Weapons effect

Weapons effect is a theory in social psychology that the mere sight of a weapon causes aggression levels to increase, especially when an individual is angry. Researchers Leonard Berkowitz and Anthony LePage, who coined the phrase “weapons effect,” first tested the theory in 1967, finding that aggression increased in aroused individuals who had seen guns. The landmark study has been criticized by social psychologists who contend that many factors other than weapons influence whether an individual becomes aggressive, such as family history and temperament. Some subsequent studies replicating the initial experiment have yielded similar results, but others have not.

Background

In their landmark 1967 study, Berkowitz and LePage recruited one hundred male University of Wisconsin students to participate in the experiment. (Participants in these studies are usually male because most perpetrators of violent crime are male.) The researchers seated the participants at tables in different rooms. Some had a gun and a revolver on their table, while others had badminton racquets. All participants were told to ignore the items on the tables because they were left there from a previous experiment and should have been put away.

The participants then randomly received either one shock or seven shocks from a peer. The students who received the shocks were then permitted to give their peers as many shocks as they pleased. The greatest number of shocks came from participants who had received seven shocks and also seen the guns on the table. Berkowitz and LePage noted that subjects displayed aggressive behavior only when both variables were present: the seven shocks and the weapons. They described their experiment in “Weapons as Aggressions-Eliciting Stimuli,” published in the Journal of Personality and Social Psychology.

Overview

Many researchers have attempted to replicate the weapons effect theory. In 1971, researchers Monte Page and Rich Scheidt replicated the 1967 experiment conducted by Berkowitz and LePage, but only under certain conditions. They obtained the weapons effect with participants who were somewhat sophisticated and aware of the purpose of the guns. The subjects also had to be experiencing little or no apprehension related to the experiment. Those who were apprehensive did not act in a way that supported the original study.

One of the strongest criticisms of the weapons effect was made in 1974 by H.D. Schmidt and A. Schmidt-Mummendey. They concluded that no correlation existed between the sight of weapons and levels of aggression. They attributed the weapons effect to the result of operant conditioning, making an association between an object and a behavior. They published their findings in the article “Weapons as Aggression-Eliciting Stimuli: A Critical Inspection of Experimental Results.”

Another experiment was conducted by Ann Frodi in 1975 in Sweden. Frodi generally followed the same procedure as Berkowitz and LePage. She recruited one hundred male high school students. Her participants were shown either weapons, no weapons, or a baby bottle, which was thought to inhibit aggression. Her subjects were shocked by a peer and then permitted to shock the peer. While the shocks angered some participants, they did not anger others.

Frodi found that the most aggressive participants had seen the weapons, but anger did not come into play. Those shown no weapons and those shown a baby bottle did not significantly differ in the number of shocks they administered, leading Frodi to conclude that the baby bottle did not affect participants.

Some experiments have also been conducted to expand on the weapons effect theory. In 1998, researcher Craig Anderson and his colleagues wanted to see if weapon-related words and images of weapons would make participants more aggressive. Anderson performed two experiments: In the first, he recruited thirty-five male and female undergraduate students. Half saw weapon-related words on the screen, and half saw animal-related words. The second experiment consisted of a group of ninety-three undergraduate students. Half saw images of weapons, and half saw images of plants. The experiments showed that reading weapons-related words or seeing images of weapons increased reading speed, indicating that participants had become agitated.

In 2005, B.D. Bartholow and colleagues extended the weapons effect theory by testing whether knowledge about guns affected aggression. They conducted several experiments with hunters (with gun knowledge) and non-hunters (with no gun knowledge). Those with gun experience became more aggressive when shown assault rifles than hunting rifles, possibly because an assault rifle has greater killing capacity. This reaction also occurred when hunters were shown pictures of guns.

An experiment in 2006 supported the weapons effect theory and also found that aggressive impulses are strong enough to override common sense. Drivers in the study were confronted with a pickup truck driver who was stalled at a green light. Half the drivers saw a pickup truck with a rifle in it, while the other half saw just a pickup truck. Drivers were more likely to honk their horns at the pickup truck with the rifle, even though such a reaction might be dangerous.

While understanding if or how weapons increase aggressive thoughts might help curb or even prevent violent crime, the mixed results of the studies make this application unlikely. The original 1967 study cannot be replicated in the twenty-first century because ethical standards are much higher than they were in the past. Social psychologists would not be allowed to administer electrical shocks to participants or inflict any type of pain on them. Furthermore, since most of these studies were performed in laboratories, it is unclear if they would be applicable in the real world.

Further, research attempting to replicate the weapons effect based on online examples failed to reproduce past findings, and some experiments showed an anti-weapons effect: some subjects were better able to identify or describe a perpetrator when a weapon was present than when it was absent. Analyzing data from five experiments using a random-effects meta-analysis, researchers found that the weapons effect had an insignificant impact on participants' memory of perpetrator descriptions and identification. This led to the conclusion that the effect is either not replicable or is highly dependent on study methodology.

Bibliography

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Körner, Hannes M., et al. “Is a Knife the Same as a Plunger? Comparing the Attentional Effects of Weapons and Non-Threatening Unusual Objects in Dynamic Scenes.” Cognitive Research: Principles and Implications, vol. 9, no. 1, 2024, p. 66, doi:10.1186/s41235-024-00579-1. Accessed 25 Nov. 2025.

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Mac, Ryo. “The Weapons Effect—Does the Mere Presence of a Gun Increase Aggression?” Skeptikai, 12 Sept. 2016, medium.com/skeptikai/the-weapons-effect-does-the-mere-presence-of-a-gun-increase-aggression-c13c1b32e8aa. Accessed 25 Nov. 2025.

McLeod, Saul. “Eyewitness Testimony in Psychology.” Simply Psychology, 15 June 2023, www.simplypsychology.org/eyewitness-testimony.html. Accessed 25 Nov. 2025.

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