- Core disgust
- Disgust at things that could act as vehicles for disease or contamination — bodily products (faeces, vomit, blood, sweat), decay and rot, certain animals (insects, rats, slugs), certain foods (especially meat and fish past their best). Rozin identifies this as the evolutionarily primary form of disgust, conserved across cultures with variation in the specific eliciting objects.
- Moral disgust
- Disgust triggered by violations of moral purity or social norms, particularly those involving sex, the body, or sacred values. Haidt argues that the Moral Foundations of Purity/Sanctity rely on disgust as their emotional substrate. Moral disgust recruits the same anterior insula and basal ganglia as physical disgust, suggesting the brain reuses the same system for both.
- Contamination sensitivity
- Individual differences in the tendency to perceive objects and situations as contaminating. Measured by Rozin's Disgust Scale (DS-R). High contamination sensitivity predicts OCD contamination symptoms, washing behaviours, and avoidance of objects perceived as impure, even when intellectually known to be clean.
- The law of contagion
- Once in contact with a disgusting object, items are perceived as permanently contaminated, regardless of washing or time elapsed. Rozin demonstrated that people refuse to drink juice after a sterilised cockroach has been dipped in it. This "once in contact, always contaminated" rule is a defining feature of disgust logic that distinguishes it from other threat responses.
- The law of similarity
- Objects that resemble disgusting things become disgusting themselves — even if they are neutral in reality. Fudge shaped like dog faeces is unappealing; a food formed to look like a cockroach is rejected. Similarity alone — without actual contact — is enough to trigger disgust.
- Anterior insula
- The neural hub most consistently associated with disgust, particularly primary (taste-based) disgust and the physical experience of nausea. The insula also processes interoceptive signals — internal body states — making it a natural seat for an emotion fundamentally about what the body takes in. Activation extends to the basal ganglia in both physical and moral disgust.