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Bullies may enjoy others’ pain

Nov. 7, 2008
Courtesy University of Chicago
and World Science staff

Un­u­su­ally ag­gres­sive youth may en­joy in­flict­ing pain, re­search­ers at the Uni­ver­s­ity of Chi­ca­go have found in a study us­ing brain scans. Vid­eos of peo­ple get­ting hurt were found to trig­ger flur­ries of ac­ti­vity in a brain ar­ea as­so­ci­at­ed with re­ward in ag­gres­sive youth, the sci­en­tists said; oth­er kids did­n’t re­act that way.

For ag­gres­sive ad­o­les­cents, see­ing some­one in pain trig­gered strong ac­tiva­t­ion in a brain ar­ea called the ven­tral stria­tum, which re­sponds to pleas­ur­a­ble events, re­search­ers said. (Im­age cour­tesy Open Uni­ver­sity, U.K.)


The re­search shows some ag­gres­sive youths’ nat­u­ral em­pa­thet­ic im­pulse may be dis­rupted, said the uni­ver­s­ity’s Jean De­cety, who led the re­search. “This work will help us bet­ter un­der­stand ways to work with ju­ve­niles in­clined to ag­gres­sion and vi­o­lence,” he added.

The sci­en­tists com­pared ad­o­les­cent boys with no un­usu­al signs of ag­gres­sion to eight 16- to 18-year-old boys who had shown dis­rup­tive be­hav­ior, such as start­ing a fight, us­ing a weap­on or steal­ing af­ter con­fronting a vic­tim. 

Par­ti­ci­pants un­der­went brain scans while watch­ing videos of peo­ple hav­ing their foot stepped on, hav­ing a heavy bowl fall on their hands, or the like. The scan­ning sys­tem was of a widely used type known as func­tion­al Mag­net­ic Res­o­nance Im­ag­ing, which meas­ures brain ac­ti­vity based on where blood is flow­ing.

Ag­gres­sive ad­o­les­cents showed a “spe­cific and very strong ac­tiva­t­ion” in a brain ar­ea called the ven­tral stria­tum, known from pre­vi­ous stud­ies to re­spond to pleas­ur­a­ble events, De­cety said. Un­like the con­trol group, he added, the more ag­gres­sive youth did­n’t ac­tivate brain ar­e­as in­volved in self-con­trol, called the me­di­al pre­fron­tal cor­tex and the tem­poropari­etal junc­tion.

The find­ings are re­ported in the cur­rent is­sue of the re­search jour­nal Bi­o­log­i­cal Psy­chol­o­gy.

The more nor­mal youth, De­cety said, acted si­m­i­larly to youth in a study re­leased ear­li­er this year, in which his group used scans to show 7- to 12-year-olds are nat­u­rally em­pa­thet­ic to­ward peo­ple in pain. The scans showed that when the chil­dren saw an­i­ma­t­ions of some­one get hurt, the same part of the brain that reg­is­tered pain when they hurt be­came ac­tive up­on see­ing some­one else hurt, he ex­plained. When they saw some­one in­ten­tion­ally hurt, the part of the brain as­so­ci­at­ed with un­der­standing so­cial in­ter­ac­tion and mor­al rea­son­ing be­came ac­tive.


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Unusually aggressive youth may enjoy inflicting pain, researchers at the University of Chicago have found in a study using brain scans. Videos of people getting hurt were found to trigger flurries of activity in a brain area associated with reward in aggressive youth, the scientists said; other kids didn’t react that way. The research shows some aggressive youths’ natural empathetic impulse may be disrupted, said the university’s Jean Decety, who led the research. “This work will help us better understand ways to work with juveniles inclined to aggression and violence,” he added. The scientists compared eight 16- to 18-year-old boys who had shown disruptive behavior—such as starting a fight, using a weapon or stealing after confronting a victim—to adolescent boys with no unusual signs of aggression. Participants underwent brain scans while watching videos of people having their foot stepped on, having a heavy bowl fall on their hands, or the like. The scanning system was of a widely used type known as functional Magnetic Resonance Imaging, which measures brain activity based on where blood is flowing. Aggressive adolescents showed a “specific and very strong activation” in a brain area called the ventral striatum, known from previous studies to respond to pleasurable events, Decety said. Unlike the control group, he added, the more aggressive youth didn’t activate brain areas involved in self-control, called the medial prefrontal cortex and the temporoparietal junction. The findings are reported in the current issue of the research journal Biological Psychology. The more normal youth, Decety said, acted similarly to youth in a study released earlier this year, in which his group used scans to show 7- to 12-year-olds are naturally empathetic toward people in pain. The scans showed that when the children saw animations of someone get hurt, the same part of the brain that registered pain when they hurt became active upon seeing someone else hurt, he explained. When they saw someone intentionally hurt, the part of the brain associated with understanding social interaction and moral reasoning became active.