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Posts Tagged ‘aggression

Ninja Mickey – Agression Proves Rewarding For Mice Brains

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New research from Vanderbilt University shows for the first time that the brain of mice processes aggression as a reward – much like sex, food and drugs – offering insights into our propensity to fight and our fascination with violent sports like boxing and football or violent media represenatations.
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“Aggression occurs among virtually all vertebrates and is necessary to get and keep important resources such as mates, territory and food,” Craig Kennedy, professor of special education and pediatrics, said. “We have found that the ‘reward pathway’ in the brain becomes engaged in response to an aggressive event and that dopamine is involved.”“It is well known that dopamine is produced in response to rewarding stimuli such as food, sex and drugs of abuse,” Maria Couppis, who conducted the study as her doctoral thesis at Vanderbilt, said. “What we have now found is that it also serves as positive reinforcement for aggression.”

For the experiments, a pair of mice – one male, one female – was kept in one cage and five “intruder” mice were kept in a separate cage. The female mouse was temporarily removed, and an intruder mouse was introduced in its place, triggering an aggressive response by the “home” male mouse. Aggressive behavior included tail rattle, an aggressive sideways stance, boxing and biting.

The home mouse was then trained to poke a target with its nose to get the intruder to return, at which point it again behaved aggressively toward it. The home mouse consistently poked the trigger, which was presented once a day, indicating it experienced the aggressive encounter with the intruder as a reward.

The same home mice were then treated with a drug that suppressed their dopamine receptors. After this treatment, they decreased the frequency with which they instigated the intruder’s entry.

In a separate experiment, the mice were treated with the dopamine receptor suppressors again and their movements in an open cage were observed. They showed no significant changes in overall movement compared to times when they had not received the drugs. This was done to demonstrate that their decreased aggression in the previous experiment was not caused by overall lethargy in response to the drug, a problem that had confounded previous experiments.

The Vanderbilt experiments are the first to demonstrate a link between behavior and the activity of dopamine receptors in response to an aggressive event.

“We learned from these experiments that an individual will intentionally seek out an aggressive encounter solely because they experience a rewarding sensation from it,” Kennedy said. “This shows for the first time that aggression, on its own, is motivating, and that the well-known positive reinforcer dopamine plays a critical role.”

Kennedy is chair of Vanderbilt’s Peabody College of education and human development’s special education department, which is consistently ranked as the top special education program in the nation. He is also director of the Vanderbilt Kennedy Center for Research of Human Development’s Behavior Analysis Clinic.

Psychopharmacology (Berl). 2008 Jan 8 [Epub ahead of print]
The rewarding effect of aggression is reduced by nucleus accumbens dopamine receptor antagonism in mice.

Vanderbilt Kennedy Center, Vanderbilt University, Nashville, TN, 37204, USA.

RATIONALE: Dopamine (DA) receptors within the nucleus accumbens (NAc) are implicated in the rewarding properties of stimuli. Aggressive behavior can be reinforcing but the involvement of NAc DA in the reinforcing effects of aggression has yet to be demonstrated. OBJECTIVE: To microinject DA receptor antagonists into the NAc to dissociate their effects on reinforcement from their effects on aggressive behavior and general movement. MATERIALS AND METHODS: Male Swiss Webster mice were implanted with guide cannulae aimed for the NAc and tested for aggressive behavior in a resident-intruder procedure. Aggressive mice were then conditioned on a variable-ratio 5 (VR-5) schedule with presentation of the intruder as the reinforcing event. The D1- and D2-like receptor antagonists SCH-23390 and sulpiride were microinfused (12-50 ng) before the mice responded on the VR-5 schedule and attacked the intruder. Open-field activity was also determined following the highest doses of these drugs. RESULTS: SCH-23390 and sulpiride dose-dependently reduced VR responding but did not affect open-field activity. The 50-ng SCH-23390 dose suppressed response rates by 40% and biting behaviors by 10%; other aggressive behaviors were not affected. The 25 and 50 ng sulpiride doses almost completely inhibited VR responding; the 50-ng dose suppressed biting by 50%. CONCLUSIONS: These results suggest that both D1- and D2-like receptors in the ventral striatum are involved in the rewarding properties of aggression, but that D1-like receptors may be related to the motivation to earn reinforcement as opposed to aggressive behavior.

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Written by huehueteotl

January 16, 2008 at 11:32 am

Humor Develops From Aggression Caused By Male Hormones, Dermatologist Says

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Humour appears to develop from aggression caused by male hormones, according to a “study” published in the Christmas issue of the British Medical Journal. This respectable periodical has lately lost it’s taste for logic or has developed a taste for Christmas-hoaxes. The humorous rather than scientific report is funny reading and a beautiful demonstration of logical fallacies. 

