durable conservation behavior. Lately, alongside the increased focus on climate change in society and the social sciences and the re-emergence of limits-to-growth concerns, there has been an increased focus on environmental sustainability issues within the field.

This multidisciplinary paradigm has not only characterized the dynamic for which environmental psychology is expected to develop, but it has also been the catalyst in attracting experts and scholars from other fields of study, aside from research psychologists. In environmental psychology, geographers, economists, landscape architects, policy-makers, sociologists, anthropologists, educators, and product developers all have discovered and participated in this field.

Although "environmental psychology" is arguably the best-known and most comprehensive description of the field, it is also known as human factors science, cognitive ergonomics, ecological psychology, ecopsychology, environment–behavior studies, and person–environment studies. Closely related fields include architectural psychology, socio-architecture, behavioral geography, environmental sociology, social ecology, and environmental design research.

Population density and economic disparities shape mental health.

History

The origins of the field can be traced to the Romantic poets, such as Wordsworth and Coleridge who drew attention to the power of nature intersecting with the significance of human interaction. Darwin pointed to the role of the environment in shaping evolution. This idea was quickly applied to human interactions with the surroundings. An extreme Victorian acceptance of this were 'environmental determinists' who insisted the physical environment and climate influenced the evolution of racial characteristics. Willy Hellpach is said to be the first to mention "environmental psychology". One of his books, Geopsyche, discusses topics such as how the sun and the moon affect human activity, the impact of extreme environments, and the effects of color and form. Among the other major scholars at the roots of environmental psychology were Jakob von Uexküll, Kurt Lewin, Egon Brunswik, and later Gerhard Kaminski and Carl Friedrich Graumann.

The end of World War II brought about a demand for guidance on the urgent building programme after the destruction of war. To provide government planning requirements many countries set up research centered around the studies on how people used space. In the U.K. the Building Research Centre studied space use in houses leading to further study around noise levels, heating, and lighting requirements in a living space. Pilkingtons, a glassmaker company, set up a daylight research unit, led by Thomas Markus to provide information on the influence of natural lighting in buildings and guidelines on daylight requirements. In the 1960s, Peter Manning further developed the study at the Pilkington Research Unit at the University of Liverpool. He studied offices and employed Brian Wells, one of the first people to obtain a Ph.D in environmental psychology.

Markus set up the Building Performance Research Unit at the University of Strathclyde in 1968, employing the psychologist David Canter, whom Wells and Manning had supervised for his Ph.D with the Pilkington Research Unit. Canter then went to the University of Surrey to set up an Environmental Psychology program in 1971 with the Department of Psychology. The head of the department was Terence Lee, who had conducted his PhD on the concept of the neighborhood under the supervision of Sir Frederick Bartlett at the University of Cambridge.

In parallel with these developments, people in the US had begun to consider the issues in environmental design. One of the first areas was the consideration of psychiatric hospitals. Psychiatrists worked with architects to take account of the experiences of patients who experience mental illness and discomfort. Robert Sommer wrote his book on 'Personal Space,' and Edward T Hall, an anthropologist, commented on how people relate to each other spatially. Amos Rapoport caused considerable interest amongst architects with his book 'House Form and Culture', showing that the form of buildings was not solely functional but had all sorts of cultural influences. The idea contributed to the emergence of 'post-modernism' architecture, which took the symbolic qualities of architecture very seriously. These early developments in the 1960s and 1970s were often seen as part of 'architectural psychology'.

When Harold Proshansky and William Ittelson set up the Environmental Psychology program at the City University of New York Graduate Center, the term Environmental Psychology replaces Architectural Psychology, the study of the ways in which people made sense of and interacted with their surroundings. When Canter established The Journal of Environmental Psychology in 1980 with Kenneth Craik a personality psychologist at the University of California at Berkeley, it became institutionalized to use the term environmental psychology. President Nixon's campaign to deal with depredations of the environment gave impetus to a change of direction in the field from aspects of buildings and making sense of cities to the broader issues of climate change and the impact of people in the global environment.

Environmental psychologists

Environmental psychologists are professionals trained to study the relationship between human behavior and the environment that surrounds them. These psychologists study any type of environment, even "built" environments, such as homes, schools, workplaces, neighbourhoods, parks, and event spaces. They study how we as humans behave and interact in the world. As of May 2020, the annual salary of an environmental psychologist is $82,180. The two sub-disciplines are conservation psychology and ecopsychology. Conservation Psychology is the study of the development of attitudes towards the environment and its preservation. Ecopsychology is similar to conservation psychology, but it focuses on the ties of environmental and societal degradation.

Orientations

Problem oriented

Environmental psychology is a direct study of the relationship between an environment and how that environment affects its inhabitants. Specific aspects of this field work by identifying a problem and through the identification of the said problem, discovering a solution. Therefore, it is necessary for environmental psychology to be problem-oriented.

One important aspect of a problem-oriented field is that by identifying problems, solutions arise from the research acquired. The solutions can aid in making society function better as a whole and create a wealth of knowledge about the inner workings of societies. Environmental psychologist Harold Proshansky discusses how the field is also "value-oriented" because of the field's commitment to bettering society through problem identification. Panyang discusses the importance of not only understanding the problem but also the necessity of a solution.

Proshansky also points out some of the problems of a problem-oriented approach for environmental psychology. First, the problems being identified must be studied under certain specifications: they must be ongoing and occurring in real life, not in a laboratory. Second, the notions about the problems must derive directly from the source – meaning they must come directly from the specific environment where the problem is occurring. The solutions and understanding of the problems cannot come from an environment that has been constructed and modeled to look like real life. Environmental psychology needs to reflect the actual society, not a society built in a laboratory setting. The difficult task of the environmental psychologist is to study problems as they are occurring in everyday life. It is hard to reject all laboratory research because laboratory experiments are where theories may be tested without damaging the actual environment or can serve as models when testing solutions. Proshansky makes this point as well, discussing the difficulty in the overall problem oriented approach. He states that it is important, however, for the environmental psychologist to utilize all aspects of research and analysis of the findings and to take into account both the general and individualized aspects of the problems.

Environmental psychology addresses environmental problems such as density and crowding, noise pollution, sub-standard living, and urban decay. Noise increases environmental stress. Although it has been found that control and predictability are the greatest factors in stressful effects of noise; context, pitch, source and habituation are also important variables. Environmental psychologists have theorized that density and crowding can also have an adverse effect on mood and may cause stress-related illness or behavior. To understand and solve environmental problems, environmental psychologists believe concepts and principles should come directly from the physical settings and problems being looked at. For example, factors that reduce feelings of crowding within buildings include:

  • Windows – particularly ones that can be opened and ones that provide a view as well as light
  • High ceilings
  • Doors to divide spaces (Baum and Davies) and provide access control
  • Room shape – square rooms feel less crowded than rectangular ones (Dresor)
  • Using partitions to create smaller, personalized spaces within an open plan office or larger work space.
  • Providing increases in cognitive control over aspects of the internal environment, such as ventilation, light, privacy, etc.
  • Conducting a cognitive appraisal of an environment and feelings of crowding in different settings. For example, one might be comfortable with crowding at a concert but not in school corridors.
  • Creating a defensible space (Calhoun)

Personal space and territory

Proxemics is known as the study of human space. It also studies the effects that population has on human behavior, communication, and social interaction. Having an area of personal territory in a public space, e.g., at the office, is a key feature of many architectural designs. Having such a 'defensible space' can reduce the negative effects of crowding in urban environments. The term, coined by John B. Calhoun in 1947, is the result of multiple environmental experiments conducted on rats. Originally beginning as an experiment to measure how many rats could be accommodated in a given space, it expanded into determining how rats, given the proper food, shelter and bedding would behave under a confined environment.

