Ben Franklin might have been wrong about human magnetism. When Franklin was in Paris in the late 1700s, he led the effort to discredit the magnetism cures of Mesmer (the guy at the root of the word mesmerize). Mesmer claimed to be able to cure people of physical and psychological ailments by applying magnetism - he would wave a magnet over various body parts. Franklin argued, quite compellingly, that social conformity was leading to the cures, not animal magnetism. Recently, however, researchers have found that magnets can change human thoughts. For example, Liane Young and her colleagues have reported that magnetic stimulation can alter adult moral reasoning - making it resemble reasoning by young children.

Moral judgments often require weighing multiple factors and making complex evaluations. For example, imagine you hear about a woman who died because of a poisonous powder that was added to her coffee. Her good friend added the poison. Horrible, you think, what could cause someone to murder a friend? Then you learn that the friend thought she had put sugar in the coffee and that she called 911 as soon as she realized her friend was in trouble. How awful, you think, a tragic accident that will haunt the friend for years. What if you learn that the friend had recently discovered that the woman was having an affair with her husband and that the friend had ready access to poisons because she worked in a chemical factory. Hmm, you wonder, is she lying, did she kill her friend?

When adults reason about morality and ethics, they consider two important types of evidence: outcome and intentionality. In the example of the poisoned coffee, the outcome can be manipulated - the woman can receive poison or she can receive sugar (and thus die or happily enjoy her cup of coffee). The intentionality can be manipulated as well - the friend can believe she is adding sugar or poison to the coffee. Generally, adults value both types of information in making moral judgments. We blame people more for a negative outcome when they intend to cause harm. Most legal systems also note the distinction between unintentionally killing someone (manslaughter) and intentionally killing the person (murder).

Young children are less adept at balancing outcome and intentionality information. Children tend to rely more heavily on outcome information. If someone gets hurt, then the person who caused the harm is to blame - regardless of their intentions. I suspect this is related to general issues of theory of mind. Children only gradually come to understand that other people have knowledge, beliefs, and intentions that differ from their own.

temporoparietal junction

Liane Young and her colleagues (Young, Camprodon, Hauser, Pascual-Leone, and Saxe) recently used magnetic stimulation to make adults reason about morality more like children do (the paper is forthcoming in PNAS but available online through early release). Young and her colleagues applied transcranial magnetic stimulation to the right temporoparietal junction (a fancy way of saying they waved powerful magnets over a particular part of the brain; see the circled area in the picture). They magnetized a part of the brain already suspected to be involved in moral judgments. Since much of neural functioning depends on electrical transmission along neurons, the magnet can temporally disrupt neural function in that part of the brain. Compared to control conditions, the individuals who experienced magnetic stimulation made less use of intentionality information. Their judgments were based more on the outcome (whether the woman died or enjoyed her coffee) and less on the intentionality of the coffee server (whether the friend believed she had put sugar or poison in the coffee). The right temporoparietal junction appears particularly important for using intentionality information in making moral judgments.

Should this type of work lead to a reappraisal of the old argument between Franklin and Mesmer? Probably not. Mesmer's effects were not caused by the magnets - Franklin was right. Nonetheless magnetic stimulation has been used as a treatment option in depression in recent years. So perhaps Mesmer had a rather current idea over 200 years ago. Young and her colleagues have demonstrated that magnets may become powerful causal tools for neuroscience investigations of Psychology. We also might want to keep powerful magnets away from deliberating juries.

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