18

Callous/Malice

An Examination of Desensitizing and Aggression-Causing Media Effects

Ron Leone and Angela Paradise

Key Outcomes of Media Violence

Startling statistics have been published on the number of violent and aggressive acts committed in the United States. According to the FBI (2010), more than 1.3 million violent crimes (e.g., murder, forcible rape, robbery, and aggravated assault) occurred in the United States in 2009. That same year, the Bureau of Justice Statistics (2009), which collects data on reported and unreported crime from the victim's perspective, measured approximately 4.3 million nonfatal violent victimizations of people age 12 or older. The Centers for Disease Control (CDC) (2008) reported that homicide continues to be the second leading cause of death for youth ages 10- to 24-years-old. Meanwhile, nationwide surveys found that nearly 20% of students reported being bullied on school property (CDC, 2010) and over 70% of teenagers have been “cyber-bullied” within the last school year (Juvonen & Gross, 2008).

What factors contribute to the wide range of violent and aggressive acts that pervades the United States? To be clear, most social scientists agree that no single variable causes a person to engage in violent or aggressive behavior. Rather, a host of factors, including psychological and cognitive impairments, parental upbringing, drug use, and access to weapons has been linked to real-world violence and aggression. Yet, we must also consider our media landscape, which, as the title of our chapter indicates, is permeated by malicious acts of violence committed by television, film, and videogame characters, often portrayed as callous and indifferent to the suffering of their victim(s). Historically, many scholars have investigated the connection; Murray (2008; Chapter 10) identified nearly 600 correlational and experimental studies directly pertaining to television and film violence over a 50-year period. Although there are some critics who disagree (e.g., Fowles, 1999; Freedman, 1984), most reviews of this research (e.g., Potter, 2008) conclude that violent screen media can increase the likelihood that a viewer or player will think, feel or behave aggressively, as well as experience physiological arousal and exhibit decreased prosocial behavior.

Another negative outcome of media violence exposure – desensitization – is also becoming increasingly prevalent in the literature. Desensitization refers to lowered responsiveness to a negative stimulus (typically screen media) after repeated or prolonged exposure to it, often referred to as habituation (Cline, Croft, & Courrier, 1973). This outcome has been conceptualized as a short-term, immediate reduction in sympathy or concern (Drabman & Thomas, 1974), and as a long-term, cumulative effect caused by repeated exposure to media violence (Thomas, 1982). From what Carnagey, Anderson, and Bushman (2007) call desensitization “processes” (e.g., decreased heart rate) to desensitization “effects” (e.g., empathy for victims of violence), research in this area has not garnered the attention aggression has. However, we argue that desensitization is an equally important outcome to study. In fact, some scholars believe that desensitization may be a far more pervasive effect than aggression; further, as we will address in greater detail, some research suggests that desensitization to media violence can influence reactions to real-world aggression (Thomas, Horton, Lippincott, & Drabman, 1977).

This chapter will focus on the outcomes of aggression and desensitization as they relate to media violence. We will examine the various ways researchers have measured the effects of media violence and structure our chapter by the physiological, cognitive, affective, and behavioral outcomes associated with aggression and desensitization. Next we will address the types of violent media content (i.e., the contextual portrayals) that can heighten the likelihood of desensitization and/or aggressive responses, as well as consider the individual difference variables (e.g., age, gender, etc.) that can increase a person's susceptibility to the effects of media violence. We will conclude this chapter by considering the social significance of aggression and desensitization.

Physiological Outcomes

Researchers have long measured physiological arousal (e.g., heart rate, blood pressure, skin conductance, respiration changes, etc.) during or immediately following exposure to violent or suspenseful media. Investigations of television and film have found that violent messages, as well as sexual depictions, lead to increases in viewers' physiological arousal. Early research by Osborn and Endsley (1971) found that children's galvanic skin response (GSR) levels (i.e., “emotional sweating”) were significantly higher when watching violent cartoons and live-action scenes when compared to nonviolent content. Likewise, Groer and Howell (1990) measured the heart rates and skin temperatures of preschool children while they viewed clips of the nonviolent, slow-paced program, Mister Rogers, and the verbally and physically aggressive, fast-paced program, GI Joe. The researchers found that when compared to watching Mister Rogers, the heart rates of children watching GI Joe were significantly higher.

While the aforementioned studies examined arousal in young children, more recent research has investigated the effects of arousal-inducing television and film content among older audiences. For example, Kalamas and Gruber (1998) examined the electrodural responses of 10- to 15-year-olds exposed to clips of the film, Friday the 13th. The study found a significant increase in participants' physiological reactivity, and responses were stronger during scenes of implied or impending violence (e.g., the perpetrator approaching his victim) when compared to scenes of actual violence (e.g., the perpetrator stabbing his victim). These findings suggest that the suspense leading up to a violent act may be just as arousing, if not more so, than watching a violent act depicted on the screen.

