Effect of Exposure to Gun Violence in Video Games on Children's Interest in Real Guns: A Randomized Clinical Trial
Phase: NA
Conditions: Psychology, Social, Adolescent Behavior
Sponsor: Ohio State University

Effect of Exposure to Gun Violence in Video Games on Children’s 
Dangerous Behavior With Real Guns: A Randomized Clinical Trial 
NCT03259139 
Last Updated: 4/5/19 

 Protocol and Statistical Analysis Plan 
 
Study Protocol 
 
Objectives 
This research tests the effects of the mere presence of guns in the mass media (e.g. movies, video games, TV 
programs) on children. We predict that seeing guns in the mass media will increase subsequent aggression, 
and will lead to more positive attitudes about guns. 
 
Background and Rationale 
On 14 December 2012, after shooting his mother, 20-year-old Adam Lanza shot and killed 20 children and 6 
employees in Sandy Hook elementary school, in Newtown, Connecticut. In the wake of the Newton 
shootings, there has been considerable discussion about gun violence. What is conspicuously absent from 
these discussions, however, is the fact that just SEEING guns can increase aggression.i This effect, called the 
“weapons effect,” has been replicated in over 50 other studies.ii The effect occurs for angry and non-angry 
individuals, both inside and outside the lab. 
 
A recent analysis of top selling films found that the depiction of guns in violent scenes in PG-13 films that 
target youth has increased from the level of G and PG files in 1985 when the rating was introduced, to the 
level of R films by 2005, to exceed the level of R films since 2012.iii By definition, a PG-13 movie is supposed 
to have less violence than an R-rated movie. The Motion Picture Association of America says on its website 
that the violence in a PG-13 movie “does not reach the restricted R category.” Our study shows that it does. 
By including guns in violent scenes, film producers may be inadvertently increasing aggression in youth via a 
weapons effect. Experiment 1 directly tests this hypothesis. Previous research has shown that when exposed 
to movie characters that smoke, many youth are more likely to start smoking themselvesiv; the same is true 
for characters that drinkv. Similarly, we predict that youth will be more interested in acquiring and using 
guns after exposure to gun violence in films. We also predict they will behave more aggressively following 
exposure to guns in movies. 
 
Experiment 
Participants will be children 8-12 years old. Children will be tested in pairs. Each child will bring a sibling, 
relative, or friend to the study. Participants and partners will each receive a $25 gift card. The design is a 
2 (watch vs. play) by 3 (non-violent, violent with swords, violent with guns) between-subjects design. 
The outcome variables are the time spent handing a gun (in seconds), the number of times the trigger is 
pulled, and the number of times the trigger is pulled while pointing the handgun at oneself or another. 
After filling out a pre-test survey measuring trait aggression and media diet, one participant will be 
randomly assigned to play a video game while the other watches. The video game participants will play 
is a modified version of Minecraft. The participant pairs will be randomly assigned to one of three 
conditions: a non-violent condition with no weapons and no monsters, a violent condition with swords 
and monsters, and a violent condition with guns and monsters. Participants will play for 20 minutes, 
after which they will fill out a survey measuring their familiarity with Minecraft and their opinion toward 
the game. 
 
After completing the survey, participants will be placed in a room containing games and toys, with 
hidden cameras. Participants will be told that they can play with any of the games and toys in the room 

for the next 20 minutes. The toys and games will be in two drawers of a cabinet, while the bottommost 
drawer will contain two Sig Sauer P250 handguns. The handguns have been disabled and are unable to 
fire. In addition, a counter is placed inside the magazine well to count the number of times the trigger is 
depressed with enough force to discharge the handgun. This allows us to distinguish reliably the children 
who pull the trigger from those who handle the gun but do not pull the trigger. Parents will be asked to 
predict whether their child will handle the real gun and pull the trigger. The researcher and the parents 
will be able to watch the session via a monitor in a control room. After 20 minutes, the participants will 
fill out a survey on their attitudes toward guns. A thorough debriefing will follow. 
 
