1. Data Collection

1. Conduct a power analysis and recruit a sufficient number of participants.
2. Create 30 moral dilemmas divided equally into categories of (1) personal moral dilemmas, (2) impersonal moral dilemmas, and (3) non-moral dilemmas. See the supplementary materials from Greene et al. for specific examples.¹
   1. A personal moral dilemma involves the participant imagining to perform an action that directly harms one person in the service of some goal. Examples include the footbridge dilemma, harvesting the organs of a person to save several other people, and throwing someone off a lifeboat to save others on the boat.
   2. An impersonal moral dilemma involves the participant imagining to perform an action that indirectly harms one person in the service of some goal. Examples include the trolley dilemma, cheating on taxes, and stealing a boat in order to save people from a storm.
   3. A non-moral dilemma involves the participant imagining to perform an action that is not typically viewed in moral terms at all. Examples include deciding to buy a name-brand versus an off-brand medicine and whether to travel by plane or train given certain time constraints.
3. Present every participant with each of the 30 dilemmas while undergoing brain scanning using fMRI.
   1. Verify that stimuli (dilemmas) are shown on a visual display projected into the scanner.
   2. Present each dilemma as text through a series of three screens, the first two describing a scenario and the last posing a question about the appropriateness of an action one might perform in that scenario (e.g., turning the trolley).
   3. Give participants 46 s maximum to get through all three screens.
   4. Note that the intertrial interval (ITI) lasts for a minimum of 14 s (seven images) in each trial.
   5. Define baseline activity as the mean signal across the last four images of the ITI.
   6. Measure task-related activity using a “floating window” of eight images surrounding (four before, one during, and three after) the point of response.
      1. This window includes three post-response images in order to allow for the 4- to 6-s delay in hemodynamic response to neural activation.
   7. Acquire functional images in 22 axial slices parallel to the AC-PC line (echoplanar pulse sequence; TR, 2000 ms; TE, 25 ms; flip angle, 90°; FOV, 192 mm; 3.0-mm isotropic voxels; 1-mm interslice spacing) using a 3.0-T Siemens Allegra head-dedicated scanner.
4. Dependent measure: Measure participants’ moral judgments by their rating of whether or not the action described in the dilemma was appropriate or inappropriate (binary choice).

2. Data Analysis

1. Before statistical analysis, co-register images for all participants using a 12-parameter automatic algorithm and smooth with an 8-mm full width at half maximum 3D Gaussian filter.
2. Analyze fMRI scans for each participant during each task.
   1. For the images contained in each response window, use a voxel-wise mixed-effects ANOVA with participant as a random effect, and dilemma-type, block, and response-relative image as fixed effects.
   2. Threshold statistical maps of voxel-wise F-ratios for statistical significance (p = 0.0005) and cluster size (8 contiguous voxels).
   3. Threshold the planned comparisons for significant differences between conditions for statistical significance (p = 0.05 and cluster size (8 voxels).
3. Measure the percentage change, relative to the baseline, in brain activity for each of the crucial brain areas at play.