Under these circumstances, the males became aggressive, some exclusively homosexual. Others became pansexual and hypersexual, seeking every chance to mount any rat they encountered. As a result, mating behaviors were upset with an increase in infant mortalities. With parents failing to provide proper nests, thoughtlessly ditching their young and even attacking them, infant mortality rose as high as 96% in certain sections. Calhoun published the results as "Population Density and Social Pathology" in a 1962 edition of Scientific American.

Systems oriented

The systems-oriented approach to experimenting is applied to individuals or people that are a part of communities, groups, and organizations. These communities, groups, and organizations are systems in homeostasis. Homeostasis is known as the "state of steady conditions within a system." This approach particularly examines group interaction, as opposed to an individual's interaction and it emphasizes on factors of social integration. In the laboratory, experiments focus on cause and effect processes within human nature.

Interdisciplinary oriented

Environmental psychology relies on interaction with other disciplines in order to approach problems from multiple perspectives. The first discipline is the category of behavioral sciences, which include: sociology, political science, anthropology, and economics. Environmental psychology also interacts with the other interdisciplinary specialization field of psychology, which include: developmental psychology, cognitive science, industrial and organizational psychology, psychobiology, psychoanalysis, and social neuroscience. This multidisciplinary approach allows for a more comprehensive understanding of human-environment interactions. For instance, sociology provides insights into how social structures and cultural norms influence environmental behaviors, while economics helps analyze the financial incentives and barriers to sustainable practices. Cognitive science contributes to our understanding of how people perceive and process environmental information, which is crucial for developing effective environmental communication strategies.

In addition to the more scientific fields of study, environmental psychology closely connect with the build environment. For instance, the green building designs promoting well-being and urban planning initiatives encouraging social interaction. Environmental psychology works with the design field which includes: the studies of architecture, interior design, urban planning, industrial and object design, landscape architecture, and preservation. This collaboration between environmental psychology and design fields has led to innovative approaches in creating spaces that enhance human well-being and environmental sustainability. For example, research in environmental psychology has informed the design of restorative environments in healthcare settings, improving patient outcomes. Additionally, insights from the field have contributed to the development of urban spaces that encourage pro-environmental behaviors, such as recycling and energy conservation.

Space-over-time orientation

Space over time orientation highlights the importance of the past. Examining problems with the past in mind creates a better understanding of how past forces, such as social, political, and economic forces, may be of relevance to present and future problems. Time and place are also important to consider. It is important to look at time over extended periods. Physical settings change over time; they change with respect to physical properties and they change because individuals using the space change over time. Looking at these spaces over time will help monitor the changes and possibly predict future problems.

Concepts

Nature restoration

Environmental health shows the effects people have on the environment as well as the effects the environment has on people. From early studies showing that patients with a view of nature from their hospital recovered faster than patients with a window view of a brick wall, how, why, and to which extent nature has mental and physical restorative properties has been a central branch of the field. Although the positive effects of nature have been established, the theoretical underpinning of why it is restorative is still discussed. The most cited theory is the Attention Restoration Theory, which claims nature is a “soft fascination” which restores the ability to direct attention. It is said that being in nature can reduce stress. Studies show that it can reduce anger, improve mood, and even lower one's blood pressure.

Secondly, Stress reduction theory claims that because humans have evolved in nature, this type of environment is relaxing, and more adjusted to the senses. Newer theoretical work includes the Conditioned Restoration Theory, which suggests a two-step process. The first step involves associating nature with relaxation, and the second step involves retrieving the same relaxation when presented with an associated stimulus.

Place identity

For many years Harold Proshansky and his colleagues at the Graduate School and University Center of the City University of New York, explored the concept of place identity. Place identity has been traditionally defined as a 'sub-structure of the self-identity of the person consisting of broadly conceived cognitions about the physical world in which the individual lives'. These cognitions define the daily experiences of every human being. Through one's attitudes, feelings, ideas, memories, personal values and preferences toward the range and type of physical settings, they can then understand the environment they live in and their overall experience.

As a person interacts with various places and spaces, they are able to evaluate which properties in different environments fulfill his/her various needs. When a place contains components that satisfy a person biologically, socially, psychologically and/or culturally, it creates the environmental past of a person. Through 'good' or 'bad' experiences with a place, a person is then able to reflect and define their personal values, attitudes, feelings and beliefs about the physical world.

Place identity has been described as the individual's incorporation of place into the larger concept of self; a "potpourri of memories, conceptions, interpretations, ideas, and related feelings about specific physical settings, as well as types of settings".

Other theorists have been instrumental in the creation of the idea of place identity. Three humanistic geographers, Tuan (1980), Relph (1976) and Buttimer (1980), share a couple of basic assumptions. As a person lives and creates memories within a place, attachment is built and it is through one's personal connection to a place, that they gain a sense of belonging and purpose, which then gives significance and meaning to their life.

Five central functions of place-identity have been depicted: recognition, meaning, expressive-requirement, mediating change, and anxiety and defense function. Place identity becomes a cognitive "database" against which every physical setting is experienced. The activities of a person often overlap with physical settings, which then create a background for the rest of life's interactions and events. The individual is frequently unaware of the array of feelings, values or memories of a singular place and simply becomes more comfortable or uncomfortable with certain broad kinds of physical settings, or prefers specific spaces to others. In the time since the term "place identity" was introduced, the theory has been the model for identity that has dominated environmental psychology.

Place attachment

According to the book, "Place Attachment", place attachment is a "complex phenomenon that incorporates people-place bonding"  Many different perceptions of the bond between people and places have been hypothesized and studied. The most widespread terms include place attachment and sense of place. One consistent thread woven throughout most recent research on place attachment deals with the importance of the amount of time spent at a certain place (the length of association with a place). While both researchers and writers have made the case that time and experience in a place are important for deepening the meanings and emotional ties central to the person-place relationship, little in-depth research has studied these factors and their role in forging this connection.

Place attachment is defined as one's emotional or affective ties to a place, and is generally thought to be the result of a long-term connection with a certain environment. This is different from a simple aesthetic response such as saying a certain place is special because it is beautiful. For example, one can have an emotional response to a beautiful (or ugly) landscape or place, but this response may sometimes be shallow and fleeting. This distinction is one that Schroeder labeled "meaning versus preference". According to Schroeder the definition of "meaning" is "the thoughts, feelings, memories and interpretations evoked by a landscape"; whereas "preference" is "the degree of liking for one landscape compared to another". For a deeper and lasting emotional attachment to develop (Or in Schroeder's terms, for it to have meaning) an enduring relationship with a place is usually a critical factor. Chigbu carried out a rural study of place-attachment using a qualitative approach to check its impact on a community, Uturu (in Nigeria), and found that it has a direct relationship to the level of community development.

