Jean Decety from the University of Chicago and his coworkers have recently published on Cerebral Cortex an article that studies the development of morality using a variety of techniques, including fMRI, eye-tracking, and explicit questionnaires.
One novelty of this experiment is the age distribution of the large experimental sample: Contrary to most studies, who mostly make use of freshmen, Decety and colleagues studied kids aged 4 as well as 37-year-old adults. No explicit task was required from the subjects. They were simply shown visual stimuli in which persons or objects were damaged, either intentionally or accidentally. After the scanning session the subjects were shown the stimuli again and had to rate their empathic concern for the victim, personal distress, understanding of the perpetrator’s mind (‘how mean was the person who did this?’), moral evaluation, and desire to punish the perpetrator.
To my knowledge this is the first paper addressing in a systematic way the neural correlates of moral development across age classes. Factors such as intention and target of the damage conserve their effect across all age classes. Even though moral evaluation and correlated brain activity is remarkably similar in kids and adults, there are differences too. In particular the amygdala and the anterior insula – two notably emotive parts of the brain – are more active in young subjects, giving way to higher prefrontal cortex activations in older subjects. Older people tend to be less aroused and empathic than children when objects are damaged or accidental harm is caused: The strength of the ‘intention’ and ‘target’ factors thus increases with age. Another interesting finding is that the amygdala and the ventro-medial prefrontal cortex (VMPFC) integrate more from the point of view of functional connectivity as the years go by. This leads to a better regulation of the amygdala by the VMPFC cortex. Finally, Decety et al find a correlation between the OrbitoFrontal Cortex and the right hippocampus and the extent to which subjects want to punish the perpetrator.
The overall picture is that moral development is initially driven by structures that mediate emotional saliency, such as the amygdala and the insula. Then prefrontal structures gradually mature and integrate with amygdala and insula, leading to a heightened sensitivity to both intention and the severity of consequences. Prefrontal cortexes allow to better regulate the activity of emotional regions and to integrate their outputs together. In fact adults are less likely than children to want to punish people who broke objects or who caused accidental harms. The data confirm that emotional structures in the human brain are paramount for moral development, but also underline a better capability in adults to control the drive to punish if the action harms objects or is accidental, thanks to mature prefrontal areas.
Decety J, Michalska K J, and Kinzler K D. 2011. The contribution of emotion and cognition to moral sensitivity: a neurodevelopmental study. Cerebral Cortex: e-published ahed of print, May 26 2011.
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