Professor Graham Davey of the University of Sussex writes that “disgust is a predominant emotion experienced in small animal phobias (particularly spider phobia), blood-injection-injury and obsessive-compulsive disorder (OCD) contamination fears”. All of these have symptoms with some functionality in common with disgust, whose primary function is to protect an organism against illness, disease and contamination.
While disgust is closely correlated with fear and anxiety, making its independent measurement problematic, the paper shows that it is sometimes possible to distinguish between them. For example, disgusting stimuli are found to cause a deceleration in heart rate rather than acceleration. When spider-related pictures were shown to individuals with a fear of spiders, their heart rate initially accelerated (suggesting fear) but then decelerated (suggesting disgust).
Disgust is also associated with a very specific facial expression which can be objectively measured in terms of muscle activation. Greater such activation “has been found in spider-fearful than in non-fearful individuals while viewing pictures of spiders or approaching spiders...as well as in blood-injection-injury [phobia] individuals viewing surgery videos”, says the paper.
Disgust is also associated with other psychopathologies including eating disorders, sexual dysfunction, hypochondriasis, height phobia and even symptoms of schizophrenia, although not all of these share the disease-avoidance functionality of disgust. The paper argues that disgust may also facilitate anxiety and distress through its involvement in more complex human emotions such as shame and guilt.