Environmental consciousness

Leanne Rivlin theorized that one way to examine an individual's environmental consciousness is to recognize how the physical place is significant, and look at the people/place relationship.

Environmental cognition (involved in human cognition) plays a crucial role in environmental perception.

All different areas of the brain engage with environmentally relevant information. Some believe that the orbitofrontal cortex integrates environmentally relevant information from many distributed areas of the brain. Due to its anterior location within the frontal cortex, the orbitofrontal cortex may make judgments about the environment, and refine the organism's "understanding" through error analysis, and other processes specific to the prefrontal cortex. But to be certain, there is no single brain area dedicated to the organism's interactions with its environment. Rather, all brain areas are dedicated to this task. One area (probably the orbitofrontal cortex) may collate the various pieces of the informational puzzle in order to develop a long term strategy of engagement with the ever-changing "environment".

Moreover, the orbitofrontal cortex may show the greatest change in blood oxygenation (BOLD level) when an organism thinks of the broad, and amorphous category referred to as "the environment". Research in this area is showing an increase in climate change related emotional experiences that are seen to be inherently adaptive. Engagement with these emotional experiences leads to a greater sense of connection with others and increased capacity to tolerate and reflect on emotions.

Because of the recent concern with the environment, environmental consciousness or awareness has come to be related to the growth and development of understanding and consciousness toward the biophysical environment and its problems.

Behavior settings

The earliest noteworthy discoveries in the field of environmental psychology can be dated back to Roger Barker who created the field of ecological psychology. Founding his research station in Oskaloosa, Kansas in 1947, his field observations expanded into the theory that social settings influence behavior. Empirical data gathered in Oskaloosa from 1947 to 1972 helped him develop the concept of the "behavior setting" to help explain the relationship between the individual and the immediate environment. This was further explored in his work with Paul Gump in the book Big School, Small School: High School Size and Student Behavior. One of the first insightful explanations on why groups tend to be less satisfying for their members as they increase in size, their studies illustrated that large schools had a similar number of behavior settings to that of small schools. This resulted in the students' ability to presume many different roles in small schools (e.g. be in the school band and the school football team) but in larger schools, there was a propensity to deliberate over their social choices.

In his book Ecological Psychology (1968), Barker stresses the importance of the town's behavior and environment as the residents' most ordinary instrument of describing their environment. "The hybrid, eco-behavioral character of behavior settings appear to present Midwest's inhabitants with no difficulty; nouns that combine milieu and standing behavior are common, e.g. oyster supper, basketball game, turkey dinner, golden gavel ceremony, cake walk, back surgery, gift exchange, livestock auction, auto repair."

Barker argued that his students should implement T-methods (psychologist as 'transducer': i.e. methods in which they studied the man in his 'natural environment') rather than O-methods (psychologist as "operators" i.e. experimental methods). Basically, Barker preferred fieldwork and direct observation rather than controlled experiments. Some of the minute-by-minute observations of Kansan children from morning to night, jotted down by young and maternal graduate students, may be the most intimate and poignant documents in social science. Barker spent his career expanding on what he called ecological psychology, identifying these behavior settings, and publishing accounts such as One Boy's Day (1952) and Midwest and Its Children (1955).

Natural environment research findings

Environmental psychology research has observed various concepts relating to humans' innate connection to natural environments which begins in early childhood. One study shows that fostering children's connectedness to nature will, in turn, create habitual pro-ecological behaviors in time. Exposure to natural environment may lead to a positive psychological well-being and form positive attitudes and behavior towards nature. Connectedness to nature has shown to be a huge contributor to predicting people's general pro-ecological and pro-social behaviors. Connectedness to nature has also been shown to benefit well-being, happiness, and general satisfaction. "Nature-deficit disorder" has recently been coined to explain the lack of connectedness to nature due to a lack of consciousness identification and nature disconnect. Further research is required to make definitive claims about the effects of connectedness to nature.

These positive mental health effects of environmental exposure and connection continue through adulthood and can be applied to work and other settings. One study found that nurses who weren't exposed to any natural elements throughout their work day would obtain a significantly lower score on scales measuring mental health, job satisfaction, and overall well-being. Additionally, the nurses who were not exposed to any natural elements were more likely to show signs of depression and anxiety than those who were exposed to natural elements throughout their work day.

Applications

Impact on the built environment

Environmental psychologists rejected the laboratory-experimental paradigm because of its simplification and skewed view of the cause-and-effect relationships of human behaviors and experiences. Environmental psychologists examine how one or more parameters produce an effect while other measures are controlled. It is impossible to manipulate real-world settings in a laboratory.

Environmental psychology is oriented towards influencing the work of design professionals (architects, engineers, interior designers, urban planners, etc.) and thereby improving the human environment.

On a civic scale, efforts toward improving pedestrian landscapes have paid off, to some extent, from the involvement of figures like Jane Jacobs and Copenhagen's Jan Gehl. One prime figure here is the late writer and researcher William H. Whyte. His still-refreshing and perceptive "City", based on his accumulated observations of skilled Manhattan pedestrians, provides steps and patterns of use in urban plazas.

The role and impact of architecture on human behavior is debated within the architectural profession. Views range from: supposing that people will adapt to new architectures and city forms; believing that architects cannot predict the impact of buildings on humans and therefore should base decisions on other factors; to those who undertake detailed precedent studies of local building types and how they are used by that society.

Environmental psychology has conquered the whole architectural genre which is concerned with retail stores and any other commercial venues that have the power to manipulate the mood and behavior of customers (e.g. stadiums, casinos, malls, and now airports). From Philip Kotler's landmark paper on Atmospherics and Alan Hirsch's "Effects of Ambient Odors on Slot-Machine Usage in a Las Vegas Casino", through the creation and management of the Gruen transfer, retail relies heavily on psychology, original research, focus groups, and direct observation. One of William Whyte's students, Paco Underhill, makes a living as a "shopping anthropologist". Most of this advanced research remains a trade secret and proprietary.

Environmental psychology is consulted thoroughly when discussing future city design. Eco-cities and eco-towns have been studied to determine the societal benefits of creating more sustainable and ecological designs. Eco-cities allow for humans to live in synch with nature and develop sustainable living techniques. The development of eco-cities requires knowledge in the interactions between "environmental, economic, political, and socio-cultural factors based on ecological principles". By increasing the focus on applying environmental psychology principles to urban planning and policy-making, we can create more livable and sustainable communities.

Emerging of Technology

As new technologies emerge, environmental psychologists research how these technologies are changing human-environment relationships. Smart home and city technologies are reshaping the human-environment relationship by creating more responsive and interactive living spaces. In many urban cities, technology was leveraged to promote sustainable behaviors, such as energy conservation and waste recycling, influencing individual daily habits. The urban design allow a living environment to be more adaptive and responsive to human behavior patterns. Smart home and city technologies open up opportunities for nudging sustainable behaviors but introduce corresponding privacy concerns. Environmental psychologists engage in research on the potential benefits, but also the risks, that these technologies have to promote well-being and environmental sustainability. As these technologies continue to evolve, they are doing far more than merely changing the environments we inhabit, they are also changing the ways in which we study and understand human-environment interactions.

