Aggression+(Bonny,+Kit,+River)

=**Topic : Are there biological factors influencing aggression and its inhibition?** = =** Introduction ** =

Aggression is something that always happens around human beings. It is a behavior that is intended to produce harm to another person, either physically or verbally (Bandura, 1978; Myers, 2002; Vasta, Miller, & Ellis, (2004), which is not only committed by individuals, but also by groups (DeWall & Anderson, 2010). What’s more, aggression remains a controversial topic within eras. For instance, which factor causes aggression? Personal? Situational? Or both? Who are more likely to act aggressively? Children? Adolescents? Adults or elderly? What are the forms of aggression?

 In this paper, we will discuss how personal and situational factors influence physical aggression (i.e. bullying) on adolescents. A significant proportion of children in adolescence has been seriously affected by bullying behavior ( e.g. Perry, Kusel, & Perry, 1988; Rigby & Slee,1993; Schuster, 1996; Smith & Shu, 2000).  Bullying often defined as ‘‘long-standingviolence, physical, or psychological, conducted byan individual or a group and directed against an individual who is not able to defend her/himself inthe actual situation’’ (Roland and Idsoe, 2001). In other words, bullying is an intentional harmful behavior with an imbalance of powerbetween victim and bully repeatedly (Salmivalli, 2010). Two common forms of bullying were teasing and hitting or kicking.  Based on Albert Bandura’s (1977) social learning theory, general aggression model (GAM) by Anderson & Bushman (2002) is introduced to discuss the factors of aggression more in depth. Biological-Situational Interaction on aggression and inhibition will also be discussed.

=**1. Aggression in Brain** = = = Coccaro et al. (2011) proposed that reactive aggression is more impulsive, which the aggressive behaviors are more situational and unpredictable, and without careful consideration or deliberate antecedent. Coccaro et al. (2011) analyze the impulsive aggression of neural system in three different dimensions, namely, 1) neural system that include subcortical regions and emotion-expression regions, 2) evaluation of consequences of aggression and 3) emotion regulation. Davidson et al. (2000) suggested orbitofrontal cortex (OFC) (Figure 1), amygdala (Figure 2) and anterior cingulate cortex (ACC) (figure 3) regulate emotions of aggression.

**__Regulation of emotion__**
Current video games are realistic and many adolescents spend much time in playing video games (Mathiak and Weber, 2006). The following video clip shows the difference in the level of realistic of violent video game plays in the year 1993 and 2008. Video 1: Violence in Video Games - Then (1993) and Now (2008) media type="youtube" key="hiMAJFjCEDI" height="315" width="560" Download: FLV MP4 3GP  Download: FLVMP43GP

The following video clip is a list of 15 most violent games (please note that the content of the video contain inappropriate content that may not be suitable for children and adolescence.) Video 2: Top 15 most violent games <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">media type="youtube" key="l9UqvVzYJbs" height="315" width="420" Download: FLV MP4 3GP <span style="display: block; font-family: 'Times New Roman',Times,serif; margin-top: 3px;"> Download: FLVMP43GP

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Hence, this section will mainly use violent video games to illustrate the relevant brain areas for aggression. <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> <span style="font-family: 'Times New Roman',Times,serif;">Figure 1 : MRI view of orbitofrontal cortex (OFC) (Wicks, 2008)

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> <span style="font-family: 'Times New Roman',Times,serif;">Figure 2: MRI coronal view of the amygdala (Rieder et al. 2011)

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> <span style="font-family: 'Times New Roman',Times,serif;">Figure 3: MRI view of anterior cingulate cortex (ACC) (Hall, 2011)

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">//__Short term effect of violent video games__// <span style="font-family: 'Times New Roman',Times,serif;">Wang et al. (2009) examine the effect of short-term exposure to violent video game on neural mechanism in adolescent. Wang et al. (2009) proposed that short-term exposure to violent video games will induce short-term change in brain function, in particular the prefrontal cortex and amygdala, which associated with executive control and regulation of affection, when comparing with the non-violent video game.

<span style="font-family: 'Times New Roman',Times,serif;">Participants were aged 13 – 17 and they were randomly assigned into groups of violent video game play and non-violent video game play, while they were instructed to play (Wang et al., 2009). Within 1 month of the first study visit, second study visit was conducted by the scanning of fMRI with tasks of Counting Stroop and Emotional Stroop (Wang et al., 2009). The random assignment and experimental control provide basis for the difference in brain function between groups were the result of the experimental condition. Emotional Stroop task asked participants to identify the ink color of the words, which indicate the violent word among the non-violent words (Wang et al., 2009).

