Magnetic manipulation of the sense of morality : Neurophilosophy

Liane Lee Young of MIT’s Department of Brain and Cognitive Science and her colleagues asked participants to make moral judgements about different variations of a number of scenarios. One of these involves Grace and her friend having a cup of coffee during a tour of a chemical plant. In one version of it, she puts what she rightly believes to be sugar into her friend’s drink; in another, she puts what she believes to be poison, but what is actually sugar, into the drink; in the third variation, Grace puts poison into the cup, thinking it is sugar, and her friend dies; and in the final variation, she knowingly puts poison into the drink.

These scenarios differ in the beliefs underlying Grace’s actions and in their outcome. Most of us would agree that she acts “wrongly” by poisoning her friend in the fourth variation of the scenario. She was also wrong in the second, because although the outcome was neutral, she attempted to cause harm to her friend. On the other hand, most would agree that she was not wrong in the unfortunate scenario in which she unwittingly poisoned her friend. Although her act was guilty, her mind was not – it was not her intention to kill.

The researchers used an experimental technique called transcranial magnetic stimulation (TMS) to disrupt activity in the right temporoparietal junction (RTPJ), a region of the brain located just behind the ear which has previously been implicated in understanding the behaviour of others. In the “offline” condition, the participants received low frequency (1 Hz) magnetic pulses to the RTPJ or to a nearby control region for 25 minutes before reading the moral scenarios and making judgements about them. In the “online” condition, higher frequency bursts lasting half a second were applied while the participants read and judged the scenarios.

In both experiments, TMS applied to the RTPJ but not to the control brain region was found to impair the participants’ ability to make sound moral judgements in some cases but not in others. Judgements of scenarios involving intentional harm or no harm were unaffected, but the scenarios in which one character attempted unsuccessfully to harm another were judged to be more morally permissible. In other words, disrupting RTPJ activity significantly reduced the influence of belief on the participants’ judgements, so that they relied purely on the outcome of the scenarios, rather than on the intentions or motives of the character.

The authors conclude that the RTPJ is specifically required for attributing beliefs to others, or is part of a network containing a number of brain regions which are jointly necessary for belief attribution. The RTPJ appears to be strongly connected to other brain regions implicated in various aspects of social cognition, including attributing mental mental states to others. More evidence comes from another study by the same researchers published in the journal Neuron last week, which shows that moral judgements are also impaired in patients with damage to the ventromedial prefrontal cortex. Alternatively, perturbing RTPJ activity may have disturbed other cognitive functions, such as attention – it lies near a network known to be involved in attentional switching, but is anatomically distinct from it.  

Whether or not these findings extend to real world judgements remains to be seen. They may, however, have implications for autistics, who are thought to be incapable of inferring the mental states of others. Young and her colleagues hypothesize that autistic children and adults will exhibit deficits in the types of moral judgements used in this study, and are now testing this prediction. Interestingly, children up to the age of 6 years rely mainly on the outcomes of actions to make moral judgements, and tend to judge those who hurt somebody accidentally as being naughtier than someone who attempts to harm another but fails. This may be related to the late maturation of the RTPJ, and is another topic worthy of further investigation.


Young, L., et al. (2010). Disruption of the right temporoparietal junction with transcranial magnetic stimulation reduces the role of beliefs in moral judgments. Proc. Nat. Acad. Sci. DOI: 10.1073/pnas.0914826107.

Saxe, R. & Kanwisher, N. (2003). People thinking about thinking people: The role of the temporo-parietal junction in “theory of mind”. NeuroImage 19: 1835-1842. [PDF]

Baron-Cohen, S., et al (1985). Does the autistic child have a “theory of mind”? Cognition 21: 37-46. [PDF]

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