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Engaged neurons

Daniel BuenoIn 2005, a ban on the sale of firearms in Brazil was rejected by almost two thirds of voters in a referendum. For weeks, publicity campaigns presented arguments for both sides: the dangers of gun availability and the ineffectiveness of gun control in Brazil. But a recent study suggests that these arguments failed to influence voters’ decisions. Coordinated by Armando Freitas da Rocha and Eduardo Massad at the USP School of Medicine, the researchers monitored the brain activity of 1,136 individuals as they answered a questionnaire about the referendum (Journal of Behavioral and Brain Science, December 2014). The results showed that arguments in favor of gun control were considered truthful by 50% of the participants, but only 20% said that the arguments presented by the media would have any weight in their voting decisions. An interesting detail is that the brains of the participants activated different neural circuits when they were analyzing arguments against or in favor of gun control. Favorable arguments activated neurons in regions associated with retrospective and episodic memory and with assessments of other people’s intent. Contrary arguments were processed by neurons in regions associated with assessments involving self-interest. A larger number of neurons was generally activated as participants considered the arguments for gun control, suggesting that these arguments require a more complex analysis than do those against the ban.