<span style="font-family: 'Times New Roman',Times,serif;">In the Emotional Stroop task, the violent video game players showed increased activation in the bilateral ventrolateral prefrontal cortex (VLPFC), right amygdala and right lingual gyrus, which reveal greater effort in inhibiting the interference of emotional stimuli in order to achieve normal behavior performance (Wang et al., 2009).

<span style="font-family: 'Times New Roman',Times,serif;">Also, violent video game players showed decrease in activity in prefrontal cortex, namely the left dorsolateral prefrontal cortex (DLPFC), and less functional connectivity between the DLPFC and dorsal anterior cingulate cortex (ACC), which these components were activated in executive and cognitive control processing that include selective attention and response inhibition (Wang et al., 2009).

<span style="font-family: 'Times New Roman',Times,serif;">In contrast, during the Emotional Stroop task, the non-violent video game players showed deactivation of the amygdala, which reflect regulation of emotion, and there were increased activation of medial prefrontal cortex (MPFC) while violent video game players showed greater right amygdala activation (Wang et al., 2009). Hence, it demonstrated that MPFC is crucial in monitoring of emotional conflicts.

<span style="font-family: 'Times New Roman',Times,serif;">Thus, this study demonstrated that short-time video game play can induce the increased activity in brain regions relevant to arousal, anxiety, emotional reactivity and decreased activation in prefrontal regions for regulation of emotion and executive control (Wang et al., 2009). <span style="font-family: 'Times New Roman',Times,serif;">Regarding the long term effects, physiological reactivity would be decreased as a result of repeated exposure to violence in terms of time, duration and frequency of exposure (Wang et al., 2009).

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">//__Role of ventromedial prefrontal cortex and amygdala for the appropriate behvaiour of violence during video game play__// <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Amygdala is also important in social cognition and evaluation of socio-affective sensory stimuli in violent or compassionate behavior (King et al., 2006). <span style="font-family: 'Times New Roman',Times,serif;"> <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Figure 4 (King et al., 2006) <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">King et al. (2006) examined the socially appropriate behavior of neural systems through video games of healing the passive casualty (part a of figure 4) or attacking humanoid (part b of figure 4) while attacking the casualty (part c of figure 4) or healing the humanoid (part d of figure 4) were inappropriate behavior. <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Participants aged from 18 – 38 were recruited and in the virtual environment, each of them were asked to attack and heal the humanoid and human respectively, which involve 4 conditions, and their brain functions were collected by MRI (King et al., 2006). <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">The results showed that there were significant activations in the orbitofrontal / ventromedial prefrontal cortex and amygdala when appropriate behavior were involved, namely attacking the humanoid and healing human, which reflect appropriate violence and compassion respectively (King et al., 2006). This supported the argument that ventromedial prefrontal cortex and amygdala are responsible for socially appropriate behavior, and amygdala was activated in the violent condition (King et al., 2006). <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">This is consistent with the idea that amygdala is responsible for social cognition (King et al., 2006). Somatic sensory input through insula and social contextual information from orbitofrontal cortex is evaluated by amygdala, in the aspect of the prominent socio-affective sensory stimuli (King et al., 2006). <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Hence, King et al. (2006) suggested that dysfunction in these regions may result in socially inappropriate behavior and this argument was supported by Coccaro at al. (2007). Coccaro at al. (2007) suggested that dysfunction in amygdala underlie impulsive aggressive response in social provocation and hypofunction in OFC may be a common mechanism for pathophysiology of aggressive behavior.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">//__Brain activity during violent video games__// <span style="font-family: 'Times New Roman',Times,serif;">Mathiak and Weber (2006) recruited 13 male participants aged 18 – 26, who played at least 5 hours of video games per week, to participate in the study of the effect of playing violent video game (first-person shooting game) on brain activity and the brain activity was recorded by fMRI.

<span style="font-family: 'Times New Roman',Times,serif;">During violent scenes, there were strong deactivations of rostral part of anterior cingulate cortex (ACC) and activation of dorsal part of ACC, while the signal of amygdala decreases (Mathiak and Weber, 2006). This suggests active suppression of affective processing that promotes cognitive operation (Mathiak and Weber, 2006).

