Neville Longbottom x Severus snape smut

Second part

In a series of significant studies by Paul Ekman in the 1970s, it was discovered that facial expressions of emotion are not culturally determined, but universal across human cultures and thus likely to be biological in origin.[25] The facial expression of disgust was found to be one of these facial expressions. This characteristic facial expression includes slightly narrowed browsthe tongue is moved forward or protruded, waving the hand back and forth although different elicitors may produce different forms of this expression.[26] It was found that the facial expression of disgust is readily recognizable across cultures.[27] This facial expression is also produced in blind individuals and is correctly interpreted by deaf individuals.[7] This evidence indicates an innate biological basis for the expression and recognition of disgust. The recognition of disgust is also important among species as it has been found that when an individual sees a conspecific looking disgusted after tasting a particular food, he or she automatically infers that the food is bad and should not be eaten.[6] This evidence suggests that disgust is experienced and recognized almost universally and strongly implicates its evolutionary significance.

Facial feedback has also been implicated in the expression of disgust. That is, the making of the facial expression of disgust leads to an increased feeling of disgust. This can occur if the person just wrinkles one's nose without awareness that they are making a disgust expression.[28]

The mirror-neuron matching system found in monkeys and humans is a proposed explanation for such recognition, and shows that our internal representation of actions is triggered during the observation of another's actions.[29] It has been demonstrated that a similar mechanism may apply to emotions. Seeing someone else's facial emotional expressions triggers the neural activity that would relate to our own experience of the same emotion.[30] This points to the universality, as well as survival value of the emotion of disgust.

Children's reactions to a face showing disgust
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At a very young age, children are able to identify different, basic facial emotions. If a parent makes a negative face and a positive emotional face toward two different toys, a child as young as five months would avoid the toy associated with a negative face. Young children tend to associate a face showing disgust with anger instead of being able to identify the difference. Adults can make the distinction. The age of understanding seems to be around ten years old.[31]