Organizations

  • Project for Public Spaces (PPS) is a nonprofit organization that works to improve public spaces, particularly parks, civic centers, public markets, downtowns, and campuses. The staff of PPS is made up of individuals trained in environmental design, architecture, urban planning, urban geography, urban design, environmental psychology, landscape architecture, arts administration and information management. The organization has collaborated with many major institutions to improve the appearance and functionality of public spaces throughout the United States. In 2005, PPS co-founded The New York City Streets Renaissance, a campaign that worked to develop a new campaign model for transportation reform. This initiative implemented the transformation of excess sidewalk space in the Meatpacking District of Manhattan into public space. Also, by 2008, New York City reclaimed 49 acres (200,000 m2) of traffic lanes and parking spots away from cars and gave it back to the public as bike lanes and public plazas.
  • The Center for Human Environments at the CUNY Graduate Center is a research organization that examines the relationship between people and their physical settings. CHE has five subgroups that specialize in aiding specific populations: The Children's Environments Research Group, the Health and Society Research Group, the Housing Environments Research Group, the Public Space Research Group, and the Youth Studies Research Group.
  • The most relevant scientific groups are the International Association of People-Environment Studies (IAPS) and the Environmental Design Research Association (EDRA).
  • Urban Ecology, The Urban Ecologist, and the International Eco-City Conference were some of the first collectives to establish the idea of eco-cities and townships.

Challenges

The field saw significant research findings and a fair surge of interest in the late 1970s and early 1980s, but has seen challenges of nomenclature, obtaining objective and repeatable results, scope, and the fact that some research rests on underlying assumptions about human perception, which is not fully understood. Being an interdisciplinary field is difficult because it lacks a solid definition and purpose. It is hard for the field to fit into organizational structures. In the words of Guido Francescato, speaking in 2000, environmental psychology encompasses a "somewhat bewildering array of disparate methodologies, conceptual orientations, and interpretations... making it difficult to delineate, with any degree of precision, just what the field is all about and what might it contribute to the construction of society and the unfolding of history."

As environmental issues become increasingly urgent, environmental psychology is likely to play a more prominent role in addressing global challenges. A grand challenge in the field of environmental psychology today is to understand the impact of human behavior on the climate and climate change. Understanding why some people engage in pro-environment behaviors can help predict the necessary requirements to engage others in making sustainable change.

Environmental psychology has not received nearly enough supporters to be considered an interdisciplinary field within psychology. Harold M. Proshansky was one of the founders of environmental psychology and was quoted as saying "As I look at the field of environmental psychology today, I am concerned about its future. It has not, since its emergence in the early 1960s grown to the point where it can match the fields of social, personality, learning or cognitive psychology. To be sure, it has increased in membership, in the number of journals devoted to it, and even in the amount of professional organizational support it enjoys, but not enough so that one could look at any major university and find it to be a field of specialization in a department of psychology, or, more importantly, in an interdisciplinary center or institute".

University courses

  • University of Groningen offers a graduate program in environmental psychology focusing on the interactions between people and their environment. The program is taught by the world-leading Environmental Psychology group at the University of Groningen.
  • University of Victoria offers general and advanced undergraduate courses in environmental psychology, and graduate courses in Psychology and Nature, as well as Environmental Psychology of the Built Environment. The psychology graduate department also offers individualized master's and PhD programs in Environmental Psychology under the supervision of Dr. Robert Gifford.
  • Antioch University New England Graduate School offers graduate programs involving environmental education through a planning approach. With environmental psychology being such a diverse field with many different approaches, students have a variety of programs to choose from.
  • Arizona State University offers a master's in Environmental Resources, which takes more of a planning approach to the field.
  • The Environmental Psychology Ph.D program at the CUNY Graduate Center takes a multidisciplinary approach to examining and changing "the serious problems associated with the urban environment with a view towards affecting public policy" using social science theory and research methods. The GC-CUNY was the first academic institution in the U.S. to grant a Ph.D. in Environmental Psychology. As discussed in detail on the program website, "recent research has addressed the experiences of recently housed homeless people, the privatization of public space, socio-spatial conflicts, children's safety in the public environment, relocation, community based approaches to housing, the design of specialized environments such as museums, zoos, gardens and hospitals, the changing relationships between home, family and work, the environmental experiences of gay men and lesbians, and access to parks and other urban 'green spaces'." See also The Center for Human Environments.
  • Cornell University's department of Design and Environmental Analysis offers undergraduate and graduate (Master of Science in Human Environment Relations, Master of Arts in Design, and Ph.D in Human Behavior and Design) studies in environmental psychology, interior design, sustainable design studies, human factors and ergonomics, and facility planning and management.
  • Drexel University offers a Master of Science degree in Design Research. Of two degree paths, the Environmental Design and Health path includes study with community practitioners and researchers in design and related fields, including health, community design, and public policy. Research typically includes data collection and engaged research practices of design thinking and participatory design. This area of investigation has the potential to create innovative health and educational partnerships, economic opportunities and neighborhood initiatives and relates to the strategic mission of the university to be highly engaged in civic sustainability.
  • Inland Norway University of Applied Sciences offers a Masters in Environmental psychology. The focus is on how people are affected by both physical and virtual environments, as well as how people affect nature. The program offers courses on environmental behaviour, environment and neuroscience, human factors, virtual environments and cognitive design, change management and greening organizations and architecture and aesthetics.
  • The Ohio State University City & Regional Planning Program, in the School of Architecture, offers a specialization in environmental psychology (urban design/physical planning and behavior) at both the master's and PhD level. Dissertations have examined such topics as environmental aesthetics, spatial cognition, ethnic enclaves, neighborhood decline, neighborhood satisfaction, restorative and livable places, and behavior change.
  • Prescott College offers a master's program that incorporates a number of the foundations of environmental psychology as well. The sub-fields in which the program provides includes environmental education, environmental studies, ecology, botany, resource policy, and planning.
  • University of California, Irvine offers a doctoral specialization in Design & Behavior Research within the Department of Planning, Policy, and Design in the School of Social Ecology, and undergraduate coursework in Environmental Psychology offered jointly by the Departments of Psychology and Social Behavior, Planning, Policy, and Design, and the Program in Public Health.
  • The University of Michigan offers Master of Science and Master of Arts degrees in its new School for Sustainability and Environment (SEAS). The focus is on how people affect and are affected by environments, and includes a pragmatic approach to promoting environmental stewardship behavior, as well as a focus on how "nearby nature" affects people's mental vitality, physical health and well-being. An emerging theme is helping people to remain optimistic while learning to respond well to increasingly difficult biophysical circumstances.
  • Another strain of environmental psychology developed out of ergonomics in the 1960s. The beginning of this movement can be traced back to David Canter's work and the founding of the "Performance Research Unit" at the University of Strathclyde in Glasgow, Scotland, in 1966, which expanded traditional ergonomics to study broader issues relating to the environment and the extent to which human beings were "situated" within it (cf situated cognition). Canter led the field in the UK for years and was the editor of the Journal of Environmental Psychology for over 20 years, but has recently turned his attention to criminology.
  • The University of Surrey was the first institution that offered an architectural psychology course in the UK starting in 1973. Since then, there have been over 250 graduates from over 25 countries. The Environmental Psychology Research Group (EPRG) within the University of Surrey, of which students on the M.Sc in Environmental Psychology are automatically members, has been undertaking research for more than thirty years. EPRG's mission is to gain a better understanding of the environmental and psychological effects of space, no matter the size, with help from social sciences, psychology, and methodologies. There are four categories under which the research projects fall: sustainable development, environmental risk, architectural assessment and environmental design, and environmental education and interpretation. Other universities in the UK now offer courses on the subject, which is an expanding field.