<span style="font-family: 'Times New Roman',Times,serif;">ACC is crucial in attention control, regulation of emotion and performance monitoring that impairment may cause aggressive behavior (Davidson et al., 2000; Mathews et al. 2005).

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">//__Summary of the effect of violent video game play__// <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">The above violent game plays studies suggest there are changes in amygdala, prefrontal cortex and cingulate cortex (Kalnin et al., 2011), while there were discrepant findings, which may be result of difference in methodology (Wang et al. 2009). <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">Though the results of amygdala seem varied that amygdala is deactivated in the violent scenes for the habitual video game players (Mathiak and Weber, 2006) while it was activated in the context of appropriated violence and prior exposure to violent content (King et al., 2006; Wang et al., 2009). Deactivation of amygdala could be viewed as regulation of emotion (Wang et al., 2009) and thus, the violent scenes of Mathiak and Weber (2006) can be interrupted as inappropriate violence and deactivation was needed. In this aspect, the result of Mathiak and Weber (2006) would be more consistent with King et al’s study (2006). <span style="font-family: 'Times New Roman',Times,serif;">//__Frontal cortex in regulation of emotion__// <span style="font-family: 'Times New Roman',Times,serif;">Lesions in the orbiofrontal cortex (OFC) and the prefrontal cortex (PFC) would induce aggression (Davidson, et al., 2000). A patient with sustained damage in bilateral OFC and some damage to left amygdala show impulsive aggression, who was never aggressive previously (Blair and Cipolotti, 2000; Davidson, et al., 2000). He was impaired in the recognition of anger and disgust, and he was hyporesponsive to threatening objects (Blair and Cipolotti, 2000; Davidson, et al., 2000). This demonstrated the importance of OFC and PFC in regulation of emotion and its importance in aggression.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">**__Brain areas for Decision making__** <span style="font-family: 'Times New Roman',Times,serif;">The above sections mainly focus on the regulation of emotion in aggression and violence.

<span style="font-family: 'Times New Roman',Times,serif;">Decision making include 1) representation of decision problem 2) selection of action based on the evaluation of action and associated possible outcomes or consequences 3) monitoring of outcomes and learning from feedback (Ernst and Paulus, 2005; Fellows, 2004; Rangel, Camerer and Montague, 2008; Coccaro et al., 2011). Coccaro et al. (2011) suggested that individuals who impaired with any of these processes are more likely to involve in aggression and he/she may fail to recognize the disadvantageous or inappropriate aggression that based on anticipated consequence, including social consequence.

<span style="font-family: 'Times New Roman',Times,serif;">Coccaro et al. (2011) proposed that orbitomedial prefrontal cortex (OMPFC) is associated with aggression and it is contribute in decision making, including moral decision making. Also, it is essential in detecting and assessing the crucial social cues and OMPFC activates in emotion-evocative cues (Phan et al., 2002; Coccaro et al., 2011). Damage to OMPFC would result in socially inappropriate behavior and found to be associated with aggressive behavior (Volvaka, 1995; Grafman et al. 1996; Coccaro et al., 2011).

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">**__Summary of Brain areas for aggression__** <span style="font-family: 'Times New Roman',Times,serif;">The importance of orbitofrontal cortex (OFC), amygdala and anterior cingulate cortex (ACC) in regulation of emotions for aggression was demonstrated through the video violent game play and the lesion of OFC and the importance in decision making was illustrated through orbitomedial prefrontal cortex (OMPFC).

<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Kit, Lau Chiu Kit (09921040t)

=<span style="font-family: 'Times New Roman',Times,serif;">**2. Aggression in** **neurotic** **level** =

<span style="font-family: 'Times New Roman',Times,serif;">After the discussion about the brain-behavior association on aggression, in behavioral endocrinology and cognitive neuroscience will focus on the effects of specific biological factors influences aggression behavior, such as hormones. In the following, we will discuss which parts in our neural system contribute to aggressive behavior. <span style="font-family: 'Times New Roman',Times,serif;">From the human studies investigated about the biological signals linked to aggression, several important signaling molecules have demonstrated can affect aggression, for example, from rats experiment; Ferrari, P. F. et al. (2007) found that increase dopamine secretion is significantly anticipating in the interactions of aggression. And Clement, J. et al. (1987) noticed that the transmitter called GABA plays an important role in the control of aggressive behavior, the aggressive mice are characterized by the lower GABA levels in amygdale. (Reviewed in Nelson, R. J., & Trainor, B. C., 2007) In this essay, we will focus more on the neural mechanisms of testosterone related in the aggression.

