In a series of experiments, mice that watched others fight showed brain patterns similar to those of better fighters without direct participation, potentially paving the way for programming human brains to fight like Neo in the movie The Matrix.
The Princeton research team behind the study also found that the changes were not permanent, with the trained mice losing their enhanced fighting abilities within a few days after the experiments were completed. This finding suggests that observational training may need to be reinforced in ways similar to traditional training methods.
Enter the Matrix: Programming the Brain to Fight Starts with Observation
To determine if mice could learn how to fight by watching others in combat without participating, the researchers assigned selected male mice to three groups: fighters, spectators, and novices. Fighters spent the eight-day trial period participating in three daily “training” sessions lasting approximately 10 minutes. This included a daily sparring session with a “pushover” mouse, an easily defeated opponent.
During the fights, the mice assigned to the spectators group viewed the action from a raised platform. This observation point included a clear barrier, providing the mice with a safe, unobstructed view of the combat below. The spectator perch also allowed the mice to hear and smell the combat while preventing them from joining the melee. As a control, the novice mouse group spent the ten-minute training sessions playing with a similarly sized stuffed toy mouse and did not witness any fights.
After the eight-day trial period, all mice spent the ninth day fighting what the researchers termed “hard-to-beat” opponent mice. These fights involved three rounds of four minutes each. Jorge Iravedra-Garcia, a postdoctoral scholar and lead author of the paper, filmed their behavior throughout the process, allowing the team the opportunity to analyze each interaction in greater detail.
Spectators Learned to Move Like Fighting Mice
When analyzing the behavior of the spectator mice, Annegret Falkner, assistant professor of neuroscience at Princeton and senior author of the paper detailing the team’s work, said that they didn’t seem to care about the activity below them when the fighting animals “were just walking around and interacting.” However, the professor noted, when the attacks start, the team witnessed the spectator mice “orient and attend” the action.
“Even if an attack starts and they’re not oriented, they’re more likely than chance to turn and watch what’s happening,” Professor Falkner said, adding that something “very salient and sticky” about aggressive behaviors differs from other behaviors.
When the team studied the day nine fights involving all three mouse groups, they noted that the spectators appeared to have learned some fighting techniques. For example, fighter mice attacked tougher opponents more quickly than novice mice with no fighting experience. Notably, spectator mice mimicked this behavior, attacking tougher opponents more quickly than novice mice.
Fighting mice and spectator mice also spent less time with their backs turned to opponents, suggesting this was also a learned behavior. The team noted that the “choreography” between fighting mice and spectating mice was similar, and notably different than that of novice mice.
“Not only are they emulating some of these behaviors, but the way that they move between these behaviors is also quite similar,” Iravedra-Garcia said. “When you compute the transitions from aggression behavior one to investigation behavior two, experienced animals behave very similarly to observers in those situations as well.”
Notably, none of the groups spent more overall time attacking opponents. The research team said this result suggests that fighting or spectating did not make the mice inherently more violent.
Scans Show Similarities Between Mice’s Neurological Activity
During the experiments, the team tracked the brain activity of the three mouse groups. When they looked at the brains of the fighting mice and the spectators, they found several similarities. Iravedra-Garcia said that brain activity is “mirrored” in both previously studied brain areas related to aggression. For example, the inhibitory cells of the spectator mice’s brains fired in patterns “much like a fighter’s.”
Still, the team said the mirroring between the groups was not perfect. For example, when spectators watched fights, their brains’ excitatory activity more closely matched that of the novice mice’s brains. This changes somewhat during actual combat, but the team still noted that the match was not 100%, with Falkner noting that the spectator mice’s brains were “kind of midway between the truly experienced fighters and the naive animals.”
“There’s something about experience that gets you all the way there, but observation gets you in a similar direction, but only about halfway,” Falkner said, adding that “observation’s not a replacement for experience.”
“I Know Kung Fu!”: Learned Abilities May Be Directly Transferred Between Brains
When discussing potential applications of their findings, the researchers pointed to the possibility of encoding brain patterns gathered from actual fighters into the brains of inexperienced fighters, like Neo learning King Fu and other martial arts in the 1990s sci-fi classic The Matrix. Falkner suggested replaying the recorded brain activity down to the individual circuit level, “giving them the experience of watching, even though they never watched anything,” Falkner said.
“If you replay back this sequence of activity and then you test them, do they behave as if they actually watched a fight?” the professor asked.
The team noted that the experiments did not make any of the mice more aggressive or more violent, “just more prepared,” potentially contradicting fears about exposure to violence increasing violence. Although the original study was performed with mice, not human brains, Falkner also said he suspects some of the brain circuit changes observed in the experiments “are conserved in mice and humans.”
“I do think that it does suggest that if you were exposed to a lot of violence, you might have undergone circuit changes that create behavioral states that might be adaptive if you’re in a violent situation, but they’re probably not adaptive if you’re not in a violent situation,” the professor concluded.
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.