See the APA's list of additional environmental psychology graduate programs here: http://www.apadivisions.org/division-34/about/resources/graduate-programs.aspx

Academic and professional bodies

The main academic and professional organizations for the discipline of Environmental Psychology are Division 34: Society for Environmental, Population, & Conservation Psychology of the American Psychological Association (APA), the International Association of People-Environment Studies (IAPS), Division 4: Environmental Psychology of the International Association of Applied Psychology (IAAP), the Environmental Psychology Section of the German Psychological Society (DGPs), and the Environmental Psychology Section of the British Psychological Society.

Academic journals

There are several peer-reviewed psychological journals that publish academic work on environmental psychology: Journal of Environmental Psychology, Environment and Behavior, Umweltpsychologie, Global Environmental Psychology, Current Research in Ecological and Social Psychology, Frontiers in Psychology: Section for Environmental Psychology.

Academic work also appears in interdisciplinary journals that have a broad thematic focus: Global Environmental Change, Journal of Environmental Communication, Energy Research & Social Science, Nature Climate Change, Nature Human Behaviour, or PLOS One.

Journals in the related field of Ecopsychology may also publish environmental psychological research. These journals include Ecological Psychology (journal), PsyEcology, Journal of Ecopsychology, and European Journal of Ecopsychology.

Positive feedback

From Wikipedia, the free encyclopedia
Causal loop diagram that depicts the causes of a stampede as a positive feedback loop. Alarm or panic can sometimes be spread by positive feedback among a herd of animals to cause a stampede.

Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop where the outcome of a process reinforces the inciting process to build momentum. As such, these forces can exacerbate the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A. In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback. Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics.

Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. That is, positive feedback is in phase with the input, in the sense that it adds to make the input larger. Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations, chaotic behavior or other divergences from equilibrium. System parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state. Positive feedback may be controlled by signals in the system being filtered, damped, or limited, or it can be cancelled or reduced by adding negative feedback.

Positive feedback is used in digital electronics to force voltages away from intermediate voltages into '0' and '1' states. On the other hand, thermal runaway is a type of positive feedback that can destroy semiconductor junctions. Positive feedback in chemical reactions can increase the rate of reactions, and in some cases can lead to explosions. Positive feedback in mechanical design causes tipping-point, or over-centre, mechanisms to snap into position, for example, in switches and locking pliers. Out of control, it can cause bridges to collapse. Positive feedback in economic systems can cause boom-then-bust cycles. A familiar example of positive feedback is the loud squealing or howling sound produced by audio feedback in public address systems: the microphone picks up sound from its own loudspeakers, amplifies it, and sends it through the speakers again.

Overview

Positive feedback enhances or amplifies an effect by it having an influence on the process that gave rise to it. For example, when part of an electronic output signal returns to the input, and is in phase with it, the system gain is increased. The feedback from the outcome to the originating process can be direct, or it can be via other state variables. Such systems can give rich qualitative behaviors, but whether the feedback is instantaneously positive or negative in sign has an extremely important influence on the results. Positive feedback reinforces and negative feedback moderates the original process. Positive and negative in this sense refer to loop gains greater than or less than zero, and do not imply any value judgements as to the desirability of the outcomes or effects. A key feature of positive feedback is thus that small disturbances get bigger. When a change occurs in a system, positive feedback causes further change in the same direction.

Basic

A basic feedback system can be represented by this block diagram. In the diagram the + symbol is an adder and A and B are arbitrary causal functions.

A simple feedback loop is shown in the diagram. If the loop gain AB is positive, then a condition of positive or regenerative feedback exists.

If the functions A and B are linear and AB is smaller than unity, then the overall system gain from the input to output is finite but can be very large as AB approaches unity. In that case, it can be shown that the overall or loop gain from input to output is:

When AB > 1, the system is unstable, so does not have a well-defined gain; the gain may be called infinite.

Thus, depending on the feedback, state changes can be convergent or divergent. The result of positive feedback is to augment changes, so that small perturbations may result in big changes.

A system in equilibrium in which there is positive feedback to any change from its current state may be unstable, in which case the system is said to be in an unstable equilibrium. The magnitude of the forces that act to move such a system away from its equilibrium is an increasing function of the distance of the state from the equilibrium.

Positive feedback does not necessarily imply instability of an equilibrium; for example, stable on and off states may exist in positive-feedback architectures.

Hysteresis

Hysteresis causes the output value to depend on the history of the input.
In a Schmitt trigger circuit, feedback to the non-inverting input of an amplifier pushes the output directly away from the applied voltage towards the maximum or minimum voltage the amplifier can generate.

In the real world, positive feedback loops typically do not cause ever-increasing growth but are modified by limiting effects of some sort. According to Donella Meadows:

"Positive feedback loops are sources of growth, explosion, erosion, and collapse in systems. A system with an unchecked positive loop ultimately will destroy itself. That's why there are so few of them. Usually, a negative loop will kick in sooner or later."

Hysteresis, in which the starting point affects where the system ends up, can be generated by positive feedback. When the gain of the feedback loop is above 1, then the output moves away from the input: if it is above the input, then it moves towards the nearest positive limit, while if it is below the input then it moves towards the nearest negative limit.

Once it reaches the limit, it will be stable. However, if the input goes past the limit, then the feedback will change sign and the output will move in the opposite direction until it hits the opposite limit. The system therefore shows bistable behaviour.

Terminology

The terms positive and negative were first applied to feedback before World War II. The idea of positive feedback was already current in the 1920s with the introduction of the regenerative circuit.

Friis & Jensen (1924) described regeneration in a set of electronic amplifiers as a case where the "feed-back" action is positive in contrast to negative feed-back action, which they mention only in passing. Harold Stephen Black's classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:

"Positive feed-back increases the gain of the amplifier, negative feedback reduces it."

According to Mindell (2002) confusion in the terms arose shortly after this:

"...Friis and Jensen had made the same distinction Black used between 'positive feed-back' and 'negative feed-back', based not on the sign of the feedback itself but rather on its effect on the amplifier's gain. In contrast, Nyquist and Bode, when they built on Black's work, referred to negative feedback as that with the sign reversed. Black had trouble convincing others of the utility of his invention in part because confusion existed over basic matters of definition."

These confusions, along with the everyday associations of positive with good and negative with bad, have led many systems theorists to propose alternative terms. For example, Donella Meadows prefers the terms reinforcing and balancing feedbacks.

Examples and applications

In electronics

A vintage style regenerative radio receiver. Due to the controlled use of positive feedback, sufficient amplification can be derived from a single vacuum tube or valve (centre).