<span style="font-family: 'Times New Roman',Times,serif;">//__Testosterone__// <span style="font-family: 'Times New Roman',Times,serif;">Testosterone acts on estrogen receptors when converted into estradial by the enzyme aromatase. (Fig. 4) The process of aromatization and the activity of the estrogen receptors in the hypothalamic area mediated aggressive behavior. (Schlinger B.A., 1989, 1990). <span style="font-family: 'Times New Roman',Times,serif;"> <span style="font-family: 'Times New Roman',Times,serif;">Fig 5. The chemical structures of testosterone and its derivatives are shown. Testosterone is converted into 5a-DHT by the enzyme 5a- reductase to then act on androgen receptors. Alternatively, aromatase can convert testosterone into estradiol which acts on estrogen receptors. From Simpson, K. (2001). The Role of Testosterone in Aggression. McGill Journal of Medicine, 6, 32-40, Fig.1)

<span style="font-family: 'Times New Roman',Times,serif;">There is a critical period for the testosterone to sensitize neural circuits. The male mice being castration at birth shown less fighting levels compared with whom being castrate on day 10. The latter have longer injection of testosterone and androgen stimulation in the critical period. (Fig 5.) (Bronson F.H., Desjardins C. 1969; Resko J.A., Feder H.H., 1968). <span style="font-family: 'Times New Roman',Times,serif;"> <span style="font-family: 'Times New Roman',Times,serif;">Fig 6. Testosterone Effects on Aggression in Male Mice (From [] ) <span style="font-family: 'Times New Roman',Times,serif;">Studies with animals have empirically demonstrated that a testosterone may play an important part in the control of aggressive behaviors. Especially from research conducted on a variety of the monogamous bird species, the researchers found a relationship in which testosterone levels may be both the cause and consequence of aggressive behavior. (Wingfield et al., 1990, 2000, 2001; Wingfield, 1985; Vleck and Brown, 1999) Such as the studies of the song sparrow and white-crowned sparrows, Male birds show testosterone levels rise throughout the breeding season and these levels support them to face to challenges of mating and reproduction in which increase their readiness to fight. This hypothesis not only applied in the bird species, but also in the fish and rats. Give daily injection of testosterone in the rates was increased their aggressiveness (Archer, 1988; Edwards D.A. 1969). The researcher Edward Kravitz and his colleagues tried to investigate how the aggression is brought about in the nervous system by observing aggression in the lobster and flies. They keep the lobster separately to make sure all lobsters have clear history of fighting. In the following video (from 3:01 to 5:08), we can see how the lobsters showed the testosterone influencing their aggressive behavior.

<span style="font-family: 'Times New Roman',Times,serif;">Video 3: The influence of aggressive behavior by the level of testosterone on lobsters. <span style="font-family: 'Times New Roman',Times,serif;">media type="youtube" key="R_qDfteRQ2g?rel=0" height="384" width="512" Download: FLV MP4 3GP <span style="display: block; font-family: 'Times New Roman',Times,serif; margin-top: 3px;"> Download: FLVMP43GP

<span style="font-family: 'Times New Roman',Times,serif;">However, the concerns of psychologists is may this challenge hypothesis able to be extended to apply to explain the aggressive behaviors of human. Some studies shown the level of testosterone is a moderated factor of aggression in both men and women. (Wirth, M., and Schultheiss, O., 2007; Archer, J. et al., 2005; OʼConnor, D. B. et al., 2004; Pope, H. G. et al., 2000; Archer, J. et al., 1998; Finkelstein, J. W., 1997 ). Testosterone is specifically involving in the control of impulsive aggression in response to social threat (Mazur & Booth, 1998). <span style="font-family: 'Times New Roman',Times,serif;">Sanchez-Martin and his colleagues (2011) investigated the relationship between the androstenedione and testosterone levels in relation to the different form of aggression in 90 adolescents. By using a peer rating technique to measure the level of physical, verbal and indirect aggression and collected the saliva samples to measure the level of testosterone and androstenedione, the researcher found that statistically significant effect of this two androgens on aggression, especially in physical aggression, and is consistent with the previous studies. The researcher also found an interaction between state anger and testosterone on the verbal aggression (Fig. 6) and an interaction between state anger and androstenedione on the physical aggression. <span style="font-family: 'Times New Roman',Times,serif;">Fig. 7 Interaction between testosterone and state anger in verbal aggression. <span style="font-family: 'Times New Roman',Times,serif;">// (From Sanchex-Martin, J. R., Azurmendi, A., Pasual-Sagastizabal, E., Cardas, J., Braza, F., Braza, P., Carreras, M. R., Munoz, J. M. (2011). Androgen levels and anger and impulsivity measures as predictors of physical, verbal and indirect aggression in boys and girls. Psychoneurondocrinology, 36, 75-760, Fig. 3) // <span style="font-family: 'Times New Roman',Times,serif;">__//GABA and testosterone//__ <span style="font-family: 'Times New Roman',Times,serif;">As mentioned in the previous paragraph, low GABA level mice have higher frequency of aggressive behavior. Earley and Leonard (1976) found mice with the treatment of testosterone decreased the concentration of GABAA receptors in particular brain area and exhibited less aggressive attacks.

