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 of immediate needs and stressors. However, over time, the skills and resources built by broadened behaviore enhance survival.
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 participants 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 resource such as psychological resilience and flourishing.