Regenerative circuits were invented and patented in 1914 for the amplification and reception of very weak radio signals. Carefully controlled positive feedback around a single transistor amplifier can multiply its gain by 1,000 or more. Therefore, a signal can be amplified 20,000 or even 100,000 times in one stage, which would normally have a gain of only 20 to 50. The problem with regenerative amplifiers working at these very high gains is that they easily become unstable and start to oscillate. The radio operator has to be prepared to tweak the amount of feedback fairly continuously for good reception. Superregenerative receivers use even more gain. Modern radio receivers use the superheterodyne design, with many more amplification stages, but much more stable operation and no positive feedback.

The oscillation that can break out in a regenerative radio circuit is used in electronic oscillators. By the use of tuned circuits or a piezoelectric crystal (commonly quartz), the signal that is amplified by the positive feedback remains linear and sinusoidal. There are several designs for such harmonic oscillators, including the Armstrong oscillator, Hartley oscillator, Colpitts oscillator, and the Wien bridge oscillator. They all use positive feedback to create oscillations.

Many electronic circuits, especially amplifiers, incorporate negative feedback. This reduces their gain, but improves their linearity, input impedance, output impedance, and bandwidth, and stabilises all of these parameters, including the loop gain. These parameters also become less dependent on the details of the amplifying device itself, and more dependent on the feedback components, which are less likely to vary with manufacturing tolerance, age and temperature. The difference between positive and negative feedback for AC signals is one of phase: if the signal is fed back out of phase, the feedback is negative, and if it is in phase, the feedback is positive. One problem for amplifier designers who use negative feedback is that some of the components of the circuit will introduce phase shift in the feedback path. If there is a frequency (usually a high frequency) where the phase shift reaches 180°, then the designer must ensure that the amplifier gain at that frequency is very low (usually by low-pass filtering). If the loop gain (the product of the amplifier gain and the extent of the positive feedback) at any frequency is greater than one, then the amplifier will oscillate at that frequency (Barkhausen stability criterion). Such oscillations are sometimes called parasitic oscillations. An amplifier that is stable in one set of conditions can break into parasitic oscillation in another. This may be due to changes in temperature, supply voltage, adjustment of front-panel controls, or even the proximity of a person or other conductive item.

Amplifiers may oscillate gently in ways that are hard to detect without an oscilloscope, or the oscillations may be so extensive that only a very distorted or no required signal at all gets through, or that damage occurs. Low-frequency parasitic oscillations have been called 'motorboating' due to the similarity to the sound of a low-revving exhaust note.

The effect of using a Schmitt trigger (B) instead of a comparator (A)

Many common digital electronic circuits employ positive feedback. While normal, simple logic gates usually rely simply on gain to push digital signal voltages away from intermediate values to the values that are meant to represent Boolean 0 and 1, but many more complex gates use feedback. When an input voltage is expected to vary in an analogue way, but sharp thresholds are required for later digital processing, the Schmitt trigger circuit uses positive feedback to ensure that if the input voltage creeps gently above the threshold, the output is forced smartly and rapidly from one logic state to the other. One of the corollaries of the Schmitt trigger's use of positive feedback is that, should the input voltage move gently down again past the same threshold, the positive feedback will hold the output in the same state with no change. This effect is called hysteresis: the input voltage has to drop past a different, lower threshold to 'un-latch' the output and reset it to its original digital value. By reducing the extent of the positive feedback, the hysteresis width can be reduced, but it can not entirely be eradicated. The Schmitt trigger is, to some extent, a latching circuit.

Positive feedback is a mechanism by which an output, such as protein levels, is enhanced. However, in order to avoid any fluctuation in the protein level, the mechanism is inhibited stochastically (I); therefore, when the concentration of the activated protein (A) is past the threshold ([I]), the loop mechanism is activated and the concentration of A increases exponentially if d[A]=k [A].
Illustration of an R-S ('reset-set') flip-flop made from two digital nor gates with positive feedback. Red and black mean logical '1' and '0', respectively.

An electronic flip-flop, or "latch", or "bistable multivibrator", is a circuit that, due to high positive feedback, is not stable in a balanced or intermediate state. Such a bistable circuit is the basis of one bit of electronic memory. The flip-flop uses a pair of amplifiers, transistors, or logic gates connected to each other so that positive feedback maintains the state of the circuit in one of two unbalanced stable states after the input signal has been removed until a suitable alternative signal is applied to change the state. Computer random access memory (RAM) can be made in this way, with one latching circuit for each bit of memory.

Thermal runaway occurs in electronic systems because some aspect of a circuit is allowed to pass more current when it gets hotter, then the hotter it gets, the more current it passes, which heats it some more and so it passes yet more current. The effects are usually catastrophic for the device in question. If devices have to be used near their maximum power-handling capacity, and thermal runaway is possible or likely under certain conditions, improvements can usually be achieved by careful design.

A phonograph turntable is prone to acoustic feedback.

Audio and video systems can demonstrate positive feedback. If a microphone picks up the amplified sound output of loudspeakers in the same circuit, then howling and screeching sounds of audio feedback (at up to the maximum power capacity of the amplifier) will be heard, as random noise is re-amplified by positive feedback and filtered by the characteristics of the audio system and the room.

Audio and live music

Audio feedback (also known as acoustic feedback, simply as feedback, or the Larsen effect) is a special kind of positive feedback which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a loudly-amplified loudspeaker). In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting sound is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them. For small PA systems the sound is readily recognized as a loud squeal or screech.

Feedback is almost always considered undesirable when it occurs with a singer's or public speaker's microphone at an event using a sound reinforcement system or PA system. Audio engineers use various electronic devices, such as equalizers and, since the 1990s, automatic feedback detection devices to prevent these unwanted squeals or screeching sounds, which detract from the audience's enjoyment of the event. On the other hand, since the 1960s, electric guitar players in rock music bands using loud guitar amplifiers and distortion effects have intentionally created guitar feedback to create a desirable musical effect. "I Feel Fine" by the Beatles marks one of the earliest examples of the use of feedback as a recording effect in popular music. It starts with a single, percussive feedback note produced by plucking the A string on Lennon's guitar. Artists such as the Kinks and the Who had already used feedback live, but Lennon remained proud of the fact that the Beatles were perhaps the first group to deliberately put it on vinyl. In one of his last interviews, he said, "I defy anybody to find a record—unless it's some old blues record in 1922—that uses feedback that way."

The principles of audio feedback were first discovered by Danish scientist Søren Absalon Larsen. Microphones are not the only transducers subject to this effect. Phone cartridges can do the same, usually in the low-frequency range below about 100 Hz, manifesting as a low rumble. Jimi Hendrix was an innovator in the intentional use of guitar feedback in his guitar solos to create unique sound effects. He helped develop the controlled and musical use of audio feedback in electric guitar playing, and later Brian May was a famous proponent of the technique.

Video

Video feedback

Similarly, if a video camera is pointed at a monitor screen that is displaying the camera's own signal, then repeating patterns can be formed on the screen by positive feedback. This video feedback effect was used in the opening sequences to the first ten seasons of the television program Doctor Who.

Switches

In electrical switches, including bimetallic strip based thermostats, the switch usually has hysteresis in the switching action. In these cases hysteresis is mechanically achieved via positive feedback within a tipping point mechanism. The positive feedback action minimises the length of time arcing occurs for during the switching and also holds the contacts in an open or closed state.