In recent years, researchers have directed their attention to the arousal-inducing effects of violent videogames, with findings largely pointing to an increase in physiological outcomes. For example, Ballard and Wiest (1996) randomly assigned participants to one of three exposure groups: a highly violent version of Mortal Kombat (with blood), a less violent version of Mortal Kombat (without blood), and a nonviolent control game, Corner Pocket. Participants who played either version of Mortal Kombat showed significantly higher cardiovascular reactivity scores (measured by heart rate and systolic blood pressure) than those in the nonviolent condition; further, heart rates and blood pressure scores were significantly higher for those who played the more violent game compared to its less violent counterpart. These findings suggest that videogame violence can increase players' arousal, and that the physiological outcomes can increase with heightened violent content.

In a similar study, Fleming and Rickwood (2001) examined the relationship between violent videogame play and children's physiological outcomes by randomly assigning participants to play a paper-pencil game, a nonviolent videogame, or a violent videogame. Results showed that the children's heart rates and self-reported arousal increased significantly after playing the violent videogame when compared to the other game conditions, with females experiencing greater increases than males.

Despite these findings, some recent research, using the most technologically sophisticated games, suggests that violent content in videogames may be just as arousing as other game elements (e.g., pace, perceptual persuasiveness of graphics, screen size, etc.). For example, Ivory and Kalyanaraman (2007) randomly assigned participants to either a newer or older version of a violent or nonviolent videogame to test players' levels of presence, involvement, physiological arousal, self-reported arousal, and aggression (cognitive and affective). While the technological advancement of newer games increased players' physiological arousal (as measured by skin conductance) and self-reported arousal, there was no support for the researchers' prediction that those in the violent videogame condition would experience greater arousal than those in the nonviolent game condition. Likewise, Barlett, Rodeheffer, Baldassaro, Hinkin, & Harris (2008) failed to find a significant difference in physiological arousal between players of a violent and nonviolent videogame; they attribute this finding to the fact that the games tested in their study were equally exciting. Given these findings, we concur with Ivory and Kalyanaraman (2007) that future research should investigate the effects of content elements (e.g., violence) in concert with other game features (e.g., technological advancement) to better comprehend these variables' relative contributions to physiological arousal and other aggression-related outcomes.

Finally, expanding on the research on physiological outcomes, neuroscientists have charted new territory by studying media violence exposure and brain activation patterns. Using MRI technology, Murray et al. (2006) are investigating children's brain activity while watching violent television (see Chapter 10). At the same time, videogame researchers, such as Weber et al. (2006), have employed similar research designs, with preliminary evidence suggesting that playing violent games is strongly related to brain activity patterns characteristic of aggressive thoughts. While these studies are exploratory and limited by small samples, they provide an innovative foundation from which future neuroscientific research can grow.

Overall, the body of research on screen media suggests that exposure to violent content can lead to subsequent increases in short-term arousal. As noted by Anderson et al. (2003), these findings are especially noteworthy in light of evidence that increased arousal levels can heighten the likelihood of aggressive behavioral responses. In line with excitation transfer theory (Zillmann, 1991), arousal caused by media content (violent or nonviolent) may be misattributed as anger in situations involving provocation and in turn may increase the likelihood of anger-motivated aggressive behavior. In other words, heightened levels of short-term physiological arousal can have subsequent effects on aggression.

While exposure to media violence can indeed increase physiological arousal, researchers have long studied the way in which these responses can subside over time, with individuals' lowered responsiveness to media violence along various physiological measures indicating they are becoming desensitized to media violence after repeated exposure. Researchers have measured differences in physiological responses to exposure to violent media once (Bartholow, Bushman, & Sestir, 2006; Cline et al., 1973) or multiple times (Ballard, Hamby, Panee, & Nivens, 2006). More frequently, researchers exposed subjects to media violence and measured their subsequent physiological responses to a variety of alternate stimuli (Ballard et al., 2006; Linz et al., 1989; Thomas et al., 1977).

In an early study detailing results of two experiments, children who reported being heavy TV viewers had lowered GSR and blood volume pulse amplitude when viewing a violent film (Cline et al., 1973). More recently, adult males who enjoyed and frequently played violent videogames demonstrated different brain activity than men who enjoyed and played them less often (Bartholow et al., 2006). The amplitude of frequent violent game players' P300 event-related brain potential (ERP), which corresponds to aversive reactions to negative (e.g., violent) visual stimuli, was lower than infrequent violent game players' measures, in response to neutral, violent, and negative nonviolent images from Lang, Bradley and Cuthbert's (2001) international affective picture system (IAPS) (Bartholow et al., 2006). Epistemologically, Bartholow et al. (2006) advanced the study of desensitization, in part, by using neutral, violent, and negative nonviolent images from the IAPS in lieu of fictional violence from a Hollywood film. Where Cline et al. (1973) made a theoretical leap from TV exposure to TV violence exposure, Bartholow et al. (2006) had subjects complete a questionnaire regarding favorite videogames and perceived violence within when comprising high- and low-exposure groups. Bartholow et al.'s (2006) primary contribution to desensitization literature was their measurement of a specific brain reaction to stimuli, adding an additional physiological indicator to existing measures. These researchers examined short-term desensitization effects, relying on self-reported prior exposure (assumed or actual) to media violence as an antecedent to physiological responses.

