Brain Stimulation Decreases Intent to Commit Assault

Summary: A new study reveals the desire to carry our physical or sexual assault can be curbed with the help of tDCS. The brain stimulation technique also increases the perception in potential offenders that such violence is morally wrong.

Source: University of Pennsylvania.

Stimulating the prefrontal cortex, the part of the brain responsible for controlling complex ideas and behaviors, can reduce a person’s intention to commit a violent act by more than 50 percent, according to research from the University of Pennsylvania and Nanyang Technological University published in the Journal of Neuroscience. What’s more, using such a minimally invasive technique, called transcranial direct-current stimulation, increased the perception that acts of physical and sexual assault were morally wrong.

“The ability to manipulate such complex and fundamental aspects of cognition and behavior from outside the body has tremendous social, ethical, and possibly someday legal implications,” says Roy Hamilton, a neurologist at Penn’s Perelman School of Medicine and the senior paper author.

It’s viewing violent crime from a public-health perspective, adds psychologist Adrian Raine, a Penn Integrates Knowledge Professor and co-author on the paper. “Historically we haven’t taken this kind of approach to interventions around violence,” he says. “But this has promise. We only did one 20-minute session, and we saw an effect. What if we had more sessions? What if we did it three times a week for a month?”

To draw these conclusions, the research team conducted a double-blind randomized control trial on 81 healthy adults ages 18 or older. At the start of the study, participants were randomly assigned to one of two groups. The first received stimulation on the prefrontal cortex for 20 minutes; the second, the placebo group, received a low current for 30 seconds, then nothing more. Participants did not know their group assignment nor did the individual conducting each experiment.

The researchers zeroed in on the prefrontal cortex—and specifically, the dorsolateral prefrontal cortex in the top, front area of the brain—because it’s well-documented that antisocial individuals have deficits in this region, says Olivia Choy, an assistant professor in psychology at NTU in Singapore and the lead author on the paper.

“If an offender’s brain is scanned, we don’t really know if it’s the brain deficit that leads to the behavior or if it’s the other way around,” says Choy, who earned her doctoral, master’s, and bachelor’s degrees from Penn. “One of the main objectives of this study was to see whether there was a causal role of this brain region on antisocial behavior.”

After the stimulation, the researchers presented participants with two hypothetical scenarios, one each about physical and sexual assault, and asked them to rate on a scale of 0 to 10 (with 0 being no chance and 10 being 100 percent) the likelihood that they would act as the protagonist in the vignettes. For those in the experimental group, stimulation decreased their intent to carry out physical and sexual assault by 47 and 70 percent, respectively. Participants also rated on the same 0-to-10 scale how morally wrong they felt the scenarios were.

“We chose our approach and behavioral tasks specifically based on our hypotheses about which brain areas might be relevant to generating aggressive intentions,” Hamilton says. “We were pleased to see at least some of our major predictions borne out.”

In theory, the results mean that simple biological interventions—either separately or in conjunction with psychological interventions like cognitive behavioral therapy—have the potential to reduce violent behavior.

“Much of the focus in understanding causes of crime has been on social causation,” Raine says. “That’s important, but research from brain imaging and genetics has also shown that half of the variance in violence can be chalked up to biological factors. We’re trying to find benign biological interventions that society will accept, and transcranial direct-current stimulation is minimal risk. This isn’t a frontal lobotomy. In fact, we’re saying the opposite, that the front part of the brain needs to be better connected to the rest of the brain.”

the researcher carrying out tDCS
Roy Hamilton of Penn Medicine (left) was part of a research team that studied whether a minimally invasive brain stimulation, similar to what he’s demonstrating in this photo, can reduce someone’s intent to commit a violent crime. image is credited to the University of Pennsylvania.

Despite the encouraging results, Choy makes it clear there’s more work necessary before it’s certain this type of treatment will reduce violence. The study needs to be replicated, then built upon, she says.

New research lead by Hamilton with Shichun Ling, a doctoral candidate in Penn’s Department of Criminology in the School of Arts and Sciences, focuses on high-density transcranial direct-current stimulation, a higher-resolution approach that activates smaller portions of the prefrontal cortex like the frontal pole. The researchers also say they want to know more about what happens when such stimulation is administered over longer periods, as well the overall long-term effects of this kind of treatment.

