Sunday, March 31, 2024

The Weapons Priming Effect: A Brief History and a Word of Caution

After Carlson et al. (1990) published their meta-analysis, the weapons effect was considered an established phenomenon. Short-term exposure to weapons appeared to increase the level of aggressive behavioral responses in lab and field settings compared to short-term exposure to neutral stimuli. After 1990, there has been a dearth of research examining the effect of weapons on aggressive behavioral outcomes. Instead, there appeared to be a shift to examining the cognitive underpinnings of the weapons effect. Although there were a couple experiments in which participants were administered a Thematic Apperception Test (TAT) arguably as an attempt to assess if participants thought more aggressively when exposed to weapons (e.g., Frodi, 1975), it would not be until the 1990s until a small group of social psychologists would more explicitly assess if the mere exposure to weapons or weapon images primed aggressive cognition utilizing techniques pioneered by the Cognitive Revolution in psychology. 

By the mid-1990s, some aggression researchers were using schema or associative network theories as a means to understand the impact of various aggression-inducing stimuli on aggressive cognition, affect, and behavior. Craig Anderson, for example, was already developing a theory known at the time as the General Affective Aggression Model (GAAM), shortened to General Aggression Model (GAM; Anderson & Bushman, 2002) by the start of this century. In that model, individuals store aggression-related information in the form of cognitive schemas and behavioral scripts. Exposure to stimuli theoretically believed to be associated with aggression or violence would prime these schemas or scripts, leading to an increased accessibility of aggressive thoughts, and potentially leading to an increase in aggressive behavioral responses. One interpretation of the classic Berkowitz and LePage (1967) weapons effect experiment was that those participants in the control room containing rifles were primed to think more aggressively and hence, under high levels of provocation, respond more aggressively.

The first explicit effort to test for a weapons priming effect was in the dissertation of Deuser (1994), a student of Craig Anderson. The experiments in that particular dissertation did not demonstrate a weapons priming effect at all. It did not matter whether participants were exposed to weapons or neutral stimuli. There was no evidence to support the theory that weapons would prime aggressive thoughts. The first published evidence of a weapons priming effect was Anderson et al (1996), although the weapons priming effect was more secondary to the main purpose of the article, which was to establish the General Aggression Model as a theory and to test the effects of uncomfortable heat on aggressive cognition, affect, and attitudes. The weapons priming effect was tested on those participants who were not exposed to uncomfortable heat. Participants were exposed to either weapon or neutral object images and were given a Stroop test to assess accessibility of aggressive cognition. Participants primed with a gun had more aggressive thoughts than those primed with a neutral object. The effect was fairly small, which seems to be a theme with this line of research, but definitely noticeable. 

That finding by Anderson et al (1996) was promising. The next step was to examine if weapons truly semantically primed aggressive thoughts. Anderson et al (1998) conducted two experiments. This is where I and Bruce Bartholow (both graduate students at University of Missouri at the time) come in. I had already been exposed to the schema and script theories described in the article's introduction, which helped designing experiments considerably. I did a lot of the legwork to find a reasonably sensitive measure of accessibility of aggressive cognition, and eventually settled on a version of the pronunciation task, in which participants read the target word into a microphone, and the time it takes between onset of stimulus and when participants' voices are picked up on the microphone is measured in milliseconds. For our purposes, participants demonstrated relative accessibility of aggressive thoughts if they reacted faster to aggressive target words than non-aggressive target words. The only difference between our two experiments were the stimuli. In Experiment 1, the prime stimuli were weapon words versus animal words. In Experiment 2, the prime stimuli were a mix of weapon images or a mix of neutral images. We had participants go through a few blocks of trials in which participants would first see the prime and then speak into the microphone when they saw the target word. So participants would first see a weapon (word or image) or neutral (word or image) concept and then saw an aggressive or non-aggressive target word, which they pronounced into the microphone as quickly and accurately as possible. We expected participants to show the fastest reaction times when weapon primes were paired with weapon target words. In each experiment, our expectations were confirmed. The effect size for Experiment 1 was in between small and medium, and in Experiment 2 closer to that of Anderson et al (1996). 

