The science of aggression

When it comes to the use of force, officers are making decisions so incredibly complex and swift that it is impossible to know all of the intricacies in retrospect


Policing is a practice bounded by rules of physics, biology and law. Managing human behavior, including use of force, requires an understanding of how the brain functions, how perception is translated through the senses, the biochemistry of fear, the limitations of human performance, the principles of leverage, friction, reaction time and other basic laws of physics.

Therein lays the knowledge gap between the police officer and the armchair commentator. The observers simply don’t grasp the science.

The boundaries of time

We often glibly talk about “split-second” decisions, but the truth of that statement is more severe than most realize. (Photo/Police1)
We often glibly talk about “split-second” decisions, but the truth of that statement is more severe than most realize. (Photo/Police1)

We often glibly talk about “split-second” decisions, but the truth of that statement is more severe than most realize.

In baseball, a batter has 55 feet between home plate and the pitcher’s mound. At a moderate 70 mph pitch, the ball will be at the batter in less than ½ a second. This time exceeds the average reaction time of a human, so skilled batters begin their swing based on a variety of factors, but never based on when the ball is present within their reach. A quarterback has the immense luxury of about three seconds to decide what to do with the football before getting sacked.

According to statistics compiled by the FBI on officer deaths, the most frequent distance between an assailant and the murdered officer is less than five feet, with most within 10 feet, and over 80% less than 50 feet. The decision to use deadly force – whether by a suspect or a law enforcement officer – is always measured in milliseconds.

According to research published by the National Institute of Health, “Factors that can affect the average human reaction time include age, sex, left or right hand, central versus peripheral vision, practice, fatigue, fasting, breathing cycle, personality types, [and] exercise.”

And, despite our decisional training often being referred to as “shoot/don’t shoot,” those decisions are not binary. No less than the quarterback or homerun hitter, an officer is making multiple calculations while everything they observe is in a state of change. Those decisions are so incredibly complex and swift that it is impossible to know all of the intricacies in retrospect.

The boundaries of perception

The human eye is not all-seeing. Our brain manages to execute a lot of short-cuts to keep us from being overwhelmed with sensory input. Anyone who has ever watched a movie realizes that the motion on the screen is an illusion from a rapid presentation of photos. Magicians are the keenest experts in making us "see" things that aren't there by setting up distractions or expectations that suit their purposes.

We have templates through which we experience our sensory inputs. A toy gun that looks like a real gun will be perceived as a deadly threat. A cell phone, when presented like a gun would be pointed and unlike a cell phone would be, will be perceived as a deadly threat. If an officer gets a citizen description of a red-headed suspect wearing a green shirt, a redhead in anything resembling a green shirt will be considered a suspect. 

Most importantly, a responding officer cannot control the perceptions of those they are contacting. If a badge is considered the mark of an enemy, or a threat to a parolee’s liberty, or a drug-induced image of a fire breathing dragon, the officer will have very little time to manage that perception.

The boundaries of biochemistry and human performance

What a person perceives, how their brain interprets it and what behavior results is a chain of body chemistry. The primitive brain, whose job it is to respond to perceived threats, has been licensed by nature to take over the neuromuscular system. If that part of the brain sets off the alarm, a cascade of chemistry sets off the chain of events known as fight, flight, or freeze. That body chemistry muddles rational thinking and reverts to instinct and conditioning. The calming process takes time.

It is important to note that the fight/flight chemical cascade can be activated by threats to one’s ego, sense of self, status and personhood, as well as threats to one’s body or safety. Aggression and non-compliance can manifest from a multitude of origins. Add to these mental states the reality that persons under the influence of alcohol or other drugs, including some therapeutic drugs, are prone to aggression. Mental illness, poor nutrition, poor socialization, low emotional intelligence, low verbal skills, and a history of violence in the home or origin are all related to aggression and violence.

“What we think is that the threshold to explode is probably regulated by various neurobiological features. The baseline state of aggression also may be related to baseline neurobiological features, but also what’s going on in the environment, because the neurobiological features that send someone to exploding aggression are there all the time,” according to Emil F. Coccaro, MD. “It actually is a complex triad of emotion, cognition and behavior. The emotion is anger, the cognition is hostility, and the behavior is aggression.”

There is no de-escalation easy button.

The boundaries of context

As interesting as the science knowledge deficit is among critics, they do seem to hold to the one supernatural belief of ESP, or extra-sensory perception. That is, the offending officers should have known all of the things that reporters dig up in the aftermath.

Officers are limited in their knowledge of circumstances when responding to a call or even an event that they view in progress. Their information comes from what they know about their patrol area, what the dispatcher tells them, what they know about the persons involved and what they know about the behavior of people in similar situations in their experience. Officers are no better at predicting the future than quarterbacks and batters whose best expectations are often thwarted. Fortunately, the courts are much more objective in judging what the officer knew or should have reasonably known at the moment of decision.

All of the body-worn cameras and cell phones in the world can never replicate what an officer perceives while dealing with persons they contact. Only a thorough and scientific investigation can begin to reveal the truth about violent encounters between law enforcement and those with whom they interact with rare violent outcomes. Before knowing all the knowable facts of a case no critic should be taken seriously.

NEXT: 'I didn't kill him – and nobody cared'

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