More often, researchers expose subjects to media violence and measure physiological desensitization to subsequent stimuli. Thomas et al. (1977) showed subjects a violent police drama or nonviolent sports film and measured GSR during a subsequent real-world depiction of screen violence; those who previously viewed violence had lower GSR. Males in Linz, Donnerstein, and Adams's (1989) study exposed to “slasher” films had lower heart rates during the final part of violent clips they were exposed to than males who previously viewed nonviolent scenes. Ballard et al. (2006) measured adolescents' heart rate, systolic blood pressure, and diastolic blood pressure while playing violent or nonviolent videogames, and found lowered responses in all three areas not only during game play but across time (from Time 1 to Times 2 and 3); however, the pattern was not exclusive to players in the violent game group. Similarly, male subjects who played a high- or low-violence version of a first-person shooter game for 20 minutes had lower heart and breathing rates over time. In the same study, those who played the high-violence version had lower GSR responses to subsequent exposure to “aversive” IAPS photos (e.g., mutilated corpses) (Staude-Muller, Bliesener, & Luthman, 2008).

Ballard et al. (2006) assessed adolescents' physiological desensitization to violent and nonviolent, active videogames (a) within a 15-minute session and (b) over the course of 3 weekly sessions. Measuring heart rate, systolic blood pressure, and diastolic blood pressure, their results were mixed. Within their gaming session, subjects relaxed, but did not demonstrate steadily decreasing cardiovascular responses. Further, no difference in responses between the violent and nonviolent games was found. Over the course of three weeks, subjects demonstrated decreased physiological responses; again, no differences in responses between violent and nonviolent games were detected. The authors concluded that arousing, but not necessarily violent, games invoked such responses (Ballard et al., 2006).

A crucial aspect of desensitization research is whether the pattern of reduced physiological responses found in most of these studies means individuals will care less or have blunted reactions when exposed to real-world violence. Yet, due to ethical considerations, researchers do not expose participants to actual violence, settling instead for mediated violence presented as real, such as actual news footage or staged conflicts. While operationalization of real- world violence varies, in general, it refers to depictions not created by Hollywood studios for entertainment purposes (Carnagey et al., 2007). Thus, the common trait shared by all content used as real-world examples is that it is mediated. Care should be taken not to mistake desensitization to real-world media violence for desensitization to real-world violence.

Thomas et al. (1977) measured subjects' skin resistance during exposure to real-world violence after viewing violent or nonviolent arousing media. In experiment 1, children watched either an excerpt from a violent television police drama or a volleyball game, followed by a staged violent confrontation between two preschoolers caught on camera. Subjects who watched the violent police drama exhibited lower GSR responses to the real-world violence (i.e., the staged preschooler conflict) than control subjects. Experiment 2 was similar, except for the sample population (college undergraduates) and the real-world violence stimulus (unedited news footage of riots outside the 1968 Democratic National Convention in Chicago). Male subjects followed the predicted pattern (lowered GSR responsiveness); the results were more tentative for females. Carnagey et al. (2007) measured college students' heart rates and GSR before and after playing either violent or nonviolent arousing videogames for 20 minutes. Their physiological responses were measured as they watched a 10-minute videotape of real-world violence (e.g., courtroom outbursts, prison fights). As predicted, subjects who played one of the violent videogames demonstrated lower physiological responses to the violent clips. Recall that high-violence game players in Staude-Muller et al.'s (2008) study had lower GSR responses to aversive IAPS photos; they were also more physiologically sensitive to the aggressive photos, as predicted, which was attributed to a priming effect of the violent videogame.

Thus, in terms of physiological desensitization, questions persist regarding different responses to violent versus active (but not necessarily violent) stimuli, especially as researchers have focused on the effects of violent videogame playing on individuals. Habituation over the course of single and multiple exposures remains a primary emphasis, as does its relationship to subsequent responses to a variety of stimuli, including real-world media examples (themselves often presented in a mediated, though ostensibly non-fictional, context). There is evidence to suggest that violent entertainment media use makes subsequent exposure to violence presented as having actually occurred, less physiologically arousing to research participants.