In biology

In physiology

Positive feedback is the amplification of a body's response to a stimulus. For example, in childbirth, when the head of the fetus pushes up against the cervix (1) it stimulates a nerve impulse from the cervix to the brain (2). When the brain is notified, it signals the pituitary gland to release a hormone called oxytocin(3). Oxytocin is then carried via the bloodstream to the uterus (4), causing contractions, pushing the fetus towards the cervix, eventually inducing childbirth.
Platelet clotting demonstrates positive feedback. The damaged blood vessel wall releases chemicals that initiate the formation of a blood clot through platelet congregation. As more platelets gather, more chemicals are released that speed up the process. The process gets faster and faster until the blood vessel wall is completely sealed and the positive feedback loop has ended. The exponential form of the graph illustrates the positive feedback mechanism.

A number of examples of positive feedback systems may be found in physiology.

  • One example is the onset of contractions in childbirth, known as the Ferguson reflex. When a contraction occurs, the hormone oxytocin causes a nerve stimulus, which stimulates the hypothalamus to produce more oxytocin, which increases uterine contractions. This results in contractions increasing in amplitude and frequency.
  • Another example is the process of blood clotting. The loop is initiated when injured tissue releases signal chemicals that activate platelets in the blood. An activated platelet releases chemicals to activate more platelets, causing a rapid cascade and the formation of a blood clot.
  • Lactation also involves positive feedback in that as the baby suckles on the nipple, there is a nerve response into the spinal cord and up into the hypothalamus of the brain, which then stimulates the pituitary gland to produce more prolactin to produce more milk.
  • A spike in estrogen during the follicular phase of the menstrual cycle causes ovulation.
  • The generation of nerve signals is another example, in which the membrane of a nerve fibre causes slight leakage of sodium ions through sodium channels, resulting in a change in the membrane potential, which in turn causes more opening of channels, and so on (Hodgkin cycle). So a slight initial leakage results in an explosion of sodium leakage, which creates the nerve action potential.
  • In excitation–contraction coupling of the heart, an increase in intracellular calcium ions to the cardiac myocyte is detected by ryanodine receptors in the membrane of the sarcoplasmic reticulum, which transport calcium out into the cytosol in a positive feedback physiological response.

In most cases, such feedback loops culminate in counter-signals being released that suppress or break the loop. Childbirth contractions stop when the baby is out of the mother's body. Chemicals break down the blood clot. Lactation stops when the baby no longer nurses.

In gene regulation

Positive feedback is a well-studied phenomenon in gene regulation, where it is most often associated with bistability. Positive feedback occurs when a gene activates itself directly or indirectly via a double negative feedback loop. Genetic engineers have constructed and tested simple positive feedback networks in bacteria to demonstrate the concept of bistability. A classic example of positive feedback is the lac operon in E. coli. Positive feedback plays an integral role in cellular differentiation, development, and cancer progression, and therefore, positive feedback in gene regulation can have significant physiological consequences. Random motions in molecular dynamics coupled with positive feedback can trigger interesting effects, such as creating a population of phenotypically different cells from the same parent cell. This happens because noise can become amplified by positive feedback. Positive feedback can also occur in other forms of cell signaling, such as enzyme kinetics or metabolic pathways.

In evolutionary biology

Positive feedback loops have been used to describe aspects of the dynamics of change in biological evolution. For example, beginning at the macro level, Alfred J. Lotka (1945) argued that the evolution of the species was most essentially a matter of selection that fed back energy flows to capture more and more energy for use by living systems. At the human level, Richard D. Alexander (1989) proposed that social competition between and within human groups fed back to the selection of intelligence, thus constantly producing more and more refined human intelligence. Crespi (2004) discussed several other examples of positive feedback loops in evolution. The analogy of evolutionary arms races provides further examples of positive feedback in biological systems.

During the Phanerozoic, the biodiversity shows a steady but not monotonic increase from near zero to several thousands of genera.

It has been shown that changes in biodiversity through the Phanerozoic correlate much better with hyperbolic model (widely used in demography and macrosociology) than with exponential and logistic models (traditionally used in population biology and extensively applied to fossil biodiversity as well). The latter models imply that changes in diversity are guided by first-order positive feedback (more ancestors, more descendants) or a negative feedback arising from resource limitation. The hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the world population growth has been demonstrated (see below) to arise from second-order positive feedback between the population size and the rate of technological growth. The hyperbolic character of biodiversity growth can be similarly accounted for by a positive feedback between the diversity and community structure complexity. It has been suggested that the similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the interference of the hyperbolic trend (produced by the positive feedback) with cyclical and stochastic dynamics.

Immune system

A cytokine storm, or hypercytokinemia is a potentially fatal immune reaction consisting of a positive feedback loop between cytokines and immune cells, with highly elevated levels of various cytokines. In normal immune function, positive feedback loops can be utilized to enhance the action of B lymphocytes. When a B cell binds its antibodies to an antigen and becomes activated, it begins releasing antibodies and secreting a complement protein called C3. Both C3 and a B cell's antibodies can bind to a pathogen, and when a B cell has its antibodies bind to a pathogen with C3, it speeds up that B cell's secretion of more antibodies and more C3, thus creating a positive feedback loop.

Cell death

Apoptosis is a caspase-mediated process of cellular death, whose aim is the removal of long-lived or damaged cells. A failure of this process has been implicated in prominent conditions such as cancer or Parkinson's disease. The very core of the apoptotic process is the auto-activation of caspases, which may be modelled via a positive-feedback loop. This positive feedback exerts an auto-activation of the effector caspase by means of intermediate caspases. When isolated from the rest of the apoptotic pathway, this positive feedback presents only one stable steady state, regardless of the number of intermediate activation steps of the effector caspase. When this core process is complemented with inhibitors and enhancers of caspase effects, this process presents bistability, thereby modelling the alive and dying states of a cell.

In psychology

Winner (1996) described gifted children as driven by positive feedback loops involving setting their own learning course, this feeding back satisfaction, thus further setting their learning goals to higher levels and so on. Winner termed this positive feedback loop as a rage to master. Vandervert (2009a, 2009b) proposed that the child prodigy can be explained in terms of a positive feedback loop between the output of thinking/performing in working memory, which then is fed to the cerebellum where it is streamlined, and then fed back to working memory thus steadily increasing the quantitative and qualitative output of working memory. Vandervert also argued that this working memory/cerebellar positive feedback loop was responsible for language evolution in working memory.

In economics

Markets with social influence

Product recommendations and information about past purchases have been shown to influence consumers' choices significantly, whether it is for music, movies, books, technological, and other types of products. Social influence often induces a rich-get-richer phenomenon (Matthew effect) where popular products tend to become even more popular.

Market dynamics

According to the theory of reflexivity advanced by George Soros, price changes are driven by a positive feedback process whereby investors' expectations are influenced by price movements so their behaviour acts to reinforce movement in that direction until it becomes unsustainable, whereupon the feedback drives prices in the opposite direction.

In social media

Programs such as Facebook and Twitter depend on positive feedback to create interest in topics and drive the take-up of the media. In the age of smartphones and social media, the feedback loop has created a craze for virtual validation in the form of likes, shares, and FOMO (fear of missing out). This is intensified by the use of bots which are designed to respond to particular words or themes and transmit posts more widely.

What is called negative feedback in social media should often be regarded as positive feedback in this context. Outrageous statements and negative comments often produce much more feedback than positive comments.

