The current consensus among scientists is that a combination of genetic and environmental factors influences how people think, feel, and behave. This article examines recent research about how environmental influences can work alongside genetic influences to shape character and behavior. Ultimately, such research may yield insights that will help stakeholders design environments that optimize people's underlying character traits, thereby encouraging the desirable behaviors that arise from them.

People change their perceptions of environments on the basis of their own physical characteristics and abilities.

The physical setup of an environment can influence behavior in surprising ways. Recently, researchers from Cornell University (Ithaca, New York) and the University of New South Wales (Sydney, Australia) conducted a study to determine whether a person's environment can affect how much the person eats. The researchers set up a clean, neat kitchen and a messy, cluttered kitchen and placed snacks—carrots, cookies, and crackers—in both kitchens. During the study, the researchers told participants to enjoy the snacks and asked them to complete a writing assignment in one of the two kitchens, instructing some women to write about an instance in which they felt in control and others to write about an instance in which they felt out of control. The researchers found that "among women who wrote about feeling out of control, those in the messy kitchen tended to consume twice as many calories from cookies as women in the tidy kitchen.... In the cluttered kitchen...women who wrote about a time when they felt in control consumed fewer calories from cookies...than did the women who wrote about a time when they were out of control" ("A Cluttered Kitchen Can Nudge Us To Overeat, Study Finds," National Public Radio, 15 February 2016; online). The results of the study suggest that a person's environment and mind-set have a direct effect on eating behavior. This finding has implications for work environments, where people might encounter both messes and cheap foods that are high in calories and low in nutrients. Economic factors—particularly economic inequality—can have profound impacts on people's well-being, ability to function in society, and even calorie consumption. A recent study by researchers from the University of St Andrews (St Andrews, Scotland), Université Libre de Bruxelles (Brussels, Belgium), the University of Edinburgh (Edinburgh, Scotland), and the University of Melbourne (Parkville, Australia) found a link between the stress and anxiety economic inequality causes and excess calorie consumption that can result in obesity. And researchers from Texas Christian University (Fort Worth, Texas), the University of Arizona (Tucson, Arizona), and the University of Minnesota (Minneapolis and Saint Paul, Minnesota) conducted a study and found that people who grew up in chronic poverty had a tendency to consume calories even when they were not hungry.

Environmental factors such as diet and cohabitation with other people have a direct and significant effect on the makeup of the immune system in humans. Indeed, genetic factors appear to be responsible for only about 25% of the variation in immune systems among adults. According to study findings published by a team of researchers from the University of Cambridge (Cambridge, England), the University of Leuven (Leuven, Belgium), and other institutions, the immune systems of married couples showed an average of 50% less variation than did the immune systems of men and women with similar demographics whom the researchers paired randomly for the study. The finding that cohabiting individuals have such a significant effect on each other's immune systems could see beneficial application in the field of immunotherapy. For example, doctors may be able to use social-network analysis in the development of treatments for ailing patients.

Environments can also have profound impacts on people's personality traits; however, recent research suggests that various environmental influences play a much smaller role in shaping such traits than anyone assumed they did. A recent study by a team comprising researchers from King's College London (London, England); Goldsmiths, University of London (London, England); Tomsk State University (Tomsk, Russia); and the University of New Mexico (Albuquerque, New Mexico) used more than 2,000 pairs of twins to examine the heritability of grit—persistence of effort and continuing focus on long-term goals. The researchers focused on grit because the personality trait is a significant indicator of academic achievement. In the researchers' statistical models, family and schools (environmental influences) contributed nothing to the development of grit. The researchers used a UK standardized test to measure variability in academic achievement and found that genetics—genes' coding for various personality traits, including grit—explained two-thirds of that variability; however, the researchers are quick to point out that genetic influences are not necessarily immutable. Although the study revealed that family and schools had essentially no effect on the development of grit, other environmental influences may be capable of changing personality traits and the underlying genetics that give rise to them. In other words, the factors most responsible for academic success are the ones humans have the least control over. Parents, schools, and society as a whole may be investing heavily in activities that do not change a child's underlying personality traits and therefore do not contribute significantly to improving academic achievement.

Research by Colorado State University (Fort Collins, Colorado) cognitive psychologist Jessica Witt and colleagues shows that people change their perceptions of environments and the objects they encounter in environments on the basis of their prior experiences and their own physical characteristics and abilities. In one experiment, Dr. Witt and colleagues asked softball players who had just finished a game to choose the softball-size circle on a poster featuring several circles of various sizes. Players who batted well during the game tended to overestimate the size of the softball, and players who batted poorly tended to underestimate the size of the softball. Other experiments revealed that distances appear greater to obese people than they do to normal and only moderately overweight people and that people who are elderly, tired, or wearing a heavy backpack tend to overestimate the steepness of a hill. These experiments indicate that people's physical-skill levels and physical characteristics affect their visual perception of objects and environments. This finding has a wide variety of practical applications. In the area of user-interface design, for example, game programmers and designers could keep games interesting by continuously altering the size of in-game objects according to a player's skill level. And developers of software for virtual-reality headsets might be able to help obese people lose weight by creating a program that reduces the apparent distance to objects, thereby eliminating visual perceptions that discourage obese people from engaging in physical activity.

Adapting environments to serve the goals and characteristics of various groups of people could become an important aspect of design in both real-world and virtual environments. This development could create a virtuous cycle of not only meeting needs when dispositions are relatively fixed but also changing dispositions through targeted environmental influences that encourage positive outcomes.