Cognitive Outcomes

Aggressive cognitions as an outcome of exposure to media violence have been measured in a variety of ways (e.g., word-completion tasks, thought-listing tasks, and word-reaction time tasks), with studies providing evidence of short-term aggressive thoughts following exposure to media violence. For example, Chory-Assad (2004) found that exposure to verbally aggressive TV sitcoms led to an increase in participants' aggressive thoughts. Research on violent movies (Anderson, 1997) and photographs of weapons (Anderson, Benjamin, & Bartholow, 1998) yielded similar results. In the past, researchers of television and film violence (see Chory-Assad, 2004) also applied thought-listing tasks in their research design, and recently videogame scholars have drawn on this measurement tool as well. For example, Tamborini et al. (2004) found that participants who played a violent videogame listed significantly more hostile thoughts than subjects in a nonviolent control group. Anderson and Dill (2000) found that even brief exposure to violent videogames can heighten aggressive thoughts, as measured by a reading-reaction time test. Likewise, Anderson et al. (2004) found that participants who played a violent videogame produced a significantly higher percentage of aggressive words (using a word-completion task) than those in the nonviolent videogame group. However, in a similar study by Cicchirillo and Chory-Assad (2005), aggressive thoughts were not observed among participants who played a violent videogame for 10 minutes. The researchers posit that “perhaps aggressive thoughts are not primed until violent videogames are played for longer periods of time, maybe long enough for players to learn the game and get comfortable playing it” (p. 446). This comfort may in fact be an indicator of desensitization over time.

Measuring cognitive effects in desensitization research often takes the form of perceptions of victims. Linz and colleagues (1989) had subjects view violence against women or arousing, nonviolent content, followed by scenes of men committing acts of violence against women. Participants then assessed perpetrators' and victims' levels of responsibility, levels of violence and victim injury, and victims' attractiveness. Subjects in the violence-viewing group judged the female victims as less injured than did controls; however, they also attributed more responsibility to the perpetrators, a finding the authors described as a possible short-term, sensitizing effect of violence viewing.

Linz, Donnerstein, and Penrod (1984) explored the desensitizing effects of multiple exposures to violent content. On successive days, male subjects viewed “R-rated” violent films containing violence against women in which the female victims are not sexually aroused by the violence and usually end up murdered. On the final day, subjects and members of a control group watched a reenactment of an actual rape trial. Over the course of five days, subjects judged the films as being less degrading to women and less violent. Compared to the control group, subjects also deemed the rape victim in the reenactment as less injured and less worthy of sympathy, leading Linz et al. (1984) to conclude that regular exposure to media violence may reduce sensitivity to victims in other contexts.

Mullin and Linz (1995) explored “spillover” desensitizing effects of sexually violent material, again looking at the impact of viewing slasher films on men's evaluations of domestic violence victims. They sought to determine the persistence of desensitization by having subjects evaluate victims three, five, or seven days after the final exposure. Cognitively, subjects' estimates of the sexual violence in the films decreased over time. Moreover, subjects who evaluated victims three days after seeing the final film perceived less injury than those in the five-day later, seven-day later, and control groups, suggesting a recovered sensitivity on the part of subjects over an extended period of time.

Clearly, evidence suggests that time plays an important role in determining cognitive effects, whether it's during a single exposure to media violence or over the course of multiple exposures to it. The provocation and subsequent subsiding of aggressive thoughts related to media violence exposure suggest a pattern seen less steadily in the realm of affective responses.

Affective Outcomes

Whereas cognitive outcomes involve thoughts and information processing, affective outcomes embody emotions such as fear and anger. Research on television and film has shown that exposure to violence can contribute to feelings of hostility, anxiety, fear, and depression. However, the research on playing violent videogames and aggressive affect is less consistent, with some studies finding a significant relationship (e.g., Ballard & Wiest, 1996; Carnagey & Anderson, 2005; Gentile, Lynch, Linder, & Walsh, 2004) and others showing marginal to no support (e.g., Anderson & Dill, 2000; Scott, 1995).

In a series of experiments, Carnagey and Anderson (2005) explored the effects of rewarded and punished violent acts during videogame play on subsequent aggressive affect, investigating whether aggressive behavior is driven by cognition or affect; i.e., when comparing aggressive thoughts to aggressive affect, which is more likely to influence aggressive behavior? They found that videogame violence, regardless of whether it is rewarded or punished, significantly increased hostile emotions relative to playing a nonviolent game. However, their findings, when compared to their other two experiments testing the outcomes of cognition and behavior, suggest that aggressive cognitions are more likely than aggressive affect to drive aggressive behavior.