<span style="font-family: 'Times New Roman',Times,serif;">//__Orbitofrontal Cortex (OFC)__//

<span style="font-family: 'Times New Roman',Times,serif;">In order to explain the effect of testosterone on aggression in neural mechanism, Mehta and Beer (2009) hypnotized the effect of testosterone on aggression was mediated by the decreased activity in the Orbitofrontal Cortex (OFC). Participants were have saliva samples and scanned with fMRI while playing the ultimatum game (for more details, see []), the choice of the participant make between aggression or monetary reward will be analyze. In the experiment conducted in the chimpanzees (See video 1, 2, from []), they are more easily to accept an unfair deal. However, in the study of human, the responders report feeling angry after being treated unfair and increased tendency to reject unfair offers (i.e., aggressive behavior) (vanʼt Wout et al. 2006; Pillutla and Murnighan, 1996). By the observation of Mehta and Beer, they found that a hormone-brain-behavior relationship, testosterone regulated aggressive behavior by reduced the activation of the medical OFC, a region for impulse control and self-regulation.

<span style="font-family: 'Times New Roman',Times,serif;">Video 4: Chimpanzese accepting an unfair (8/2) offer <span style="font-family: 'Times New Roman',Times,serif;">media type="youtube" key="-2oOR-7pe-Q?rel=0" height="383" width="511" Download: FLV MP4 3GP <span style="display: block; font-family: 'Times New Roman',Times,serif; margin-top: 3px;"> Download: FLVMP43GP

<span style="font-family: 'Times New Roman',Times,serif;">Video 5: Chimpanzese rejecting a hyperunfair (10/0) offer <span style="font-family: 'Times New Roman',Times,serif;">media type="youtube" key="ENSwMdblShw?rel=0" height="384" width="512" Download: FLV MP4 3GP <span style="display: block; font-family: 'Times New Roman',Times,serif; margin-top: 3px;"> Download: FLVMP43GP

<span style="font-family: 'Times New Roman',Times,serif;">//__Inhabitation of aggression - Fadrozole__// <span style="font-family: 'Times New Roman',Times,serif;">Expect the activity of OFC modulate aggressive behavior, fadrozole (an aromatase inhibitor) showed the effect to reduce the aggressive behavior in the mice by inhibited the estrogen receptor alaha (ERα). (Trainor, B. C., Greiwe, K. M., Nelson, R. J., 2006). An osmotic minipump filled with fadrozole (0.25mg/kg) given to 12 castrated mices. In this hormone manipulation experiment, fadrozole showed empirically reduced the number of bites compared to other-treated mices.

<span style="font-family: 'Times New Roman',Times,serif;">//__Discussion on the relationship between the aggressive and testosterones__// <span style="font-family: 'Times New Roman',Times,serif;">However, there still are some questions about the relationship between the aggressive and testosterones have to be answer in the further researchers. First, based on the greatly increase of testosterone level went through puberty (Halpern et al. 1994), and the observation of boy is more likely to involve in physical bullying (Olweus, 1978; Felix and McMahon, 2006), some researchers predicted aggression is increased in male during puberty (Halpern et al. 1994). However, Archer (2004) conducted a series of meta- analyses and found no pronounced increases of the aggressive behavior of boys at puberty. Or this result showed the genetic-environment interaction of the bullying behavior? As most studies of human aggression showed the effect of testosterone is context-dependent. (In the following paragraph, the topic will be discussed in details.) The role of testosterones in the puberty stage is still in doubt. <span style="font-family: 'Times New Roman',Times,serif;">Bonny, Law Sin Wan (08619976t)

=<span style="font-family: 'Times New Roman',Times,serif;">**3. Social Determinants of Aggression** =

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">//__General Aggression Model (GAM; Anderson & Bushman, 2002)__// <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> General aggression model (GAM; Anderson & Bushman, 2002) is built on Albert Bandura’s social learning perspective, which explained the factors that cause aggression. (DeWall &Anderson, 2010).

