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This article was submitted to Psychopathology, a section of the journal Frontiers in Psychology
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The use of violent video games has been often linked to increase of aggressive behavior. According to the General Aggression Model, one of the central mechanisms for this aggressiveness inducing impact is an emotional desensitization process resulting from long lasting repeated violent game playing. This desensitization should evidence itself in a lack of empathy. Recent research has focused primarily on acute, short term impact of violent media use but only little is known about long term effects. In this study 15 excessive users of violent games and control subjects matched for age and education viewed pictures depicting emotional and neutral situations with and without social interaction while fMRI activations were obtained. While the typical pattern of activations for empathy and theory of mind networks was seen, both groups showed no differences in brain responses. We interpret our results as evidence against the desensitization hypothesis and suggest that the impact of violent media on emotional processing may be rather acute and short-lived.
The possible influence of violent video games (VVG) on human aggressive behaviour is hotly debated. According to research done in the context of the General Aggression Model (GAM) a direct and causal relationship between the use of VVG and aggressiveness (
The alternative Catalyst Model postulates only little or no effects of VVG use on human aggressive behavior (
The literature regarding short term desensitization effects of VVG has been inconsistent. Some short term desensitization effects could be shown regarding physiological reactivity, i.e., reduction in heart rate or galvanic skin reactions to violent stimuli (
As
All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the ethic committee of the Medical School Hannover. All participants were also provided with short briefing prior to the experiment. First possible contradictions for MRI measurements were cleared by standard questionnaire and then all necessary information regarding the study was given (e.g., experimental task). The subjects had also the possibility to ask questions before the experiment. After the experiment all subjects were provided with standard debriefing containing additional information regarding the study.
As use of VVG and aggressive behavior is more prevalent in men, only male participants were recruited. Inclusion criterion for the VVG user group was consumption of violent games of the first-person shooter category (e.g., Counterstrike, Call of Duty or Battlefield) for at least 4 years and for at least 2 h daily. First-person shooter games are centered on combat situations seen from the first-person perspective, involving virtual weapons (mostly automatic rifles). Control subjects did not have any experience with VVG (self-report). We also excluded all control subjects that reported a daily use of any video games. All participants were free of psychiatric and neurological disorders as assessed clinically by the senior author, a board-certified psychiatrist. One participant of the VVG group was excluded from the analysis due to taking antidepressant medication. All of the subjects had normal or corrected to normal vision. Experimental and control groups were matched for school education and age.
For the experiment 15 VVG users (mean age 22.8 ± 4.3 years) and 15 control subjects (mean age 22.1 ± 3.0 years) were recruited (difference n.s.). The VVG users had played violent games since 13.1 ± 4.4 years for about 4.0 ± 1.3 h daily.
To avoid possible immediate effects of violent games all participants refrained from playing for at least 3 h prior to the experiment during which time they were informed about the experiment and were prepared for data acquisition. The actual time without playing VVG before the experiment was considerably longer in most subjects.
The experimental stimulation in this study is based on a previous publication and uses black- line drawings on a gray background (
The stimuli were presented for 4 s in pseudorandom order each with varying interstimulus interval (ISI). For each of the four experimental categories 24 different stimuli were used. Between the stimuli a black central fixation cross was presented on gray background. ISI varied pseudo-randomly within each category with 15 intervals of 6 s duration, 5 intervals of 8 s duration and 2 intervals each of 10 s and 12 s duration. During fMRI scanning participants were instructed to watch the pictures carefully and imagine how they would feel in the depicted situation. Presentation software (Neurobehavioral Systems, Inc.) was used to deliver stimuli. Stimuli were presented via an MRI-compatible video display mounted into prepared glasses (CinemaVision, Resonance Technology Inc., USA). Prior to fMRI scanning a test picture was presented to ensure good visibility of stimuli for each participant.
Magnetic-resonance images were acquired on a 3-T Siemens Magnetom Scanner (Erlangen, Germany) equipped with a standard head coil. A total of 545 T2∗-weighted volumes of the whole brain (EPI-sequence; TR 2000 ms, TE 30 ms, flip angle 80∘, FOV 192 mm, matrix 642, 34 slices, slice thickness 3 mm, interslice gap 0.75 mm) near to standard bicommisural (AC-PC) orientation were collected. After the functional measurement a 3D high resolution T1-weighted volume for anatomical information (MPRAGE-sequence; matrix 192 × 2562, 1 mm isovoxel) was recorded. The subject’s head was fixed during the entire measurement to avoid head movements.
