The Effect of Cognitive-Processing Manipulations on Moral Judgment: A Systematic Review and Meta-Analysis

A major question in moral psychology revolves around the role of deliberation or reflection in moral judgment. One common approach to investigating this question is to study the effect of cognitive-processing manipulations on moral judgment, which are experimental manipulations designed to either encourage participants to engage in reflection, or to inhibit their ability to reflect. Both psychologists and philosophers often appeal to studies of this sort to argue that reflection should, does or fails to make a significant contribution to moral judgment in many circumstances (often compared to a more intuitive type of processing).<br> This article presents the first systematic review of the psychological literature on the effect of cognitive-processing manipulations on moral judgments. I identified a total of 58 articles for inclusion, reporting results from 99 studies (total <i>N</i> = 19,341; <i>M</i>(<i>N</i>) = 199.4). Since a large majority of these studies involved moral judgments about acts or decisions in sacrificial moral dilemmas, the review is split in two parts. In the first part, I provide a narrative synthesis of studies that involved moral judgments about stimuli other than sacrificial dilemmas, organized by the area of morality that participants made moral judgments about. I then present a meta-analysis of the remaining 72 studies (total <i>N</i> = 16,104;&nbsp;<i>M</i>(<i>N</i>) = 230.1), which all investigated the effect of cognitive-processing manipulations on moral judgments about acts or decisions in sacrificial moral dilemmas. While there was a small, significant pooled effect, when taking small- publication bias into account, this effect became indistinguishable from zero. I argue that these results do little to support the influential Dual Process Model of moral judgment.<br> To end, I discuss how the results of my review bear on several topics within moral philosophy, including moral rationalism and moral progress, and sketch a number of potential avenues for future research.