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> As Bandura (1977) said, “most human behavior is learned observationally through modeling: from observing others one forms an idea of how new behaviors are performed, and on later occasions this coded information serves as a guide for action” (p.22) GAM provides a more complete account of the foundations of human aggression. <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> According to GAM (Fig. 8.1), there are two different types of input variables: personal and situational. Personal factors include an individual’s traits, attitudes, beliefs, knowledge structures and biological factors while provocation involved in situational variables.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> These two different variables will then lead to aggression through their impact on the three basic processes: arousal, affective states and cognitions. In the process of arousal, people may increase their physiological arousal or excitement. For the affective states, people provoke aggressive feelings and noticeable signs of that feeling. For example, someone shows the angry facial expression. Through cognition, we can stimulate individuals to think aggressive thoughts or bring the beliefs and attitudes towards aggression to mind.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> Then, appraisal and decision processes depend on the individual’s interpretations of the current situation and knowledge structures, they engage either in thoughtful action or impulsive action. People who engage in thoughtful action may repress their anger while those engage in impulsive action may lead to aggressive behaviors.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> As discussed above, provocation is one of the situational factors that lead to human aggression. Provocation means “actions by others that tend to trigger aggression in the recipient, often because these actions are perceived as stemming from malicious intent” (Baron, Byrne, & Branscombe, 2006, p. 426) which are more likely to arouse anger. Therefore, the likelihood that the recipient will take revenge by aggression is very high. Physical attack such as fighting is a kind of provocation.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> In short, the interaction between personal and situational inputs activates affective, arousal, and cognitive internal states, which in turn influence aggression by means of appraisal and decision processes. <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> Additionally, GAM also makes further predictions about aggression between groups of people that consists of two or more people with a defined identity and common goal. Increased levels of aggressive affect, arousal, or cognition and interact with an unfriendly group increases hostile expectations (Hoyle, Pinkley, & Insko, 1989; Zajonc, 1965) which heightened aggression between groups (relative to individuals). This is consistent with Meier, Hinsz, and Heimerdinger’s (2007) finding that groups are more likely to commit and receive aggression than individuals. When the group size is larger, the level of aggression will increase.

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;"> //__Social Learning Theory --- Albert Bandura (1961, 1969, 1973, 1977, 1978).__// <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">As Bandura (1977) proposed a social learning theory of aggression, people’s aggressive behaviour is learned by observing others. In 1961, Bandura conducted a “Bobo” doll experiment with others (Bandura, Ross & Ross, 1961) to examine whether children perform aggressive behavior by modeling or not. The results have shown that subjects who observed the nonaggressive models were generally less aggressive. Therefore, aggression shaped through the learning processes.

<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Equally important, direct reinforcement would foster aggression. Direct reinforcement refers to the external consequences for an individual's action. (Bandura, 1969). An individual’s aggressive reactions are significantly related to reinforcement from peers for both in physical and relational aggression (Werner and Crick, 2004).

<span style="color: black; font-family: 'Times New Roman',Times,serif; text-align: justify;">Furthermore, vicarious reinforcement would also increase aggression. Direct observation of a peer's reinforcement is a type of vicarious reinforcement. (Bandura, 1973, 1978). Consequences obtained by peers usually play a role in determining whether an individual’s will commit the same act or not. In the condition of aggression, aggression may be prevented if an individual witnesses a punishment he or she dislikes to receive. On the contrary, if there was no consequence, or the peer’s aggressive behavior is rewarded, the individual may be more likely to commit the same act (Bandura, 1973, 1978).

