The study by Schnall and colleagues illustrates the causal limitations of non-manipulated variables. While researchers could conclude that the manipulated variable of disgust affected the harshness of moral judgments, they could not make the same causal claim about private body consciousness. Because private body consciousness was only measured and not manipulated, any association with moral judgments might be caused by an unmeasured third variable, such as neuroticism, that independently increases both bodily awareness and moral strictness.