While experimental and correlational data provide evidence of a significant link between violent videogame exposure and aggressive affect, other research paints a different picture. Scott's (1995) hypothesis of a linear increase in aggressive affect after playing a non-aggressive computer game (Tetris), a moderately aggressive computer game (Overkill), or a very violent computer game (Fatal Fury), respectively, failed to gain support. Anderson and Dill (2000) found that playing a violent videogame failed to significantly increase state hostility; however, violent videogame play significantly increased aggressive cognitions and aggression behaviors relative to players in the nonviolent game condition. In light of these findings, Anderson and Dill suggest that the effects of violent videogames may take “a cognitive and not an affective path to increasing aggressive behavior in short-term settings” (p. 786), but “do not rule out the possibility that under some circumstances violent videogame effects on subsequent aggressive behavior might be mediated by increased feelings of hostility or by general arousal effects” (p. 788).

Affective and attitudinal desensitization, typically operationalized in the form of sympathy for victims, is a frequent research focus. Recall the work of Linz et al. (1989), who took measurements of the moods (hostility, anxiety, and depression) of males who viewed violence, immediately after viewing and again after seeing the dependent measure clips. They found that exposure to violence had a short-term desensitizing effect on mood. Controls experienced increases in the three mood measures after viewing the violent clips, whereas experimental subjects did not (Linz et al., 1989).

In 1988, Linz, Donnerstein, and Penrod had male subjects watch either two or five slasher, “X-rated,” or less explicit teen sex films, then view and evaluate a reenactment of either an acquaintance or nonacquaintance rape trial. Linz et al. (1988) predicted lowered responsiveness from subjects who viewed the sexual violence in the slasher films than those who saw nonviolent, sexual content, as well as differences in responses to the reenactments. Over time, sexually violent material that initially provoked negative affective responses (e.g., anxiety) in subjects subsided. Violence-viewing subjects were less sympathetic to the rape victim in the trial, and less able to empathize with rape victims in general than other subjects and controls. However, longer exposure periods were needed to affect the latter response. In subsequent work exploring the effects of multiple exposures to violence over time, subjects in Mullin and Linz's (1995) study became desensitized by viewing three slasher films in five days, displaying decreased hostility, but not anxiety or depression.

More recently, Fanti, Vanman, Henrich, and Avraamides (2009) examined short-term desensitization effects by showing subjects nine violent and nine comic scenes (alternating) and having subjects assess enjoyment of all eighteen and sympathy toward victims in the nine violent clips. Using latent growth-curve modeling, Fanti et al. (2009) discovered divergent curvilinear paths for enjoyment and perceived victim sympathy during violent scene viewing. Over the course of multiple exposures to violence in the short-term, subjects' enjoyment started at a midpoint on the researchers' scale, decreased at first, and at clip five began a steady escalation culminating in highest levels of enjoyment for the ninth violent clip. Victim sympathy also began at a midpoint on the researchers' scale, increased at first, and at clip five began a steady decline paralleling the increases in perceived enjoyment. Fanti et al.'s (2009) work suggests that short-term desensitization effects are not always linear, as has been found in the past, but also can be curvilinear. The pattern of increased sympathy and decreased enjoyment evident by the midway point of their experiment provides some evidence for the possibility of short-term sensitization that may coexist with more conventional desensitization findings.

Funk, Bechtoldt Baldacci, Pasold, and Baumgartner (2004) assessed long-term desensitization effects of media violence on children through survey methodology. They assessed relationships between real-life and media violence exposure and desensitization, predicting lower empathy and stronger proviolence attitudes among children who report greater exposure levels, especially regarding videogame violence. Exposure to videogame violence was associated with lower empathy and stronger proviolence attitudes. Movie violence exposure was also associated with stronger proviolence attitudes. However, real-life violence exposure did not correlate significantly with either measure. Yet, their correlational survey data do not rule out the possibility that individuals with more proviolent attitudes and less empathy seek out more violent media rather than the violent media necessarily causing the proviolent attitudes or lack of empathy.

Funk, Buchman, Jenks, and Bechtoldt (2003) examined short- and long-term desensitization effects, focusing on relationships between children's exposure to videogame violence and their empathy, game preference, and attitudes toward violence (components of moral evaluation). To assess short-term effects, Funk et al. (2003) examined children's empathic responses to vignettes after playing a violent or nonviolent videogame and responses to vignettes in which they were asked what would happen next in the scenario, what they would do, and so on. To assess long-term effects, they explored relationships between exposure, preexisting empathy and attitudes toward violence, and vignette responses. No significant effect of type of game played on short-term empathic responses was found. However, participants with greater long-term exposure to violent videogames displayed lower preexisting empathy and lower scores on empathy vignettes. Thus, long-term exposure to violent videogames appears to have desensitized child participants, at least in terms of their levels of empathy, whereas short-term effects of playing a violent videogame (versus playing a nonviolent one) did not, suggesting a coarsening over time in the violent videogame player not paralleled in a single session.

