Chronic violent video game exposure and desensitization to violence: Behavioral and event-related brain potential data

Abstract

Numerous studies have shown that exposure to media violence increases aggression, though the mechanisms of this effect have remained elusive. One theory posits that repeated exposure to media violence desensitizes viewers to real world violence, increasing aggression by blunting aversive reactions to violence and removing normal inhibitions against aggression. Theoretically, violence desensitization should be reflected in the amplitude of the P300 component of the event-related brain potential (ERP), which has been associated with activation of the aversive motivational system. In the current study, violent images elicited reduced P300 amplitudes among violent, as compared to nonviolent video game players. Additionally, this reduced brain response predicted increased aggressive behavior in a later task. Moreover, these effects held after controlling for individual differences in trait aggressiveness. These data are the first to link media violence exposure and aggressive behavior to brain processes hypothetically associated with desensitization.

Introduction

Most people naturally have aversive reactions to the sight of blood and gore. Some people (e.g., soldiers, surgeons) must overcome these reactions in order to effectively perform their duties. This example illustrates the process of desensitization, defined as diminished psychological or emotional responsiveness to a stimulus after repeated exposure to it (see Wolpe, 1982). Desensitization can be adaptive because it enables people to ignore irrelevant information and focus instead on relevant information. For most people, however, becoming desensitized to blood and gore can have deleterious social consequences, such as reducing inhibitions against behaving aggressively.

Hundreds of studies have shown that exposure to media violence increases aggression (see Anderson and Bushman, 2001, Anderson et al., 2003). Media violence is believed to increase aggression, at least in part, by desensitizing viewers to the effects of real violence (e.g., Griffiths and Shuckford, 1989, Smith and Donnerstein, 1998). Media violence initially produces fear, disgust, and other avoidance-related motivational states (Cantor, 1998). Repeated exposure to media violence, however, reduces its psychological impact and eventually produces aggressive approach-related motivational states (Cline et al., 1973, Linz et al., 1989), theoretically leading to stable increases in aggression.

Extant research on media violence desensitization has been limited in a number of respects. For example, although desensitization is believed to have both cognitive and emotional components (see Funk, Bechtoldt-Baldacci, Pasold, & Baumgartner, 2004), most research has focused only on the emotional component (see Smith & Donnerstein, 1998). Additionally, very few studies to date have examined how repeated exposure to media violence affects brain processes (but see Kronenberger et al., 2005), and no studies have examined potential links between physiological indices of desensitization and aggressive behavior. Strong support for the desensitization account of media violence effects will be indicated only if processes associated with desensitization can be linked to increases in aggressive behavior.

Theoretically, desensitization should be reflected in the amplitude of the P300 component of the event-related brain potential (ERP). ERPs are voltage deflections in the electroencephalogram (EEG) that reflect the engagement of various information processing activities in the brain (see Fabiani, Gratton, & Coles, 2000). The amplitude of the P300 component of the ERP, often associated with working memory updating (Donchin & Coles, 1988), also has been shown to reflect the extent of evaluative categorization during processing of affective or emotionally relevant stimuli (e.g., Cacioppo et al., 1993, Ito et al., 1998b). Large P300 amplitudes are elicited over midline parietal scalp regions by stimuli that are evaluatively inconsistent with a preceding context (Bartholow et al., 2001, Cacioppo et al., 1993, Ito et al., 1998b). For example, infrequent negative target images presented in a context of frequently presented neutral images elicit large P300s (Ito et al., 1998b). It follows, then, that violent images presented in a context of neutral images should also elicit large P300s. To the extent that an individual is desensitized to violence, however, the P300 elicited by violent images should be reduced. Moreover, to the extent that a P300 reduction reflects motivational processes associated with desensitization to violence, the P300 reduction should be restricted to evaluative categorization of violent images and not to negative images more generally.

Furthermore, if desensitization helps to explain the link between media violence and aggression, and if electrocortical responses to violent stimuli reflect desensitization, then decreases in P300 amplitude to violent images should be associated with increases in aggression. A number of studies have shown that the P300 elicited by negative information reflects activation of the aversive/withdrawal motivational system (e.g., Cacioppo et al., 1994, Ito et al., 1998b). Given that aggression is incompatible with withdrawal motivation (see Harmon-Jones, 2003), and that desensitization theoretically weakens the aversive motivation system pertaining to violence (Cantor, 1998, Funk et al., 2004), there should be an inverse relationship between P300 amplitudes elicited by violent stimuli and indices of aggressive behavior.

Critics of the link between media violence and increased aggression often claim that media violence exposure effects are spurious, masking the effect of some unmeasured third variable such as aggressive personality (Freedman, 2002). In other words, aggressive individuals are simply drawn to violent media. If this hypothesis is correct, controlling for individual differences in aggressive disposition should eliminate or significantly reduce the effects of exposure to media violence on relevant outcomes. Critics also argue that laboratory experiments showing increased aggression following violent media exposure simply reflect a priming effect, likely lasting only a few minutes, which does not carry over into the “real world” (e.g., Fowles, 1999, Freedman, 1984). The desensitization account is at odds with both of these alternative interpretations, predicting that media violence exposure leads people to aggress (not that aggressive people seek out violent media) and that repeated exposure has lasting deleterious consequences. The current study tests these competing interpretations.

In this study, violent and nonviolent video game players completed a visual oddball task in which neutral, violent, and negative nonviolent target images were presented in a neutral image context while ERPs were recorded. Later, participants engaged in a competitive task during which they could blast another “participant” with loud noise; this task was used to measure aggression. We predicted that violent video game players would show deficits in P300 amplitude to violent images, but not to negative nonviolent images, relative to nonviolent game players. We further predicted that violent game players would behave more aggressively in the competitive task, and that P300 amplitudes to violent (but not nonviolent) images would be inversely related to aggressive behavior. Finally, we predicted that these effects would remain when individual differences in aggressiveness were statistically controlled.