Man on a unicycle. A professor who rode around on a unicycle noted that about two thirds of men’s ‘comic’ responses to him referred to the number of wheels – “Lost your wheel?”, for example. The professor also noticed the male response differed markedly with age. (Credit: iStockphoto/Mary Gascho)

Professor Sam Shuster observed for one year how people reacted to him as he unicycled through the streets of Newcastle upon Tyne. After some 400 anecdotical observations he concluded that he received stereotypical and predictable responses and that they must be indicative of an underlying biological phenomenon – nice chain of logically faulty conclusions (non sequitur). The results he published are amusing anyway.

Over 90% of people responded physically, for example with an exaggerated stare or a wave. Almost half responded verbally — more men than women. Here, says Professor Shuster, the sex difference was striking. 95% of adult women were praising, encouraging or showed concern. There were very few comic or snide remarks. In contrast, only 25% of adult men responded as did the women, for example, by praise or encouragement; instead 75% attempted comedy, often snide or combative as an intended put-down.

Equally striking, he says, was the repetitive and predictable nature of the comments from men; two thirds of their ‘comic’ responses referred to the number of wheels – “Lost your wheel?”, for example.

Professor Shuster also noticed the male response differed markedly with age, moving from curiosity in childhood (years 5-12) — the same reaction as young girls, – to physical and verbal aggression in boys aged 11-13 who often tried to get him to fall off the unicycle.

Responses became more verbal during the later teens, turning into disparaging ‘jokes’ or mocking songs. This then evolved into adult male humour — characterized by repetitive, humorous verbal put-downs concealing a latent aggression. Young men in cars were particularly aggressive. Professor Shuster notes that this is the age when men are at the peak of their virility. The ‘jokes’ were lost with age as older men responded more neutrally and amicably with few attempts at a jovial put-down.

The female response by contrast, was subdued during puberty and late teens — normally either apparent indifference or minimal approval. It then evolved into the laudatory and concerned adult female response.

The idea that unicycling is intrinsically funny does not explain the findings, says Professor Shuster, particularly the repetitiveness, evolution and sex differences. Genetics may explain the sex difference but not the waxing and waning of the male response. He says the simplest explanation for this change is the effect of male hormones such as testosterone, known collectively as androgens, which induce virility in men. What looks like elegant Ockham’s razor, means in fact begging the question – the easiest explanation for all of Professor Shusters observations is, that they are contingent, and anything beyond belongs into the realm of statistics of small numbers.

His further observations that initial aggressive intent seems to become channeled into a verbal response which pushes it into a contrived, but more subtle and sophisticated joke, so that the aggression would be hidden by wit, can be found, together with more sound considerations in Freud’s „Der Witz und seine Beziehung zum Unbewussten“ (1905).

BMJ 2007;335:1320-1322 (22 December), doi:10.1136/bmj.39414.552060.BE
Retirement
Sex, aggression, and humour: responses to unicycling

Sam Shuster, honorary consultant, emeritus professor of dermatology

1 Department of Dermatology, Norfolk and Norwich University Hospital, Norwich NR4 7UY

sam@shuster.eclipse.co.uk

Sam Shuster compares men and women’s responses to the sight of a unicyclist

After retiring from a busy university department in Newcastle upon Tyne, and with the time and the need for more than the usual consultancies, I was able follow some of my more extreme inclinations. As a cyclist, I had occasionally thought of using more or fewer wheels, but it was only when choosing a grandson’s gift that I got seriously lost in contemplation of a gleaming chrome unicycle. My wife said “buy the bloody” thing, which I did on the whim of the moment. After months of practice at home, I graduated to back streets, a small paved park, and finally town roads. I couldn’t avoid being noticed; in turn, I couldn’t avoid observing the form that notice took. Because at the time there were no other unicyclists in the area, such sightings would have been exceptional, yet I soon found that the responses to them were stereotyped and predictable. I realised that this indicated an underlying biological phenomenon and set about its study.

Written by huehueteotl

December 28, 2007 at 1:22 pm

Violent TV, Games Pack A Powerful Public Health Threat

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Watching media violence significantly increases the risk that a viewer or video game player will behave aggressively in both the short and long term, according to a University of Michigan study published today in a special issue of the Journal of Adolescent Health.

The study, by L. Rowell Huesmann, reviews more than half a century of research on the impact of exposure to violence in television, movies, video games and on the Internet.

“The research clearly shows that exposure to virtual violence increases the risk that both children and adults will behave aggressively,” said Huesmann, the Amos N. Tversky Collegiate Professor of Communication Studies and Psychology, and a senior research scientist at the U-M Institute for Social Research (ISR).

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In his article, Huesmann points out that U.S. children spend an average of three to four hours a day watching television. “More than 60 percent of television programs contain some violence,” he said, “and about 40 percent of those contain heavy violence.

“Children are also spending an increasingly large amount of time playing video games, most of which contain violence. Video game units are now present in 83 percent of homes with children,” he said.