Finally, Scharrer (2008) turned the lens to news content by exploring the relationship between amount of exposure to television violence, local newspapers, and local television news and responses to news stories chronicling violent events (dependent measure). By focusing on emotional responses to the dependent news stories, perception of violence in them, and perception of the events covered as commonplace, the relationship between trait empathy – a frequent desensitization indicator (though not here) – and desensitization was explored. Respondents who reported higher exposure to violent entertainment television, local newspapers, and local television news were less sensitive to the violent news stories. Other predicted desensitization effects provided less uniform results. Trait empathy, as operationalized in this study, interacted with some forms of media exposure to predict emotional responses to and perceptions of the dependent measure stories, leading Scharrer (2008) to conclude that trait empathy plays a role in identifying individuals most susceptible to desensitization.

Along with the physiological indicators discussed previously, examination of cognitive, affective, and attitudinal responses provides a complete picture of the study of desensitization, with time playing a significant role in the process. The common focus on relationships between desensitization and subsequent exposure to stimuli will most likely continue to shape future inquiry, as will connections to aggression.

Behavioral Outcomes

Research has long shown that exposure to media violence can increase the likelihood of aggressive behavior and decrease the likelihood of prosocial behavior. Given that this volume includes a chapter on prosocial behavior (see Mares, Chapter 30), we will only address the research pertaining to aggressive behavior. Aggressive behavior, especially in correlational research, has been assessed using a variety of measures including self-reported, peer-reported, parent-reported, and teacher-reported aggression. Likewise, experimental studies have measured aggression in several ways, including observing participants in free-play situations, measuring the duration of noxious blasts that participants deliver to “opponents,” and employing projective tests.

Lab experiments dating back to the 1960s (e.g., Bandura, Ross, & Ross, 1963) demonstrate that television and film violence can cause short-term behavioral effects in some children and adolescents. Reflecting on the body of research, Sparks and Sparks (2002) contend that experimental data is “so consistent in favor of the conclusion that exposure causes increased aggression that fewer experiments have been conducted in recent years” (p. 275). Yet, there are some noteworthy examples of contemporary research. For example, Scharrer's (2005) study, which examined the moderating role of personality, found some evidence that violent television programs can elicit a stronger effect among males with a higher level of trait aggression than their less aggressive counterparts.

To address limitations typically associated with lab-based research (e.g., artificiality, questionable measurement techniques, and the inability to assess long-term effects), scholars have conducted notable field experiments, including Boyatzis, Matillo, and Newbitt (1995), who found that exposure to Mighty Morphin Power Rangers led to a significant increase in children's physical and verbal aggression in the classroom. In addition, longitudinal studies (see Huesmann & Eron, 1986; Huesmann, Moise-Titus, Podolski, & Eron, 2003) provide convincing evidence that long-term exposure to television violence during childhood predicts aggression and, in some cases, criminal behavior, in adulthood. Despite the limitations of laboratory research, it is important to highlight the work of Anderson, Lindsay, and Bushman (1999), who found that the cumulative effect sizes of lab- and field-based studies are quite similar, thereby suggesting that laboratory research is externally valid.

Collectively, whereas the body of research on television and film violence is large and fairly consistent, the literature on violent videogames and their behavioral effects is smaller in size and occasionally yields some conflicting results. Gentile et al.'s (2004) survey of middle school students found that time spent with violent videogames was a significant predictor of both self-reported arguments with teachers and self-reported physical fights with peers. Likewise, Bartholow, Sestir, and Davis' (2005) survey of college-aged males found that exposure to violent videogames is significantly correlated with self-reports of aggressive behavior. However, Wiegman and van Schie's (1998) survey of Netherlands youth failed to show a relationship between overall exposure to videogames and peer-reported aggression.

In addition to surveys, experimental research has found that undergraduates who played violent videogames punished confederates by delivering stronger blasts of noxious noise than did participants who played a nonviolent videogame (Anderson et al., 2004; Bartholow & Anderson, 2002). More recently, in exploring the role of game attributes, Fischer, Kastenmuller, and Greitemeyer (2010) found that college subjects who played a violent videogame using a personalized character exhibited more aggressive behavior (measured by participants' willingness to dispense hot chili sauce to a subsequent participant) than those who played a violent videogame using a nonpersonalized character. Other research, such as Williams and Skoric's (2005) longitudinal study of an online violent videogame, failed to show an increase in behavioral aggression, whereas Anderson et al. (2008) found a significant, positive longitudinal relationship between playing violent videogames and aggressive behavior. Despite some inconsistencies in the research findings, it is important to note that three meta-analyses (Anderson, 2004; Anderson & Bushman, 2001; Sherry, 2001) have found that, in the aggregate, there is a positive and significant relationship between videogame violence exposure and subsequent aggressive behavior.