“This is not the magic bullet that’s going to wipe away aggression and crime,” Raine says. “But could transcranial direct-current stimulation be offered as an intervention technique for first-time offenders to reduce their likelihood of recommitting a violent act?”

The researchers are not yet ruling out anything.

“Perhaps,” Hamilton concludes, “the secret to holding less violence in your heart is to have a properly stimulated mind.”

About this neuroscience research article

Funding: This work was funded in part by the BRAIN Initiative through NIBIB (EB022907), the National Institute of Mental Health (MH105625), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (HD074652), and the National Institute of Neurological Disorders and Stroke (NS086085), all part of the NIH. Within the BRAIN Initiative’s diverse research categories, its area is Theories, Models and Methods for Analysis of Complex Data from the Brain.

Source: University of Pennsylvania
Publisher: Organized by
Image Source: image is credited to the University of Pennsylvania.
Original Research: Abstract for “Stimulation of the Prefrontal Cortex Reduces Intentions to Commit Aggression: A Randomized, Double-Blind, Placebo-Controlled, Stratified, Parallel-Group Trial” by Olivia Choy, Adrian Raine and Roy H. Hamilton in Journal of Neuroscience. Published July 2 2018.

Cite This Article

[cbtabs][cbtab title=”MLA”]University of Pennsylvania”Brain Stimulation Decreases Intent to Commit Assault.” NeuroscienceNews. NeuroscienceNews, 3 July 2018.
<>.[/cbtab][cbtab title=”APA”]University of Pennsylvania(2018, July 3). Brain Stimulation Decreases Intent to Commit Assault. NeuroscienceNews. Retrieved July 3, 2018 from[/cbtab][cbtab title=”Chicago”]University of Pennsylvania”Brain Stimulation Decreases Intent to Commit Assault.” (accessed July 3, 2018).[/cbtab][/cbtabs]


Stimulation of the Prefrontal Cortex Reduces Intentions to Commit Aggression: A Randomized, Double-Blind, Placebo-Controlled, Stratified, Parallel-Group Trial

Although prefrontal brain impairments are one of the best-replicated brain imaging findings in relation to aggression, little is known about the causal role of this brain region. This study tests whether stimulating the dorsolateral prefrontal cortex (DLPFC) using transcranial direct current stimulation (tDCS) reduces the likelihood of engaging in aggressive acts, and the mechanism underlying this relationship. In a double-blind, stratified, placebo-controlled, randomized trial, 81 human adults (36 males, 45 females) were randomly assigned to an active (N = 39) or placebo (N = 42) condition, and followed up one day after the experiment session. Intentions to commit aggressive acts and behavioral aggression were assessed using hypothetical vignettes and a behavioral task, respectively. The secondary outcome was the perception of the moral wrongfulness of the aggressive acts. Participants who received anodal stimulation reported being less likely to commit physical and sexual assault (p < .01), and judged aggressive acts as more morally wrongful (p < .05) compared to the sham controls. 31% of the total effect of tDCS on intentions to commit aggression was accounted for by perceptions of greater moral wrongfulness regarding the aggressive acts. Results provide experimental evidence that increasing activity in the prefrontal cortex can reduce intentions to commit aggression and enhance perceptions of moral judgment. Findings shed light on the biological underpinnings of aggression and theoretically have the potential to inform future interventions for aggression and violence.

Trial Registration identifier: NCT02427672


Aggressive behaviors pose significant public health risks. Understanding the etiology of aggression is paramount to violence reduction. Investigations of the neural basis of aggression have largely supported correlational, rather than causal interpretations, and the mediating processes underlying the prefrontal-aggression relationship remain to be well-elucidated. Through a double-blind, stratified, placebo-controlled, randomized trial, this study tested whether upregulation of the prefrontal cortex reduces the likelihood of engaging in aggression. Results provide experimental evidence that increasing prefrontal cortical activity can reduce intent to commit aggressive acts. They also shed light on moral judgment as one mechanism that may link prefrontal deficits to aggression and in theory, have the potential to inform future approaches towards reducing aggression.

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