According to research conducted by Huesmann and ISR colleague Brad Bushman, media violence significantly increases the risk that both children and adults will behave aggressively.

How significantly?

“Exposure to violent electronic media has a larger effect than all but one other well-known threat to public health. The only effect slightly larger than the effect of media violence on aggression is that of cigarette smoking on lung cancer,” Huesmann said.

“Our lives are saturated by the mass media, and for better or worse, violent media are having a particularly detrimental effect on the well-being of children,” he said.

“As with many other public health threats, not every child who is exposed to this threat will acquire the affliction of violent behavior. But that does not diminish the need to address the threat — as a society and as parents by trying to control children’s exposure to violent media to the extent that we can.” The reading is clearly indebted to the author’s piagetian concepts about psychosocial development. But even in the light of a Vygotskian “zone of proximal development”, narrative constructivism or REBT, the social consequences of these findings would not be any less concerning.

Dev Psychol. 2007 Jul;43(4):1038-44.

I wish I were a warrior: the role of wishful identification in the effects of violent video games on aggression in adolescent boys.

Konijn EA, Bijvank MN, Bushman BJ.

Department of Communication Science, VU University Amsterdam, Amsterdam, Netherlands. ea.konijn@fsw.vu.nl

This study tested the hypothesis that violent video games are especially likely to increase aggression when players identify with violent game characters. Dutch adolescent boys with low education ability (N=112) were randomly assigned to play a realistic or fantasy violent or nonviolent video game. Next, they competed with an ostensible partner on a reaction time task in which the winner could blast the loser with loud noise through headphones (the aggression measure). Participants were told that high noise levels could cause permanent hearing damage. Habitual video game exposure, trait aggressiveness, and sensation seeking were controlled for. As expected, the most aggressive participants were those who played a violent game and wished they were like a violent character in the game. These participants used noise levels loud enough to cause permanent hearing damage to their partners, even though their partners had not provoked them. These results show that identifying with violent video game characters makes players more aggressive. Players were especially likely to identify with violent characters in realistic games and with games they felt immersed in. Copyright 2007 APA.

see also:

Arch Pediatr Adolesc Med. 2006 Apr;160(4):348-52.

Short-term and long-term effects of violent media on aggression in children and adults.

Bushman BJ, Huesmann LR.

Vrije Universiteit, Amsterdam, the Netherlands. bbushman@umich.edu

OBJECTIVES: To test whether the results of the accumulated studies on media violence and aggressive behavior are consistent with the theories that have evolved to explain the effects. We tested for the existence of both short-term and long-term effects for aggressive behavior. We also tested the theory-driven hypothesis that short-term effects should be greater for adults and long-term effects should be greater for children. DESIGN: Meta-analysis. PARTICIPANTS: Children younger than 18 years and adults. MAIN EXPOSURES: Violent media, including TV, movies, video games, music, and comic books. MAIN OUTCOME MEASURES: Measures of aggressive behavior, aggressive thoughts, angry feelings, physiological arousal (eg, heart rate, blood pressure), and helping behavior. RESULTS: Effect size estimates were combined using meta-analytic procedures. As expected, the short-term effects of violent media were greater for adults than for children whereas the long-term effects were greater for children than for adults. The results also showed that there were overall modest but significant effect sizes for exposure to media violence on aggressive behaviors, aggressive thoughts, angry feelings, arousal levels, and helping behavior. CONCLUSIONS: The results are consistent with the theory that short-term effects are mostly due to the priming of existing well-encoded scripts, schemas, or beliefs, which adults have had more time to encode. In contrast, long-term effects require the learning (encoding) of scripts, schemas, or beliefs. Children can encode new scripts, schemas, and beliefs via observational learning with less interference and effort than adults.

This one is interesting too and explains a good part of actual Bush administration’s foreign politics:

Psychol Sci. 2007 Mar;18(3):204-7.

When god sanctions killing: effect of scriptural violence on aggression.

Bushman BJ, Ridge RD, Das E, Key CW, Busath GL.

Institute for Social Research, University of Michigan, 426 Thompson St., Ann Arbor, MI 48106, USA. bbushman@umich.edu

Violent people often claim that God sanctions their actions. In two studies, participants read a violent passage said to come from either the Bible or an ancient scroll. For half the participants, the passage said that God sanctioned the violence. Next, participants competed with an ostensible partner on a task in which the winner could blast the loser with loud noise through headphones (the aggression measure). Study 1 involved Brigham Young University students; 99% believed in God and in the Bible. Study 2 involved Vrije Universiteit-Amsterdam students; 50% believed in God, and 27% believed in the Bible. In Study 1, aggression increased when the passage was from the Bible or mentioned God. In Study 2, aggression increased when the passage mentioned God, especially among participants who believed in God and in the Bible. These results suggest that scriptural violence sanctioned by God can increase aggression, especially in believers.

Written by huehueteotl

November 30, 2007 at 1:04 pm