<span style="font-family: 'Times New Roman',Times,serif;">//__Peer Group Influences on Aggression --- Deindividuation, Conformity (to peer norms) and Social Identity__//
<span style="font-family: 'Times New Roman',Times,serif;">__**Definition of A Group**__

<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Marvin Shaw (1981) and John Turner (1987) indicated that a group consists of two or more people with interaction and influence on one another and view themselves as “us” As Hartup (1983) described, in a group: “social interaction occurs regularly, values are shared over and above those maintained in society at large, individual members have a sense of belonging, and a structure exists to support the attitudes that members should have toward one another” (p. 144). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">In other words, the need to belong is essential for human (Baumesiter & Leary, 1995). Groups serve as a source of self-identity and achieve a common goal (Vasta, Miller, & Ellis, 2004). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">According to Erikson (1968), peer influence is important in adolescence as an individual strives for identity. Thus, an adolescent’s behavior and conceptualization is mainly influenced by the peer group involved. <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Bullying is a form of negative influence (Espelage, Holt, & Henkel, 2003). that demonstrated “peer group power” in which all the group member fulfilling different roles as victim, bully, reinforcer of the bully, assistant of the bully, defender of the victim, and outsider ( Salmivalli, Lagerspetz, Bjo¨rkqvist, O¨ sterman, & Kaukiainen, 1996).

<span style="font-family: 'Times New Roman',Times,serif;">//__Conformity (to peer norms)__//
<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Conformity is a situational factor that leads to human aggression. It is one of the social influences. “Conformity is best explained in relation to peer pressure, especially when large group of people hold the same opinion and beliefs” (Warwick & Bolton, 2004, p.227). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">In other words, informational influence (the desire to be right) and normative influence (the desire to be accepted and to avoid rejection form others) lead us to confirm (Morton Deutsch and Harold Gerard, 1955). In order to meet the need of belonging, an individual’s public behavior and private attitudes and beliefs are affected by group norms **(**Burns, Maycock, Cross & Brown, 2008; Poteat & Spanierman, 2010 ). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Norms prescribed “proper” behavior, which were understood rules for accepted and expected behavior for every group member (Turner, Hogg, Oakes, Reicher, & Wetherell, 1987). Accordingly, violation of norms is unacceptable among group members (Abrams & Hogg, 1990; Hogg & Turner, 1987; Ojala & Nesdale, 2004; Turner, 1991). Group norms can be seen as a way for improving the group’s status and power (Emler & Reicher, 1995; Tajfel & Turner, 1979). Individuals who are strong identified with their group would ignore own values (Diener, 1980). Thus, conformity is highest if an individual with cohesiveness (A “we feeling”) and unanimity (Abrams & others, 1990; Hogg & others, 1990). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">As in the movie, Danger Encounter, those adolescents organized as a group named “A Strong Rock” with group norms, which is mainly focused on all member’s loyalty to the group. ([] 03:58~05:20). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">However, bullying is misperceptions of norms among peer group members that lead them to act accord with the adhered norm (Perkins, Craig, & Perkins, 2011). As a result, an adolescent who bullies joins other bullies or reinforces or assists in bullying Salmivalli, Huttunen, & Lagerspetz, 1997 ).

<span style="font-family: 'Times New Roman',Times,serif;">//__Deindividuation (Leon Festinger, Albert Pepitone, and Theodore Newcomb (1952)__//
<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Besides conformity, deindividuation is another factor that leads to human aggression. As Leon Festinger, Albert Pepitone, and Theodore Newcomb (1952) said, people may lose self-awareness and evaluation apprehension in a group situation since they foster responsiveness to group norms either good or bad. As a result, deindividuation resulted from a loss of individuality and self-control. <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">When being with the group, people do not feel much responsibility since “everyone is doing it”. Consequently, there is a positive relationship between group size and deindividuation. Deindividuation increases when people perceive the action as the group’s (Zimbardo, 1970). As an illustration, aggressive reactions such as bullying intensified through group interaction due to diffusing responsibility (Lagerspetz & others, 1982). <span style="font-family: 'Times New Roman',Times,serif;">For example, as the movie, Danger Encounter demonstrated members in “A Strong Rock” retaliated by physical attack such as hitting a triad’s leader. Their aggression is encouraged by deindividuation since their aggressive behavior is less accountable as individual’s ([] 09:42~12:17).

<span style="font-family: 'Times New Roman',Times,serif;">//__Social Identity Theory (Tajfel, 1982; Tajfel & Turner, 1979).__//
<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">As Tajfel defined, social identity is ‘‘that part of an individual’s self concept which derives from his knowledge of his membership in a social group (or groups) together with the value and emotional significance attached to that membership’’ (1981, p. 255). Therefore, adolescents who feel positive and with a sense of belonging about their own group will be more likely to adopt, even internalize the group’s attitudes and values as their own. (Ojala & Nesdale, 2004).