The possibility that becoming desensitized to violence leads the way toward aggressive or even violent behavior is a matter of strong social significance. If individuals who see a great deal of violence in the media consider violence to be nonarousing, normative, and no real cause for concern, might this disinhibit their own aggressive tendencies? For instance, research into the relationship between videogame violence exposure and aggression has explored the potential mediating role desensitization can play, leading some to speculate that physiological desensitization (e.g., reduced heart rate) or desensitization effects (i.e., empathy) could play a mediating role between exposure and aggression (Carnagey et al., 2007). Based on subjects' physiological responses to pictures from the IAPS following game play, Staude-Muller et al. (2008) found that players in a high violence game-playing group were more sensitive to aggressive cues than subjects who played a low-violence version of the same first-person shooter, a difference “explained by the priming of aggressive knowledge structures . . . pre-activated by the aggressive content . . . and more easily accessible [by subjects in the high-violence group]” (p. 48). Bartholow et al. (2005) examined the role of empathy as a mediator of the effect of videogame violence exposure on aggression. In their primary analysis, empathy was not a significant mediator of aggression. Despite finding a significant mediating role between exposure and a specific aspect of laboratory aggression, Bartholow et al. (2005) concluded that empathy appears to play a weaker mediating role than hostility, for which the team also tested. While there is not yet convincing evidence supporting a mediating role for desensitization between exposure and aggression, researchers continue to study the connections between these two areas of effects to better understand their relationship to one another.

Violent Content in Context

Research, in particular the National Television Violence Study (NTVS, Smith et al., 1998; Wilson et al., 1997, 1998), has identified “high-risk” contextual features of mediated violence that facilitate or inhibit aggressive thoughts, attitudes, and/or behaviors. For example, drawing on social cognitive theory, research shows that rewarded violence or violence that goes unpunished increases the likelihood of learning aggression, whereas punished aggression diminishes the risk. Likewise, aggression committed by an attractive perpetrator has been shown to increase the likelihood of learning from mediated aggression, whereas violence committed by unattractive or unlikable characters reduces this risk. Along these same lines, the more a person identifies with perpetrators of media violence (especially those perceived as attractive or likable), the more likely he or she will learn from the character's actions. Studies have also found that justified violence (e.g., using violence to “save the day”) enhances the likelihood of an aggressive outcome; unjustified violence decreases this likelihood. Finally, we know that the presence of weapons, especially conventional ones (e.g., guns, knives), violence that appears “realistic,” and humorous violence can promote the learning of aggression.

Potter (2008) presents a provocative point about violent media and desensitization in Media Literacy:

Based on his work analyzing television violence (Potter & Smith, 2000; Wilson, Smith, Potter et al., 2002), he contends that humorless, highly graphic violence offends people, leading them to call for its strict control or elimination from media content. Potter (2008) views this as an inappropriate action based on an appropriate response; that is, being offended by media violence is an indication of sensitization to it, which is a reasonable, if not healthy, response. If media outlets simply make violence more humorous or portray its consequences as less serious, it may placate the offended, but they (the media outlets) are only sanitizing the content, and essentially desensitizing the audience to it.

Consider the violence in the “R-rated” Saving Private Ryan (highly graphic and sensitizing) compared to the violence in most “PG-13-rated,” comic book-inspired films (less graphic and desensitizing). Where the violent depictions in the restricted (by MPAA rating) Spielberg film could sensitize viewers to the horrors of war and human suffering, those in unrestricted superhero franchise films could have the opposite effect, highlighting the violent exploits of a heroic character while trivializing the suffering of victims. Or think about the violence found on television, where “programs targeted to children . . . contain more violence overall and . . . it is far more likely to be sanitized and trivialized [than violence in nonchildren's shows]” (Wilson et al., 2002, p. 29). When Leone and Barowski (2011) examined “ratings creep” (the notion that, over time, adult content escalates in films with the same rating), they found that violence in PG-13-rated films increased significantly since 1988. Of the over 2,000 violent sequences coded, from mild (1) to rough and persistent (5), the majority (nearly two-thirds) were mild; this is precisely the kind of desensitizing violence to which Wilson et al. (2002) and Potter (2008) refer. Leone and Barowski's findings coincide with Carnagey et al.'s (2007) conclusion that “the modern entertainment media landscape could accurately be described as an effective systematic violence desensitization tool” (p. 495), and the violence found in PG-13 films would be a major structure in that landscape.

Who is Most Susceptible?

While all media consumers are potentially vulnerable to media violence, research has indicated that some people are more susceptible than others. Over the years, researchers have identified several factors (often referred to as “individual differences”) that heighten a person's susceptibility to the effects of media violence. For example, critics concerned with media violence have positioned young children as a unique audience especially susceptible. This concern is indeed warranted, with Paik and Comstock's (1994) meta-analysis finding an inverse relationship between the age of the viewer and the magnitude of the effect of television violence on aggression. In addition to age, gender is another individual difference variable of interest to researchers. Paik and Comstock's analysis revealed that television violence tends to have a stronger effect on males than females, in part because males often pay more attention to violence. However, in recent years, research suggests that females are increasingly susceptible to media violence; this is partly attributed to societal change, the increase in aggressive female media characters (Jansz & Martis, 2007), and the increase in females playing videogames (Entertainment Software Association, 2010). Clearly, more research is needed to shed greater light on gender and susceptibility to media violence.

