Summary: A new laboratory study finds that alcohol both raises people’s tolerance for pain and increases their willingness to harm others. Participants who consumed alcoholic beverages reported higher pain thresholds and were more likely to administer stronger and longer electric shocks to an ostensible opponent during a competitive task, compared with participants who received a placebo. The results suggest that alcohol’s numbing effect can blunt empathy for others’ pain and thereby contribute to aggressive behavior.
Researchers conducted two independent experiments using the same procedures to test whether alcohol-induced increases in pain threshold help explain why intoxicated people are more aggressive. Together the experiments included 870 adult participants who regularly consumed three to four drinks per occasion. Participants were randomly assigned to receive either an alcoholic or a placebo beverage, had their personal pain threshold measured with brief electric shocks, and then took part in a reaction-time task where “winners” chose the intensity and duration of shocks given to a supposed opponent. The study found that alcohol raised pain thresholds, and that those with higher pain thresholds were more likely to inflict greater and longer shocks.
Key Findings
- Alcohol increases pain tolerance, which is associated with reduced empathy and greater aggression.
- Participants who drank alcohol chose higher shock intensities and longer durations during the competitive task, and this aggressive behavior correlated with their elevated pain thresholds.
- Participants who drank placebo beverages generally retained greater sensitivity to pain and were less aggressive toward the ostensible opponent.
Study details and methods
The research used a well-established experimental paradigm adapted for humans. Two independent laboratory experiments were run with identical methods: Experiment 1 included 543 participants and Experiment 2 included 327 participants. All volunteers reported that they drank socially at the specified levels and were recruited by advertisement and compensated for participation.
After providing informed consent, participants had 20 minutes to consume either an alcoholic beverage or a taste-matched placebo. The placebo drinks were prepared to mimic the aroma and taste of alcohol by placing a small amount of alcohol on the surface and around the rim of the glass, while the bulk of the drink was nonalcoholic orange juice. This procedure was designed to keep participants unaware of their condition.
Following consumption, each participant received successive one-second electric shocks to two fingers on one hand. Shock intensity increased stepwise until the participant labeled the sensation as “painful”; that point was recorded as their personal pain threshold. Participants then completed a competitive reaction-time task in which winners could deliver shocks to the loser. In reality, there was no live opponent: outcomes were predetermined so that each participant “won” half of the trials. Shock intensity options ranged from 1 (low) to 10 (the level each participant had identified as painful), and participants also selected shock duration. The summed intensity and duration across trials served as the aggression measure.
Results and interpretation
Across both experiments, participants who consumed alcohol reported higher pain thresholds than those who received the placebo. Importantly, higher pain thresholds predicted stronger and longer shocks selected during the competitive task. In short, the less participants felt their own pain after drinking, the more pain they were willing to inflict on another person. Participants who received placebo beverages were generally more sensitive to pain and correspondingly less aggressive.
Study co-author Brad Bushman of The Ohio State University emphasized that when intoxicated people cannot easily gauge their own discomfort, they may become less sensitive to others’ pain and therefore more likely to behave aggressively. In this study, average blood alcohol concentrations among the alcohol group ranged from approximately 0.095% to 0.11%, slightly above the legal driving limit used in many jurisdictions. The authors note that larger doses of alcohol might produce even greater increases in pain threshold and aggression.
Funding and authorship
The research was supported by the National Institute on Alcohol Abuse and Alcoholism and the National Center for Research Resources. Co-authors include C. Nathan DeWall and Peter Giancola, alongside Brad Bushman.
About this AUD, aggression, and psychology research news
Author: Jeff Grabmeier
Source: Ohio State University
Contact: Jeff Grabmeier – Ohio State University
Image: Image credited to Neuroscience News
Original research: “Too Insensitive to Care: Alcohol Increases Human Aggression by Increasing Pain Threshold” by Brad Bushman et al., published in the Journal of Studies on Alcohol and Drugs. (Closed access)
Abstract
Too Insensitive to Care: Alcohol Increases Human Aggression by Increasing Pain Threshold
Objective: Alcohol has long been used to dull physical and emotional pain. Prior studies report that alcohol raises pain threshold and that higher pain thresholds are associated with greater aggression. This research tested whether alcohol’s tendency to increase pain threshold helps explain its link to aggressive behavior.
Method: Two independent laboratory experiments were conducted to replicate findings (Experiment 1: N=543; Experiment 2: N=327). Male and female heavy social drinkers were randomly assigned to consume either an alcoholic or a placebo beverage. Pain thresholds were measured with stepwise electric shocks until participants reported the sensation as “painful.” Participants then delivered shocks to an ostensible opponent during a competitive reaction-time task; shock intensity and duration were standardized and summed across trials to produce an aggression measure.
Results: Participants who consumed alcohol had higher pain thresholds than those who consumed placebo. Across both experiments, higher personal pain thresholds predicted greater aggression, measured by the intensity and duration of shocks delivered to the ostensible opponent.
Conclusions: The findings provide evidence that one pathway linking alcohol to aggression is its effect on increasing pain threshold. When people feel less of their own pain due to intoxication, they may become less empathetic toward others and more likely to inflict harm.