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How We Process Under Pressure: Stress, Perception and Cognition

Our psychology can change enormously in the forensic realm and elsewhere.

Key points

  • Modern research shows us what to expect, psychologically, when we experience extreme stress, such as that typical of many crime situations.
  • Heart rate is a key indicator of high stress but even very fit persons can experience very high heart rates under stress.
  • These factors can change our psychology enormously. Understanding these changes is essential in the forensic realm.

Forensic psychology frequently deals with nasty situations. The enormous stress of crime scene events can literally change the perceptual and cognitive processes of victims, suspects, and law enforcement officers alike, frequently with major consequences for criminal justice proceedings (e.g., Sharps, 2022).

Matthew J. Sharps
Source: Matthew J. Sharps

We dealt with some of these issues in a previous Forensic View (May 22, 2020), showing how high stress may reduce the blood-borne resources available to the prefrontal cortex, among other brain areas, with a corresponding reduction in specific aspects of human perception and cognition. But how stressed do we have to be for these factors to emerge?

Stress is not all bad. Healthy readers of this post probably have resting heart rates, in terms of beats per minute, somewhere in the 70’s or perhaps 80’s, with a few healthy people having heart rates somewhat higher or lower. However, that’s not enough of a heart rate to cope with the cardiovascular needs of forensically-relevant tactical situations. To increase our physical strength, speed, and endurance, our cardiovascular systems are primed to supply us with the blood-borne resources needed to cope with physical emergencies. Under these circumstances, we enter the fight-or-flight state regulated by the HPA Axis (the activity of the Hypothalamus, Pituitary, and Adrenal systems). Chronic fight-or-flight functioning can produce major physical and psychological problems, as detailed elsewhere (e.g., Sharps, 2022; Forensic View, 5/22/20). But over the short term, the enhanced blood flow provided by HPA activity (one of the major chemical products of which is adrenaline) gives us strength, speed, and endurance far beyond our everyday abilities.

However, to attain these heightened physical powers, we must raise our heart rates to the optimal “zone” for tactical, high-stress activity. This lies between 115 and 135 beats per minute according to most authorities.

In this heart rate “zone,” we are stronger and faster than normal; but there is a downside. As our hearts beat faster, we begin to lose our fine motor coordination. If you’ve ever seen an angry fisherman, with a correspondingly raised heart rate, attempting to untangle a knotted fishing line while inadvertently making the tangles even worse, becoming more enraged as a result and creating even more incomprehensible tangles, you’ve seen a good example of the fine-motor effects of a rage-based rise in heart rate.

As the heart rate rises even higher, we start to see increasingly severe consequences of the fight-or-flight state. We may experience problems with gross motor coordination, or with perception and cognition. Changes in hearing are seen. “Tunnel vision” increases. Reliance on ingrained habits, as opposed to new adaptive behaviors, becomes stronger, and we may report illusory changes in visual clarity and in the perceived passage of time. Our ability to remember accurately is diminished, and we may impulsively blurt out inappropriate and intrusive thoughts. We may experience dissociation; and at very high levels of stress, with heart rates perhaps in the 170’s, we may exhibit partial paralysis, inappropriately submissive behavior, and even loss of bowel and bladder control.

All very annoying; but as we will see in subsequent posts in the Forensic View, all of these fight-or-flight, HPA factors, however maladaptive today, were either adaptive or relatively benign in the ancient world.

Wait a minute. How could partial paralysis, submissive behavior, or loss of bowel and bladder control ever be adaptive?

Well, today, they aren’t. If a law enforcement officer today loses bowel or bladder control, it’s certainly not great for command presence. Especially in a khaki uniform.

Yet in the ancient world, when the adversary was not a human malefactor, but a great sabertooth cat with fabulous olfactory abilities, self-marination in our nastier biological byproducts may have rendered us far less appetizing; the sabertooth may have gone from “RARRGH!” to “EWWW!” in a few moments, leaving us unappetizing and uneaten, able to fight another day.

Partial paralysis? ‘Possums have been pulling that trick for millions of years, thwarting their would-be predators. Most mammals cannot tolerate the bacterial smorgasbord of the recently dead, so a motionless creature is often left untasted.

As to submission, in many species of canines and primates, a submissive posture may prevent further attacks.

These aspects of the human fight-or-flight response may have come in very handy for our remote ancestors facing sabertooth cats or dire wolves. In the modern world of gang members and homicide, perhaps not so much; but we are not only our present selves. We are also whatever our ancestors were in the past, provided the relevant characteristics found their way into our genomes. So, we may wet ourselves when facing a mugger, the same way our ancestors did when facing a short-faced bear.

Maybe these behaviors, under high stress, may have served prehistoric purposes, but let’s face it, how many of us ever approach a heart rate in the 170’s?

My friend and colleague, Professor Riccardo Fenici, has the answer.

Fenici and his colleagues (e.g., Fenici & Brisinda, 2004) studied fabulously fit young officers of the Italian federal police. These elite officers clocked in with heart rates in the low 60’s.

Then they went to the firing range.

This range involved only targets. Nothing was shooting back; the only possible hazard was that another officer might shoot better than you did, yet their heart rates rose into the 160’s.

That's a one-hundred-beat rise, in very fit young officers, deriving from nothing more than the stress of shooting competition.

Is 160 the same as 170? No, but it’s awfully close. Imagine what it might have been if the targets were shooting back, as we frequently see in real-world crime scenes.

Heightened HPA activity is a fact of life in the forensic world. It produces very specific perceptual and cognitive anomalies which are not rare, they are a major factor in the forensic analysis of virtually every violent crime.

In the next posts of the Forensic View, we will deal with each of these critically important perceptual and cognitive factors as they apply to the criminal justice system.


Fenici, R., & Brisinda, D. (2004, October). Cardiac and psycho-physiological reaction during police action and combat shooting. Society for Police and Criminal Psychology, Rome, Italy.

Sharps, M.J. (2002). Processing Under Pressure: Stress, Memory, and Decision-Making in Law Enforcement (3rd ed.). Flushing, NY: Looseleaf Law Publications.