Systemic risk

Systemic risk is the risk that an amplification or leverage or positive feedback process presents to a system. This is usually unknown, and under certain conditions, this process can amplify exponentially and rapidly lead to destructive or chaotic behaviour. A Ponzi scheme is a good example of a positive-feedback system: funds from new investors are used to pay out unusually high returns, which in turn attract more new investors, causing rapid growth toward collapse. W. Brian Arthur has also studied and written on positive feedback in the economy (e.g. W. Brian Arthur, 1990). Hyman Minsky proposed a theory that certain credit expansion practices could make a market economy into "a deviation amplifying system" that could suddenly collapse, sometimes called a Minsky moment.

Simple systems that clearly separate the inputs from the outputs are not prone to systemic risk. This risk is more likely as the complexity of the system increases because it becomes more difficult to see or analyze all the possible combinations of variables in the system even under careful stress testing conditions. The more efficient a complex system is, the more likely it is to be prone to systemic risks because it takes only a small amount of deviation to disrupt the system. Therefore, well-designed complex systems generally have built-in features to avoid this condition, such as a small amount of friction, or resistance, or inertia, or time delay to decouple the outputs from the inputs within the system. These factors amount to an inefficiency, but they are necessary to avoid instabilities.

The 2010 Flash Crash incident was blamed on the practice of high-frequency trading (HFT), although whether HFT really increases systemic risk remains controversial.[citation needed]

Human population growth

Agriculture and human population can be considered to be in a positive feedback mode, which means that one drives the other with increasing intensity. It is suggested that this positive feedback system will end sometime with a catastrophe, as modern agriculture is using up all of the easily available phosphate and is resorting to highly efficient monocultures, which are more susceptible to systemic risk.

Technological innovation and human population can be similarly considered, and this has been offered as an explanation for the apparent hyperbolic growth of the human population in the past, instead of a simpler exponential growth. It is proposed that the growth rate is accelerating because of second-order positive feedback between population and technology. Technological growth increases the carrying capacity of land for people, which leads to a growing population, and this in turn drives further technological growth.

Prejudice, social institutions and poverty

Gunnar Myrdal described a vicious circle of increasing inequalities and poverty, which is known as circular cumulative causation.

James Moody, Assistant Professor at Ohio State University, states that students who self-segregate or grow up in segregated environments have "little meaningful exposure to other races because they never form relationships with students of another race...[; as a result,...] they are viewing other racial groups at a social distance, which can bolster stereotypes," which ultimately causes a positive feedback loop in which segregated groups become more prejudiced, polarized, and segregated against each other, similar to that of political polarization.

In meteorology

Drought intensifies through positive feedback. A lack of rain decreases soil moisture, which kills plants or causes them to release less water through transpiration. Both factors limit evapotranspiration, the process by which water vapour is added to the atmosphere from the surface, and add dry dust to the atmosphere, which absorbs water. Less water vapour means both low dew point temperatures and more efficient daytime heating, decreasing the chances of humidity in the atmosphere leading to cloud formation. Lastly, without clouds, there cannot be rain, and the loop is complete.

In climatology

Human-caused increases in greenhouse gases stimulate positive feedback in global warming.
 
Some effects of global warming can either enhance (positive feedbacks) or inhibit (negative feedbacks) warming.
 
Globally, wildfires and deforestation have reduced forests' net absorption of greenhouse gases, reducing their effectiveness at mitigating climate change. Global warming increases forest fires that release more greenhouse gases, creating a positive feedback loop that causes more warming.
 
Over recent decades, "forest disturbance" (damage) by fire has increased in most of the planet's forest zones. The increase in area, frequency, and severity of forest fires creates a positive feedback that increases global warming.

Climate forcings may push a climate system in the direction of warming or cooling, for example, increased atmospheric concentrations of greenhouse gases cause warming at the surface. Forcings are external to the climate system and feedbacks are internal processes of the system. Some feedback mechanisms act in relative isolation to the rest of the climate system while others are tightly coupled. Forcings, feedbacks and the dynamics of the climate system determine how much and how fast the climate changes. The main positive feedback in global warming is the tendency of warming to increase the amount of water vapour in the atmosphere, which in turn leads to further warming. The main negative feedback comes from the Stefan–Boltzmann law, the amount of heat radiated from the Earth into space is proportional to the fourth power of the temperature of Earth's surface and atmosphere.

Other examples of positive feedback subsystems in climatology include:

  • A warmer atmosphere melts ice, changing the albedo (surface reflectivity), which further warms the atmosphere.
  • Methane hydrates can be unstable so that a warming ocean could release more methane, which is also a greenhouse gas.
  • Peat, occurring naturally in peat bogs, contains carbon. When peat dries it decomposes, and may additionally burn. Peat also releases nitrous oxide.
  • Global warming affects the cloud distribution. Clouds at higher altitudes enhance the greenhouse effect, while low clouds mainly reflect back sunlight, having opposite effects on temperature.

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report states that "Anthropogenic warming could lead to some effects that are abrupt or irreversible, depending upon the rate and magnitude of the climate change."

In sociology

In sociology a network effect can quickly create the positive feedback of a bank run. The above photo is of the UK Northern Rock 2007 bank run.

A self-fulfilling prophecy is a social positive feedback loop between beliefs and behaviour: if enough people believe that something is true, their behaviour can make it true, and observations of their behaviour may in turn increase belief. A classic example is a bank run.

Another sociological example of positive feedback is the network effect. When more people are encouraged to join a network, this increases the reach of the network, therefore the network expands ever more quickly. A viral video is an example of the network effect in which links to a popular video are shared and redistributed, ensuring that more people see the video and then re-publish the links. This is the basis for many social phenomena, including Ponzi schemes and chain letters. In many cases, population size is the limiting factor to the feedback effect.

In political science

In politics, institutions can reinforce norms, which can subsequently be a source of positive feedback. This rationale is frequently utilized to comprehend public policy processes, which may be dissected into a sequence of events. Self-reinforcing processes are understood to be affected by positive feedback mechanisms (e.g., supportive policy constituencies). Conversely, unsuccessful policy processes encounter negative feedback mechanisms (e.g., veto points with veto power).

A comparative illustration of policy feedback can be observed in the economic foreign policies of Brazil and China, particularly in their execution of state capitalism tactics during the 1990s and 2000s. Although both nations initially embraced similar state capitalist ideas, their paths in executing economic policies diverged over time due to distinct incentives. In China, a positive feedback mechanism reinforced previous policies, whereas in Brazil, negative feedback mechanisms compelled the country to abandon state capitalism policies and dynamics.

In chemistry

If a chemical reaction causes the release of heat, and the reaction itself happens faster at higher temperatures, then there is a high likelihood of positive feedback. If the heat produced is not removed from the reactants fast enough, thermal runaway can occur and very quickly lead to a chemical explosion.

In conservation

Rare plant and animal species are often particularly sought after by poachers, which in turn drives these species further to extinction and increases their rarity. This is compounded by the Allee effect, which describes how individuals within a species become less fit for survival and reproduction as their species' population declines. Even relatively moderate consumer demand or relatively low prices for plant and animal parts can quickly escalate and put a species on a trajectory toward extinction.

Environmental psychology

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