Prior to fMRI scanning data from different psychological questionnaires was collected. We used the German adaptation (“Der Saarbrücker Persönlichkeitsfragebogen zur Messung von Empathie”) of the Interpersonal Reactivity Index (IRI) with its four subscales: PT- perspective-taking, FS- fantasy scale, EC- empathic concern, and PD- personal distress (
Analysis and visualization of the data were performed using Brain Voyager QX (Brain Innovation BV, Maastricht, The Netherlands) software (
For the statistical model a design matrix including all conditions of interest was specified using a hemodynamic response function. This function was created by convolving the rectangle function with the model of
Main effects of all factors and their interaction were considered. The false discovery rate threshold of q(FDR) < 0.01 (
Group differences were obtained only for the factor Novelty Seeking of the Temperament and Character Inventory [
The analysis of fMRI data revealed at q(FDR) < 0.01 strong effects for the main factor emotional content (
Brain areas identified for the ANOVA.
Brain structure | Hemisphere | Talairach center of mass | Cluster size (mm3) | ||
---|---|---|---|---|---|
R | 44 | 26 | 3 | 1242 | |
R | 41 | 10 | 28 | 1458 | |
Superior Temporal Gyrus, BA39 | R | 50 | -52 | 14 | 4401 |
R | 6 | -75 | 3 | 648 | |
Medial Frontal Gyrus, BA9 | L | -1 | 47 | 30 | 918 |
L | -42 | 18 | 8 | 3645 | |
Middle Frontal Gyrus, BA6 | L | -39 | -2 | 44 | 945 |
L | -48 | -57 | 9 | 9180 | |
R | 58 | -19 | 33 | 837 | |
R | 48 | -53 | 16 | 6480 | |
Cuneus, BA18 | R/L | 1 | -72 | 18 | 34911 |
L | -48 | -59 | 17 | 6750 | |
R | 24 | -38 | -10 | 3294 | |
L | -28 | -44 | -10 | 3861 | |
Middle Temporal Gyrus, BA19 | L | -34 | -78 | 26 | 540 |
A central claim of the GAM regarding the effects of VVG is desensitization toward emotional stimuli. Although some evidence has been provided for short term effects of VVG in the sense of a decreased empathy and increased of aggressiveness (
Thus, the lack of group differences in our fMRI data dues not suggests, that excessive VVG use leads to long term emotional desensitization and a blunting of neural responses related to empathy. This is corroborated by the questionnaire data which did not reveal differences between VVG users and controls for empathy and aggression measures, even though some differences emerged for measures assessing novelty seeking and antisocial personality.
Most previous studies have focused on immediate effects of VVG use (
The missing group effect in our fMRI data is not really surprising giving the fact that both groups showed also no differences in empathy and aggressiveness as assessed by psychological tests. Our data therefore is in line with the Catalyst Model of violent media influence on individual behavior which posits that these do not increase aggressive behavior but may influence the way how aggressive behavior is displayed. Therefore, aggressiveness itself results more from other aspects than violent media use. This idea is supported by our data. VVG users differ in personality trait Novelty Seeking. As Novelty Seeking is highly correlated with Sensation Seeking (
Before concluding our results we want to put some attention to the limitations of the study. Thus we did not found group differences in our fMRI data set. Null findings in imaging studies are notoriously problematic (
To summarize, our results provide additional evidence against the desensitization hypothesis of VVG use and human aggression. Research on media impact on aggressive behavior should focus on short term (influencing the subject’s state) as well as long term impact (possibly influencing trait aggressiveness). Moreover, additional paradigms should be employed, e.g., facial expression tasks (
GS designed the study, collected and analyzed the data, interpreted the results and wrote the manuscript. BM collected the data and supported the interpretation of the results. TM supported the interpretation of the data and wrote the manuscript. BtW designed the study, collected the data and supported the interpretation of the results.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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