Basic emotions regulate us in response to environmental challenges and opportunities. While there is no definitive list of basic emotions, one popular one (from emotion expert Paul Ekman) contains six: fear, anger, sadness, disgust, surprise, and joy. These six have been found in every culture worldwide, and have also been shown to be identifiable by people crossculturally. This suggests that they are evolved responses rather than cultural expressions. Looking at each emotion in turn, it’s easy to gain an understanding of their evolutionary function:
Fear—The function of fear is to get us out of dangerous situations, or to keep us from getting into them. It causes the heart to race, breathing to speed up, and so on, preparing our bodies to take appropriate action, such as running as fast as we can.
Anger—The function of anger is to motivate us to defend or protect ourselves, our loved ones, or anything that we consider valuable. Anger gears up the body into a combat-ready mode, inducing such expressions as narrowed eyes and lips (making them harder to damage in a fight), balling the fists, hunching the shoulders, and so on.
Sadness—The function of sadness is to indicate that we have done or witnessed something that is damaging or degrading to wellbeing, and to encourage us not to do that in the future. Sadness causes the eyebrows to move upward at the inside corners, the lower lip to push outward, and the body posture to slump. Tears running from our eyes indicates an even stronger experience of sadness.
Disgust—The function of disgust is to keep us from contacting or ingesting dangerous, toxic, or infectious substances. Disgust causes the upper lip to curl and the nose to wrinkle, constricting the facial orifices away from the thing causing disgust. A feeling of disgust may even cause retching or full-on vomiting.
Joy—The function of joy is to indicate that we have done or witnessed something that is enhancing to wellbeing, and to encourage us to do that in the future. When we are joyful, we smile, the corners of our eyes crinkle, and our posture becomes upright and open.
Surprise—The purpose of surprise is to indicate that something unexpected has occurred, to prepare us (and those around us) to deal with it. Surprise causes our eyes to fly wide open, the eyebrows raise, and the jaw drops open.
Why are there so many more negative emotions than positive ones? Because while life-enhancing actions are helpful, life-negating actions are often lethal. Since the downside of life-negating actions is much larger than the upside of life-enhancing ones, it is important that the negative emotions be very specific. The best example is disgust, which is mainly to force you to spit out toxic foods that might make you sick or even kill you, or to keep you from eating them in the first place. Surprise can be either negative or positive, depending on what has caused it. Interestingly, anger could be considered a positive emotion, in that many people report that anger makes them feel good, energized, and motivated.
While emotions evolved to motivate and direct our behavior, we evolved under conditions that were very different from the ones we currently live in. This means that oftentimes our emotions are out of sync with our current environment. For example, in our ancestral environments we probably encountered very few strangers and very few loud sounds. Yet in a modern urban environment we are surrounded by strangers and loud noises, leading some psychologists to suggest that this mismatch may be a cause of anxiety and depression.