<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">Due to the increase of conformity to group norms and deindividuation, in-group favouritism and bias enhanced (Brown & Abrams, 1986; Diehl, 1988; Jetten, Spears, & Manstead, 1996, 1997a; staub, 1996; Tajfel & Turner, 1986) to distinguish an individual’s group (in group) from other groups (out group) (Gini, 2006; Ojala & Nesdale, 2004).

<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">As an illustration, in the movie, Danger Encounter, all group members in the “A Strong Rock” deserved a sense of belonging which enhanced their in-group / out-group contrast. ([] 21:54~22:59). Yet, such sense of belonging in the group which aggression is valued, which in turn lead to an increased tendency to engage in aggressive reactions. Hence, those adolescents tend to be more willing to commit bullying. (Perkins, Craig, & Perkins, 2011) because of the adherence to the group’s conduct norms and the internalization of the group’s values (Lim & Chang, 2009).

<span style="font-family: 'Times New Roman',Times,serif;">This is especially true if an adolescent with strong group identity and believe the group’s status is being threatened by “out-group” members, bullying is an acceptable and normative behavior in order to maintain or increase the positive distinctiveness within the group (Gini, 2006). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">In short, aggression is built on situational factors included provocation, learning, conformity to peer norms, deindividuation and social identity. Within group interaction, aggression increased due to diffusing responsibility (Anderson & Bushman, 1997; Bushman & Anderson, 1998). <span style="font-family: 'Times New Roman',Times,serif; text-align: justify;">In my opinion, conformity, deindividuation and social identity should also be included under the situational variables since they are the main factors that people to perform aggressive behavior. (Fig. 8.2) Additionally, conformity is neither all bad nor all good. We could enjoy being with the group, yet self-awareness and individuality should still be noted.

<span style="font-family: 'Times New Roman',Times,serif; text-align: justify;"> <span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">River, Ho Chi Ki (08618642t)

<span style="display: block; font-family: 'Times New Roman',Times,serif; text-align: justify;">**Conclusion** <span style="font-family: 'Times New Roman','serif'; text-align: justify;">Physical aggression is merely the expression of bullying that may be resulted from prolonged exposure to violent video game play, which reduces adolescent’s physiological reactivity towards violence (Wang et al., 2009). Also, Davidson et al. (2000) proposed that impulsive and affective aggression may be the result of failure in emotion regulation. Individuals predispose to aggression and violence may have the abnormality in the relevant brain areas, while normal individuals can voluntarily regulate their emotions from the restraint-producing cues in the environment (Davidson et al., 2000). According to the meta-analyses conducted by Arthur (2004), the greatly increase of testosterone at the puberty stage did not markedly rise the frequency of aggression. One possible explanation is that the effect of testosterone in aggression is context-dependent. In other words, bullying is prominent in adolescence that biological factors alone cannot fully explain the scenario since human beings are social creatures. The genetic and social factors interacted as the following: <span style="font-family: 'Times New Roman','serif'; text-align: justify;">During adolescence, peer influence is essential to strive for identity (Erikson, 1968). The need to belong leads individuals’ behavior and attitude affected by conformity to group norm (Burns, Maycock, Cross & Brown, 2008; Poteat & Spanierman, 2010). When people perceive the action as the group’s, deindividuation increases (Zimbardo, 1970). Due to the increase of conformity to group norms and deindividuation, in-group favouritism and bias enhanced (Brown & Abrams, 1986; Diehl, 1988; Jetten, Spears, & Manstead, 1996, 1997a; staub, 1996; Tajfel & Turner, 1986). <span style="font-family: 'Times New Roman','serif'; text-align: justify;">All in all, both biological factors and social factors have impact on human aggression.
 * <span style="font-family: 'Times New Roman','serif'; text-align: justify;">Genes/Prenatal influences || à || <span style="font-family: 'Times New Roman','serif'; text-align: justify;">Increase of some tendency ||
 * ||  || <span style="display: block; font-family: 'Times New Roman','serif'; text-align: center;">↑↓ ||
 * ||  || <span style="font-family: 'Times New Roman','serif'; text-align: justify;">Environment that facilitates ||

<span style="font-family: 'Times New Roman',Times,serif;">**__Reference:__**

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