UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The causality of moral judgments : new insights into the reasoning versus intuition debate Steckler, Conor M.


During the cognitive revolution, moral judgment was seen as primarily caused by conscious language-based reasoning. At the start of the twenty-first century, a new science of morality arose, which suggested that automatic intuitions primarily cause moral judgments. More recent research has called into question the evidence for intuitive morality, supporting the possibility that conscious reasoning is critical for generating moral judgments. The aim of my dissertation is to examine the importance of intuition versus language-based reasoning for generating moral judgments. To do so, I tested a) whether interfering with the primary physiological component of disgust has causal consequences for moral judgments and b), in a split-brain patient, whether processes in the language-dominant left hemisphere are critical for generating moral judgments. More specifically, I tested whether disgust is causally related to moral judgments. To do so, I pharmacologically inhibited disgust responses to moral infractions and examined effects on moral thinking. Findings demonstrated that the antiemetic ginger (Zingiber officinale), known to inhibit nausea, reduces feelings of disgust toward non-moral purity-offending stimuli (e.g., bodily fluids), providing evidence that disgust is causally rooted in physiological nausea (Study 1; Study 5 ruled out an alternative explanation for this effect). This same physiological experience was causally related to moral thinking: ginger reduced judgment severity toward purity-based moral violations (Study 3) and eliminated the tendency for people higher in bodily sensation awareness to make harsher moral judgments (Study 4). Effects were consistently restricted to moderately severe stimuli and to purity offending stimuli: ginger had no effects on harm-based judgments (Studies 2 and 6). Together, findings provide the first evidence that disgust can be disrupted by an antiemetic and that doing so has consequences for purity-based moral judgments. Next, I examined in split-brain patient J.W. whether the right hemisphere, preferential for processing an agent’s intentions, can make typical moral judgments when informationally disconnected from the language-dominant left. I found that processes in the language dominant left hemisphere are not critical for the right hemisphere to generate adult-typical intent-based moral judgments (Study 7). Overall, findings provide renewed support for the importance of intuitive processes in generating moral judgments.

Item Citations and Data


Attribution-NonCommercial-NoDerivatives 4.0 International