IN THE AIRPORT OF THE FUTURE, a computer at the security checkpoint will read your mind and determine whether you intend to commit a terrorist act.

Science fiction? The U.S. Department of Homeland Security (DHS) doesn’t think so. In fact, it’s been working on such a computer system for years. Project Hostile Intent, a DHS research program, aimed to identify passengers who might be trying to deceive security officers (Department of Homeland Security, 2008). This effort continues today with DHS’s Future Attribute Screening Technology (FAST) project (DHS, 2011).

How does the program work? Homeland Security doesn’t tell us, exactly, because “the specific behavioral indicators being measured are sensitive information and therefore are not…discussed” (DHS, 2008, p. 2). But you can take an educated guess—at least, once you read this chapter on emotion.

When you experience an emotion, it shows on your face. Even if you try to hide the emotion, it still shows for a very brief period of time. Fleeting facial-muscle movements, known as micro-expressions, reveal inner emotional states—such as the states of stress and fear that anyone would experience when trying to sneak illegal items past a security checkpoint.

An emotions researcher, Paul Ekman, has developed a way to detect micro-expressions. In his research, high-speed video cameras capture even brief facial-muscle movements. These muscle movements uncover emotions people are trying to conceal. Dr. Ekman also has served as a consultant to Project Hostile Intent (Johnson, 2009).

In Ekman’s original research, videos of facial expressions were classified, or coded, by people—a time-consuming process. More recently, researchers have developed computer software that can code facial expressions accurately (Terzis, Moridis, & Economides, 2011). With such software in hand, Homeland Security may achieve its goal: “[a] computer [that] will analyze…behavior and identify indicators of deception” (DHS, 2008)— computerized mind-reading based on the psychology of emotion.

“WHAT ARE YOU thinking about?”

People ask this all the time. Sometimes your honest answer is “Nothing; I wasn’t thinking about anything.” You were just spacing out.

“How are you feeling?”

People ask this all the time, too. But, the honest answer never is “nothing.” You’re always feeling something: tired, peppy, bored, intrigued, angry, grateful, calm, anxious. Feelings are ever-present (Russell, 2003).

This chapter begins by exploring two types of feelings: the rapidly occurring and sometimes intense experiences we call emotions; and the relatively long-lasting but typically less intense psychological states that we call moods. After analyzing emotion and mood psychologically, we’ll move down a level of explanation to examine brain systems that contribute to these psychological experiences. Finally, we’ll focus on the emotions that arise when people are under stress, the impact of stress on physical health, and strategies you can use to make life less stressful.