In addition to age and gender, researchers have studied the role of personality traits – especially trait aggression – in the relationship between media violence exposure and aggressive outcomes (see Chapter 8). Slater, Henry, Swain, and Anderson's (2003) “downward spiral model” is especially relevant to this area of research. Their model suggests that youth with a high level of trait aggression seek out violent media content and that exposure to media violence predicts aggressive outcomes in youth, such that both relationships are mutually reinforcing. Indeed, some research has found that characteristically aggressive young people are more likely to be influenced in the short-term by viewing media violence than those without aggressive traits (Anderson & Dill, 2000, Study 1; Scharrer, 2005).

Playing videogames complicates the relationship between individuals' trait aggression and the effects of media violence in ways viewing it on television or film do not. The player's ability to modify game content is one of the key characteristics of “interactivity” distinguishing gaming from traditional media viewing. Further, players' individual differences variables (e.g., age, gender, personality traits, etc.) are likely to shape how they play and respond to the game. In short, since a player controls his or her character's actions, we must consider that there are certain types of people with preexisting personality traits, such as trait aggression, who may play violent videogames using a more aggressive playing style; furthermore, an aggressive in-game playing style may shape post-playing aggressive outcomes. Cicchirillo and Chory-Assad (2005) emphasize that very little research has taken into account the extent to which players' personality traits may moderate negative outcomes; they go on to issue a call for research whereby “researchers should consider capturing the game play of their participants (e.g., recording it on DVD or videotape) and comparing the actual content played or produced by the game players to their aggressive responses” (p. 447).

Paradise (2007) responded to this call by conducting an exploratory study to test whether trait aggressiveness shaped aggressive in-game playing choices, and consequently whether aggressive playing choices influenced players' short-term aggressive thoughts. As hypothesized, results indicated that participants who played a violent videogame (24: The Game) produced more aggressive thoughts than those who played a nonviolent game (Tetris); however, contrary to the hypothesis, trait aggression did not moderate this relationship.

Data obtained by measuring participants' in-game playing style of 24: The Game also revealed that individuals play violent videogames in vastly different ways, with players' in-game violent acts varying substantially (between 57 to 255 acts). Subsequent analyses indicated that participants' trait aggressiveness did not influence their style of videogame play (more aggressive versus less aggressive). However, results showed that a more aggressive playing style predicted aggressive thoughts. It is important to note that, to our knowledge, only one other study (see Peng, Liu, & Mou, 2008) has examined the relationship between trait aggression and playing style, finding that those with high-trait aggression employed a more aggressive style of game play, even after controlling for prior gaming experience and gender. Given that Peng and colleagues' (2008) findings are contrary to those found in Paradise's (2007) experiment, more research is needed to examine this relationship.

Conclusion

The connections between exposure to media violence, aggression, and desensitization extend across various effects dimensions, from physiological and cognitive to affective and behavioral. And the evidence chronicling myriad effects of screen media violence on people, from young children and preadolescents to teens and adults, is supported by decades of research examining these phenomena. If one factor stands out as guiding the thinking about, research into, and future examination of these connections, it is time. As we gain insight into the importance of time, the complex relationship between these factors will be further explained.

What we do know is that the relationship between exposure to media violence, aggression, and desensitization is not necessarily linear. In the short-term, exposure can lead, initially, to increased responsiveness suggesting aggressive effects. However, at certain time thresholds, there is evidence of decreased responses, thus suggesting a desensitization effect. It seems clear that this pattern of increased responses that give way to decreased ones guides much of the research in the field, and will continue to do so in the future.

When considering these effects in the long-term, an even more complex relationship may emerge. Over time and multiple exposures to media violence, people become desensitized not only to the violent content itself but to a host of other stimuli. Just how long this desensitized condition lasts is still uncertain, as is its role in facilitating aggressive behavior, but scholars will continue to examine the relationship between these two areas of media effects. Likewise, future researchers must address the important contextual factors of violent content, especially with the increasing sophistication and vividness of videogames. How violence is portrayed (or perpetrated) on screen, and its influence on the people who are exposed to it most, must guide future research.

Ultimately, we return to central questions of media effects: Are people with trait aggression drawn to violent media, and, if so, does further consumption of it numb them to its effects, and by extension to the world and people around them? Subsequently, does it make those people more aggressive? The evidence suggests that the answer to most of these questions is a qualified “yes.” Aggressive people consume a lot of violent media, and, over time, are less reactive to it both short- and long-term, which carries over into other areas of their lives. How far and for how long it carries over will shape these lines of inquiry in the future.

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