We've all had the experience of a viscerally disgusting experience; a whiff of sour milk, your foot in something your neighbor's dog left behind, shaking hands with a sweaty palmed stranger. These triggers feel like they must be instinctively disgusting. In fact they're not and even the most basic cues to disgust have to be learned. This is because disgust is dependent on experience, socialization, personality, and context, and it is a very complex and complicated emotion. The reason humans are the only animals who experience emotional disgust is because we are the only creatures with a sufficiently sophisticated and advanced brain to be able to figure it.
Fear is an automatic and instinctive emotion that helps us when we are in harm's way fast--the tiger is leaping at you, whereas disgust is about slow and uncertain peril. We have to deduce the connection between the fact that we touched the person with the oozy red sores who then died a week later, and now we are covered in oozy red sores and what that means. This is when feeling disgusted rather than attracted to a person covered in spots is very beneficial. But it isn't always the case that disgust helps us. Many times our feelings of disgust serve no purpose, prevent us from expanding our personal and social horizons, or at worst enable us to cause harm or disregard others. But because disgust is so involved with our thoughts, it is also in our control and we don't have to be disgusted if we don't want to be. For example, if you're disgusted by earthworms you may have eliminated the possibility of ever gardening, but if you undisgusted yourself you could put something new on your bucket list. The way to undisgust yourself in this type of scenario is unfortunately to expose yourself to the object of your aversion until you reach the point where you can tolerate it without flinching. You can start out small-maybe just looking at pictures of earthworms, but gradually you'll need to be able to confront these little critters in real life without repulsion. If you have the will and work at it, you'll be happy to discover that many new and enjoyable activities become available to you.
Besides benign creepy crawlies we are also often disgusted by other people and this can cause grave social consequences. When we are disgusted by the new immigrants who have moved in next door, not only are we engulfed by the negativity and social harm of prejudice, we may also miss out on the potential for important and enlightening new experiences. Surprisingly in these cases, if we instead become empathetic towards the source of aversion we can undue disgust. This is because by being empathic we have to expose and engage with the source of our aversion, but it is also because empathy and disgust are fundamentally linked. Both emotions are processed in the same part of the brain-the anterior insula-and both are very much about the self and about protecting the self from discomfort. When I empathize with you I feel your pain and I am motivated to make you feel better because I don't want to feel bad anymore. When we are disgusted we are actually empathizing with ourselves for the awful contact we have had with dog poop, or with the thought that we too could be deformed, ill, or alien. In the case of other people, if we empathize with the person who is disgusting us, we will not only do good for another, we will do good to ourselves and become undisgusted. For example, if your first reaction to seeing an amputee is repulsion and rejection, try to help that person instead. Not only will you feel virtuous you will also feel much less disgusted by the sight of someone maimed in the future. Or, if you feel disgusted by the smells of your new neighbor's cooking, offer to help them get settled in and bring over a pot of your favorite stew instead of shunning them. Not only may you benefit from new friendship and the discovery of a novel cuisine, you will see these strangers now as more like you and have turned off your disgust towards immigrants. The bottom line is that we can control disgust, and use it or lose it.
Rachel Herz is an expert on the psychology of smell and emotion and author of the new book That's Disgusting: Unraveling the Mysteries of Repulsion.