Broaden-and-build

The broaden-and-build theory of positive emotions suggests that positive emotions (viz. enjoyment/happiness/joy, and perhaps interest/anticipation) broaden one's awareness and encourage novel, varied, and exploratory thoughts and actions. Over time, this broadened behavioral repertoire builds skills and resources. For example, curiosity about a landscape becomes valuable navigational knowledge; pleasant interactions with a stranger become a supportive friendship; aimless physical play becomes exercise and physical excellence.

This is in contrast to negative emotions, which prompt narrow, immediate survival-oriented behaviors. For example, the negative emotion of anxiety leads to the specific fight-or-flight response for immediate survival. On the other hand, positive emotions do not have any immediate survival value, because they take one's mind off immediate needs and stressors. However, over time, the skills and resources built by broadened behavior enhance survival.

When a life-threatening event occurs, people typically have a narrow range of possible responses or urges. Having a limited number of urges, called specific action tendencies, quickens a person's response time in these situations. While negative emotions experienced during life-threatening situations narrow an individual's thought-action repertoire, positive emotions present new possibilities, providing the individual with a wider range of thoughts and actions to choose to draw upon.

The broaden-and-build theory is an exploration of the evolved function of positive emotions. It was developed by Barbara Fredrickson starting around 1998 and is commonly associated with positive psychology.

The broaden-and-build theory has substantial support. Barbara Fredrickson has conducted randomized controlled lab studies in which participants are randomly assigned to watch films that induce positive emotions such as amusement and contentment, negative emotions such as fear and sadness, or no emotions. Compared to people in the other conditions, participants who experience positive emotions show heightened levels of creativity, inventiveness, and "big picture" perceptual focus. Longitudinal intervention studies show that positive emotions play a role in the development of long-term resources such as psychological resilience and flourishing. Not only are positive emotions a sign of flourishing, or thriving and expanding in life rather than simply surviving life, they can also help create flourishing in the present and in the future. Because positive emotions positively broaden and build one's thought-action repertoires they lead to increased resources and more satisfied lives.

...
Wikipedia