A recent study sheds light on the connection between alcohol consumption, pain tolerance, and aggression, suggesting that alcohol’s ability to numb physical pain may play a significant role in why intoxicated individuals are more prone to aggressive behavior. Recently in the Journal of Studies on Alcohol and Drugs, the findings indicate that the less pain participants experienced after drinking alcohol, the more likely they were to inflict pain on others.
Prior research has consistently demonstrated that alcohol increases the likelihood of aggressive behavior, but the exact reasons for this effect remain elusive. Researchers Brad Bushman and his colleagues proposed that alcohol’s pain-numbing properties could diminish empathy, making individuals less sensitive to the suffering of others. This hypothesis aligns with the idea that feeling one’s own pain is essential to understanding and responding to others’ discomfort.
“For over 30 years I have studied risk factors for aggression and violence. Alcohol is an important risk factor,” said Bushman, a professor of communication at The Ohio State University.
To test their hypothesis, the researchers conducted two experiments with a total of 870 participants, all healthy social drinkers aged 21 to 35. Participants were recruited through advertisements and compensated for their time. Individuals with serious mental illnesses, alcohol or drug dependencies, or other disqualifying conditions were excluded to ensure the sample represented typical social drinkers.
Each participant was randomly assigned to consume either an alcoholic or placebo beverage. Men in the alcohol group received a dose of alcohol mixed with orange juice equivalent to 1 gram of alcohol per kilogram of body weight, while women received a slightly lower dose to account for physiological differences. Placebo drinks contained only a minimal amount of alcohol to simulate the sensory experience without causing intoxication.
Once the beverages were consumed, participants underwent a pain threshold test. This involved receiving brief electric shocks that gradually increased in intensity until the participant indicated the sensation had become painful. For those in the alcohol group, the test began 15 minutes after drinking to allow time for the alcohol to take effect, while the placebo group completed the test shortly after finishing their beverages.
Participants then engaged in a competitive reaction-time task, a well-established method for measuring aggression in laboratory settings. In this task, participants competed against a supposed opponent, with the winner able to administer an electric shock to the loser. They could control the shock’s intensity and duration, with higher levels corresponding to the participant’s pain threshold. Unbeknownst to them, the “opponent” was an accomplice who deliberately escalated the shocks they appeared to administer, encouraging participants to retaliate.
The findings revealed a clear pattern. Participants who consumed alcohol had a higher pain threshold than those in the placebo group, consistent with the known analgesic effects of alcohol. More importantly, this reduced sensitivity to pain was linked to increased aggression during the competitive task. Participants in the alcohol group administered higher-intensity shocks for longer durations compared to their placebo counterparts, and their willingness to inflict pain correlated with their own diminished ability to feel it. These results were replicated across both experiments.
“It is already well-known that alcohol increases aggression and that alcohol numbs pain,” Bushman told PsyPost. “This is the first study to link those two well-known findings. One reason alcohol increases aggression is because it increases people’s pain threshold.”
“I was surprised by how consistent the findings were. Scientists like to replicate their studies to make sure they are reliable. We found almost identical results in two very large studies.”
But there are still some caveats to consider. For instance, the findings only partially explained the relationship between alcohol and aggression, as pain tolerance accounted for roughly 20% of the observed effects. This suggests that other factors, such as impaired judgment or reduced empathy, also contribute to intoxicated aggression.
“There are many possible reasons alcohol increases aggression,” Bushman noted. “Increasing one’s pain threshold is not the only reason.”
Additionally, the study focused on moderate doses of alcohol and interactions with strangers, leaving questions about whether higher doses or conflicts involving close relationships might produce different outcomes.
Future research could address these limitations by exploring other potential mediators of alcohol-induced aggression, such as emotional regulation or social dynamics. Examining individual differences, including personality traits or histories of trauma, might also shed light on why some individuals are more prone to aggression when intoxicated.
Regarding the long-term goal of this line of research, Bushman said he hopes “to make the world a more peaceful place!”
The study, “Too Insensitive to Care: Alcohol Increases Human Aggression by Increasing Pain Threshold,” was authored by C. Nathan DeWall, Peter R. Giancola, and Brad J. Bushman.