Since the publication of Anderson et al (1998), there have been several successful efforts to replicate and in some cases extend that finding. The dependent variables may differ (e.g., lexical decision task, aggressive word completion task or AWCT), and the experimental design may either be between-subjects or within-subjects, but the basic concept is the same. Bartholow et al (2005) in Experiment 2 started out as a replication and extension, and initial drafts of the manuscript included the analysis demonstrating the replication of Anderson et al (1998). That analysis was deleted in the published version. Thankfully, I kept the file with the analyses, although I don't have the original data file any more. There is a story behind the delay between when we ran our experiments and publication date, but that was more of an error by the editor, and can be chalked up to what life was like before electronic submissions of manuscripts. The effect was smaller than in any successful experiment up to that point, but still statistically significant. I think of the cognitive experiment by Lindsay and Anderson (2000) as a solid conceptual replication. Bartholow and Heinz (2006) would also offer a good faithful replication as a means of demonstrating that the concept of alcohol had a similar effect on relative accessibility of aggressive cognition. Subra et al (2010) would offer a conceptual replication of Bartholow and Heinz (2006). Bushman (2017) and Benjamin and Crosby (2019) also successfully replicated and extended the Anderson et al (1998) experiments. 

This seems like a fairly rosy picture. But here is where I start to have concerns. Every experiment I have mentioned thus far involves either Anderson or Bushman or their associates or former advisees. I have blogged before about experimenter allegiance effects before in the context of understanding the discrepancy between findings Berkowitz and his various colleagues and independent researchers who failed to replicate a weapons behavioral effect, including the Buss et al (1972) direct replication attempt. One of my concerns is that we may have a similar phenomenon with our weapons priming effect research, but there has been almost no work done to independently try to replicate our findings. The Anderson et al (1998) paper is one I am still proud of, and it is cited fairly frequently even today. But there is a problem. Almost anyone who is independent of our cohort of researchers uses that paper as a means of justifying their own experiments on phenomena that are often entirely divorced from our research. There may be an allegiance effect that we are missing. Most experiments outside of the Anderson-Bushman cohort that could arguably be coded as weapons priming experiments are often secondary to the main thrust of the published papers or use dependent variables that could defensibly be used as proxies of aggressive cognition, although reasonable skeptics would certainly have questions and might challenge any judgment that the measures involved are truly proxies of aggressive cognition. At least one experiment that was purported to be a conceptual replication of Anderson et al (1998) was later retracted due to the research and data analyses being fundamentally flawed, if not outright fraudulent (see Zhang et al, 2016, which I've written about before). I've seen one successful independent replication of Bartholow et al (2005) that used a somewhat defensible dependent variable (Korb, 2016). Regrettably, publication never came to fruition.

We are left with a cohort of weapons priming effect researchers who have almost exclusively used the GAM as a theoretical model (which is itself deserving of challenge), and may have produced experiments that are unique to our particular cohort. Independent researchers might take our protocols and find something entirely different. Such researchers may find different and arguably better ways to test the same hypotheses we tested. Unfortunately, there appears to be no way to know, unless or until enough aggression researchers come forward and report their own replication attempts either as preprints or as publications. If independent researchers find something different to what my group of researchers found, I think that would be interesting and worth understanding. I would want to know what was different. It is possible and likely probable that independent researchers would consider things we would not have considered? How that would impact the overall body of weapons priming research is very much unknown. It could we be the case that there was just something unique about any of us who studied the weapons priming effect who were either Anderson or Bushman and their various students/associates and that our findings can be safely ignored moving forward. All I know is that the findings from an experiment I conducted back at the start of my doctoral career (Anderson et al, 1998, Experiment 2), are in line with the overall effect size for aggressive thoughts that I reported in a meta-analysis (Benjamin et al, 2018).  With regard to that meta-analysis, I will gladly defend any coding decisions made in collaboration with my third author, even if we clearly differ in how to interpret our findings once we had ascertained that the analyses of effect sizes were sound. 

One final thought. Although I was trained via the GAM theoretical model, I am not wed to it. I think a good case could be made that the weapons priming effect is little more than a cognitive response equivalent to classical conditioning, and that outside of possibly cognitive responses, there isn't a whole lot left to write about. I've said that in some other contexts, so I'll say it here. There are theorists (including philosophers) who are trying to place the whole body of weapons effect research into different theoretical frameworks. Their work is worth examining. 

In the meantime, I am very concerned that my particular line of weapons priming effect research is little more than an experimental allegiance effect. I won't know more unless or until other independent researchers come forward. If their findings are consistent enough with what I and my cohort found, that's swell. We've at least established a cognitive response to what should be an aggressive-inducing stimulus. If not, aggression researchers like me need to go back to the drawing board. That is also okay. From my own perspective, I made my peace with this line of research several years ago. I started siding with the skeptics for a reason, and that was because the skeptics had the better argument on matters of theory and on the findings themselves. With regard to the weapons effect, or the weapons priming effect, I started out without a horse in that race. I will likely end my career without a horse in this race. Turns out there is nothing wrong with that.