We predict that participants who play the game with guns will handle the gun longer, pull the trigger 
more times, and point the gun at oneself or another and pull the trigger more times than participants in 
the other conditions. One week after a child participates in Experiment 3, the researcher will call or 
email the parent to follow up. 
Attitudes Toward Guns 
To measure participants’ attitudes toward guns, we will use the 15-item Attitudes Towards Guns and 
Violence Questionnaire (see Appendix C)vi, which has been validated on children 6-17 years old and 
young adults.vii It contains three subscales: Comfort With Aggression (e.g., “I don’t like being around 
people with guns because someone could end up getting hurt” and “I wish everyone would get rid of all 
their guns”), Excitement (e.g., “I bet it would feel really cool to walk down the street with a gun in my 
pocket” and “I think it would be fun to play around with a real gun”), and Power/Safety (e.g., “Carrying a 
gun makes people feel powerful and strong” and “Carrying a gun makes people feel safe”). Items are 
scored using a 5-point scale (1=Strongly disagree to 5=Strongly agree). We will also measure whether 
the child has ever fired a gun, and whether the child has taken a gun safety class. 
 
Prior to the experiment, parents will rate their child’s level of interest in real guns using a 5-point scale 
(1=no interest to 5=very interested), as in previous research.viii 
Guns in the Home 
We will record the number of guns in the home. If there are guns in the home, we will record what types 
of guns they are, whether any guns are loaded, and whether any guns are locked up. 
 
Behavioral Measure of Aggression 
Experiments 1 and 2 will use a measure of aggression that has been successfully used for children about 
this age in our previous research.ix, x Participants will complete a 25-trial competitive reaction time task 
with an ostensible partner of the same sex in which the winner can blast the loser with loud noise 
through headphones. The noise is a mixture of noises that most people hate (e.g., fingernails scratching 
a chalkboard, dentist drills, sirens). The noise levels range from Level 1=60 decibels to Level 10=105 
decibels (about the same level as a fire alarm). Participants will be told that lose levels 8, 9, 10 can cause 
“permanent hearing damage to their partner.” xi The noise levels are well within Occupational Safety and 
Health Administration (OSHA) safety levels (i.e.,120 decibels). The threshold of pain for the human ear is 
140 decibels. Because decibels are measured on a logarithm scale, level 105 decibels is unpleasant but 
not painful or harmful. A non-aggressive no-noise option (Level 0) is also provided. The winner can also 
determine the duration of the loser’s suffering by controlling the noise duration (Level 1=0.5 sec to Level 
10=5 sec). The participant wins half of the trials (randomly determined). The ostensible partner set 
random noise intensities and durations across the 25 trials. Basically, within the ethical limits of the 
laboratory, participants control a weapon that can be used to blast their partner with unpleasant noise. 
A through debriefing will follow that we have successfully used in previous studies in which children are 

exposed to violent media. The parent will also be present during the debriefing. The researcher will read 
the debriefing to the child and answer any questions he or she has. 
 
For each of the dependent variables, we predict a main effect for violent content, a main effect for the 
presence of guns, and an interaction between violent content and the presence of guns. Specifically, we 
predict the highest levels of pro-gun attitudes and aggression among participants who see a violent clip 
containing guns. 
 
Power Analysis 
A power analyses revealed that 64 participants per group are needed to detect a medium sized effect at 
the .05 significance level with power=.80. Thus, the experiment requires 192 participants 
 
We aim to use ResearchMatch.org, a national electronic, web-based recruitment tool created through 
the Clinical & Translational Science Awards Consortium in 2009 and is maintained at Vanderbilt 
University (see ResearchMatch General Description.pdf). The Vanderbilt IRB provides oversight for 
ResearchMatch as a recruitment tool, and locally is managed by Rose Hallarn and the Center for Clinical 
& Translational Research at OSUMC. Individuals in the Columbus area who have self-identified or have 
identified their children as interested in participating in research studies will be identified through a 
targeted search using approved inclusion criteria (ages 8-12yo, willing to travel to the Ohio State 
University campus). A feasibility search using ResearchMatch with these criteria yielded 90-100 
adolescents available for recruitment. Once approved, investigators will send a message to identified 
individuals about the available study (see ResearchMatch Recruitment Message.docx). We will also 
recruit participants through other means (e.g., ads placed on craigslist, Facebook, newspapers) 
 
Internal Validity 
Because all studies are laboratory experiments, threats to internal validity are low. 

