Researchers excluded the purity moral foundation from their empirical measures.

Evidence

The model also includes a fifth moral foundation, purity, but in our empirical work we do not included it for two reasons. First, in our preliminary attempts to measure it using the Moral Foundations Questionnaire (MFQ; Haidt & Graham, 2007), it showed very low internal consistency. Second, it is not of much relevance to the context in which we investigated the morality shifting process. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 2127

Categorization

• QUESTION: Purity showed low internal consistency on the MFQ — worth chasing how later refinements of the MFQ fixed this.