In Hemispheric Asymmetries during Processing of Immoral Stimuli 1, Cope et al. report the results of three fMRI studies consistent with the hypothesis that, among humans, the specialized circuitry involved in processing negative morally laden stimuli is lateralized in the left hemisphere. To contextualize their research, Cope et al. describe Broca’s early recognition of both structural and functional asymmetries in the brain and cite many researchers (Vallortigara, Ross, Meadows and Kaplan, Borod, Gainotti, Demaree, Miller, and Young) who have since demonstrated functional lateralization in language, motor control, and moral and emotional processing. They then establish the central role of emotional processing in moral judgments and identify the two dominant theories of emotional lateralization: the right hemisphere hypothesis, and the valence hypothesis. Equally relevant, they also describe the leading paradigm in moral judgment research, i.e., two-process theories, which as a group posit implicit emotional processing and explicit cognitive processing as morality’s constituency. Building from the proposition that the capacity for and disposition toward moral judgments are evolved attributes of the human brain, Cope et al. set out to identify morality’s neural organization.
METHODS and RESULTS
In all three studies, subjects were screened for health and right-handedness and consent was obtained. To compare hemodynamic activity from the fMRI data collected in each study, a symmetrical template was created to allow hemilateral comparisons by averaging two mirrored hemisphere templates. In a further wave of refinement, hemodynamic activity amplitude in each hemisphere was subtracted from that of the other. After a significance screening, an algorithm was used to color code hemodynamic asymmetries into three categories before a final effects mask was used to screen out false positives. Once the data sets from each study had been fully synthesized, a conjunction analysis was used to identify brain activity and variables common to all three.
STUDY 1: IMPLICIT EVALUATIONS OF MORAL AND NON-MORAL ACTS IN A MEMORY-RECOGNITION TASK
In total, 144 statements were divided first into 2 “runs” of 12 memorize-recognize blocks, each of which contained 6 statements. In each block, subjects were shown a series of 4 statements (memorize phase). Subjects were then asked to identify each of 4 subsequent statements as either repeated from the memorize phase, or novel. Statements were of one of 4 types, pathogen-related, incestuous, non-sexual immoral, or neutral. Subject statement evaluation was monitored via fMRI, which constituted the analyzed data.
Cope et al.’s laterality analysis identified left BA 8, BA 8/10, BA 37, BA 40, BA 31/7/24, BA 6, and the right cerebellum as significantly more active during processing of negative morally laden stimuli than during processing of neutral stimuli, and left BA 10/11 and BA 20, and right BA 21, BA 22, BA 40, and BA 31 as significantly more active during processing of negative morally laden stimuli than during processing of disgusting, non-moral stimuli.
STUDY 2: EXPLICIT EVALUATION OF MORAL ACTS: JUDGING ACTS TO BE “WRONG” OR “NOT WRONG”
One-hundred and fifty statements were evaluated and judged by participants to be either wrong or not wrong, each belonging to 1 of 3 categories: immoral, moral, and controversial. Again, fMRI data were obtained and analyzed.
Cope et al.’s laterality analysis identified greater significant activity in left BA 9, BA 10, BA 47, and BA 7 associated with the evaluation that controversial statements were wrong than with the judgment of non-controversial statements as wrong.
STUDY 3: EXPLICIT EVALUATION OF PICTURES DEPICTING MORAL ACTS: JUDGING HOW WRONG IS EACH ACT
A total of 75 images from the International Affective Picture System were organized into 3 categories, immoral, non-moral w/ negative valence, and neutral. Under MRI conditions, subjects evaluated whether the actions contained in each image constituted a moral violation, and if so, to what degree (1 to 5 scale).
Upon laterality analysis, Cope et al. found that significantly greater activity in left BA 37, BA 7/19, BA 40, BA 10/32, and BA 28/36/19 was associated with viewing immoral image content than with viewing non-moral image content.
Areas of significant activation within the left hemisphere common to all three studies included BA 10, BA 8, BA 31, BA 39, BA 21, and BA 20, and within the right hemisphere, BA 32 and BA 39.
COPE ET AL.’s CONCLUSIONS
Cope et al. claim that in the three studies analyzed, the left hemisphere was more actively engaged in the processing of moral violations than the right hemisphere, and further, that this pattern cannot be explained by a left hemisphere stimuli bias, nor by emotional arousal as confounding factors. The authors conclude that moral judgment may be left-lateralized, or perhaps it is the judgment (made elsewhere) of moral violation that activates key modules in the left hemisphere. Identification or analysis of immoral acts appears to be a functional specialization of left-lateralized circuitry, evolved as such because of the efficiency inherent to lateralization strategies.
EVALUATION of RESEARCH
I generally agree with Cope and his coauthor’s interpretation and conclusions, though I don’t think they adequately distinguished among the particular components likely to contribute to moral judgments, that is, the individual studies were not designed to give the resolution necessary for dissecting the neural substrates of moral judgments. I also think they did a poor job of accounting for their initial hypothesis, which was introduced in the background section in the context of its contradiction to existing evidence and theory. No reasoning was given to support why they would have expected to find moral violation processing to be left lateralized.
Interestingly, their results are consistent with my own study’s findings 1) that a specific subsystem involved in processing the “positive-subtraction” component (that is, the negative cost of an immoral component) of a valently positive, cost/benefit-activating moral stimulus is left lateralized, and 2) that a separate subsystem contributing to “self-positive” processing of self-affecting, valently positive moral stimuli is right lateralized. This overlap is further encouraging in that the methods and technologies used between Cope et al.’s studies and my own were radically different, which suggests that the agreements between them converge on real phenomena, however poorly characterized they may remain for now.
RELEVANT VIDEO: MOLLY CROCKETT
1. Cope LM, Borg JS, Harenski CL, et al. Hemispheric Asymmetries during Processing of Immoral Stimuli. Front Evol Neurosci. 2010;2..
- CVS Modulates Moral Judgments (leeware.wordpress.com)