Statistical Analysis Plan 
 
Data will be collected in three ways: parental consent is collected directly by Qualtrics; the participants’ 
survey responses are done by hand on paper, and the participants’ handling of the handguns is recorded as 
video. After the conclusion of the study, the paper responses will be uploaded by the research staff into a 
Qualtrics survey. The videos will be content analyzed by trained research assistants who observe the 
participants’ behavior, verify the trigger pull count, and note if the trigger is depressed while the handguns 
are pointed at oneself or the other participant. At this point, the data can be merged into a single dataframe 
for validation and cleaning. Cleaning will be done in Excel and R. 
 
Once the data has been cleaned, the variables will each be examined via summary statistics and visually. If 
necessary, variables will be transformed to conform to the assumptions of the statistical tests, the 
Cronbach’s alpha of the survey batteries will be calculated, potential outliers will be identified, and 
preliminary bivariate and chi-squared tests will be run on the outcome variables. In addition, the three 
conditions will be tested for differences in the subjects along the measured variables. 
 
After this, the dataframe will be imported into STATA to perform a generalized estimated equation (GEE) 
with an exchangeable correlation structure was used to analyze data, with pairs as unit of analysis. All 
outcome variables will be measured with a negative binomial log-link model. First, each outcome variable 
will be tested with the condition as the sole predictor variable. Next, each control variable (trait aggression, 
attitude toward guns, etc.) will be tested along with the condition. Finally, the full model will include 
condition and all of the control variables. The research team will find the model of best fit, though only the 
reduced (condition only) and full models (condition, gender, age, whether the participant had taken a 
firearm safety course, if there is a firearm in the home, attitudes toward guns, trait aggression, consumption 
of violent media, parental estimation of child’s interest in firearms) will be reported. 
 
In addition, data on the participants’ familiarity with, opinion of, and performance in Minecraft will be 
recorded, primarily to verify that the participants don’t significantly differ between conditions. However, 
exploratory testing will be done to determine if these variables also have a significant impact on the 
outcome variables. Whether the participant played or watched the game will also be tested. 
 
 
 
 
i Bushman, B. J. (in press). The weapons effect. JAMA Pediatrics. 
ii Carlson, M., Marcus-Newhall, A., & Miller, N. (1990). Effects of situational aggression cues: A 
quantitative review. 
Journal of Personality and Social Psychology, 58, 622–633. 
iii Bushman, B. J., Jamieson, P. E., Weitz, I., & Romer, D. (in press). Gun violence trends in movies. 
Pediatrics 
iv Dal Cin, S., Stoolmiller, M., & Sargent, J. D. (2012). When movies matter: Exposure to smoking in 
movies and changes in smoking behavior. Journal of Health Communication, 17(1), 76-89. 
v Wills, T. A., Sargent, J. D., Gibbons, F. X., Gerrard, M., & Stoolmiller, M. (2009). Movie exposure 
to alcohol cues and adolescent alcohol problems: a longitudinal analysis in a national sample. 
Psychology of Addictive Behaviors, 23(1). 23- 25. 
vi Shapiro, J. P., Dorman, R. L., Burkey, W. M., Welker, C. J., & Clough, J. B. (1997). 
Development and factor analysis of a measure of youth attitudes towards guns and violence. 
Journal of Clinical Child Psychology, 26 (93), 311-320. 
vii Shapiro, J. P. (2000). Attitudes Toward Guns and Violence Questionnaire: Manual. Los Angeles, 
CA: Western Psychological Services. 

 
 
viii Jackman, G. A., Farah, M. M., Kellerman, A. L., & Simon, H. K. (2001). Seeing is believing: What 
do boys do when they find a real gun? Pediatrics, 107(6), 1247-1250. DOI: 10.1542/peds.107.6.1247 
ix Konijn, E. A., Nije Bijvank, M., & Bushman, B. J. (2007). I wish I were a warrior: The role of 
wishful identification in effects of violent video games on aggression in adolescent boys. 
Developmental Psychology, 43(4), 1038-1044. doi: 10.1037/0012-1649.43.4.1038 
x Gabbiadini, A., Riva, P., Andrighetto, L., Volpato, C., & Bushman,, B. J. (in press). Moral 
disengagement moderates the effect of violent video games on self-control, cheating and 
aggression. Social Psychological and Personality Science. 
xi Konijn, E. A., Nije Bijvank, M., & Bushman, B. J. (2007). I wish I were a warrior: The role of 
wishful identification in effects of violent video games on aggression in adolescent boys. 
Developmental Psychology, 43(4), 1038-1044. doi: 10.1037/0012-1649.43.4.1038