The Brain Fills-In the Gaps

Editor’s Note:  This is the Second Article in our “Brain Principles” Series.


“I told them that my partner was standing behind me to my right when the incident went down. But when they pulled up the CCTV recording, he was way off to my left and in front of me. I felt so stupid. How could I not know where my partner was?” The officer told me. “I mean, it wasn’t critical to the investigation, but I felt like a liar, like I was hiding something. And even though I’ve now watched the incident and have seen for myself where my partner was standing, my memory is still that my partner was behind me and to my right.”

The incident – a man wielding a machete in a large public area, threatening to chop everyone into pieces – had happened several months prior; yet this responding officer describing the incident to me was obviously still disturbed by his false memory.

Has something similar happened to you? Have you had a memory during a critical incident that was challenged by a fellow officer or a citizen who then provided evidence that your memory was inaccurate? Having your memory proven wrong can not only be embarrassing, it can be troubling. Why does this happen?

Benefit: Allows Experiencing the World as One Single Event

To understand the current description of how an officer can form inaccurate memories during a critical incident, you first need to understand a few things about your brain. Your brain is an information processing machine. To boil it down to the basics, your brain is built to take in information from the environment, process it to make sense of things, and then take action based on that information. Perception and action go hand-in-hand. Without one, there would be no purpose for the other.

c2expert-logoFor our discussion here, let’s focus strictly on the perception side of the equation. Your brain uses your sensory systems to gather information from the environment. It uses your eyes to gather visual information, your ears for auditory information, your nose for olfactory information, etc. But the signal your senses receive is not always clear; the signal always contains noise[1] to some degree. For example, a person standing near you may cough in the middle of another person’s sentence, partly occluding the words. The inside of a building may be dimly lit, leaving you straining to see what is in the deep corner or under a table. There is noise in the signal. In the real world, where you operate, noise is always embedded in the signal.

When machines process information (signals), noise can disrupt their functioning resulting in failure. A loud sound or a flash of light masks a portion of the signal, disrupting processing in the machine. Even when it seems the noise is minimal, a machine can fail to function correctly. Here is a personal example: when making an electronic bank deposit on my phone, I often have to retake the pictures of the check multiple times because the lighting wasn’t just right or my hand wasn’t steady enough, or my phone wasn’t close enough. There was too much noise for the machine to handle.

Those types of disruptions don’t bother you in the same way they bother machines. Even when loud sounds and flashes of light are present, you can still gain an understanding of what is happening in your external world. Using knowledge from past experiences, your brain makes assumptions about the signal behind the noise. Your brain fills-in the gaps.

Because your brain is sophisticated enough to (usually) make accurate assumptions about the signal, you can process the signal while ignoring the noise. Instead of experiencing your world as a conglomerate of chunks of information, chopped up by the noise in your surroundings, and then later cobbled together through memory, you experience your world as one seamless event. Filling-in the gaps gives you a huge information processing advantage. Your brain is so good at doing this that you cannot even tell which parts of your experience were the actual signal and which parts were filled-in. The entire event seems natural, like it was all signal and no noise. Your brain is awesome!

Problem: Can Lead to Misperceptions and Inaccurate or False Memories

As long as the small details behind the noise are not important, filling-in the gaps is a win. But in your line of work, this isn’t always the case. The small details may be extremely important. Add to that the fact that there is almost always a great deal of “noise” in your world events. The situations you encounter on a regular basis are rich with auditory, visual, and olfactory noise embedded in the signal you are trying to process. Now add to that the possibility that “threat of harm” or “threat of life” is present in your events and the signal gets even more jammed up.

Let’s look specifically at how survival stress can influence this process. As your system starts to ramp up, the subconscious brain hijacks the conscious brain and robs it of resources in order to fuel the fight-or-flight system (among other things). Fewer resources in the conscious brain means a smaller portion of the signal is processed. The result often is tunnel-vision and auditory exclusion because there simply are not enough resources available for you to processes everything you are seeing and hearing. Imagine how much information needs to be “filled-in” under these circumstances.

I asked the officer in the above example if he was the contact or cover officer in this particular machete incident. “Contact” he said. Next, I asked him to tell me where his partner is usually positioned when offering cover. “He is usually behind me, to my right.”

So there you have it. His brain was filling-in the gaps. He expected his partner to be where he usually was, so his brain assumed his partner was behind him to the right. His brain was doing what it always does to help him out by filling-in the gaps.

In this example, there was no real harm. But if his partner’s positioning had been a critical element in this incident, his brain would have let him down. Remember that your brain is built and operates in a way that lets you experience your world as one seamless event; but a side effect of this type of processing is that your brain also keeps you from discerning what parts of your experience are signal and which parts are based on assumption. Both signal and assumptions are processed in the same manner in your brain. Thus, the officer’s assumption of where his partner was, became his memory of where his partner was.

Solution: Keep Stress and Distractions Low

The fact that the officer was wrong about where his partner was in relation to the event was not a big deal in this example, it had no real bearing on the case. But it was a big deal to the officer. Even after seeing video footage that contradicted his memory, his memory had not changed. He still remembered his partner being behind him to the right. That bothered him. A lot.

If the circumstances had been different and his partner’s positioning was a central concern in the event, the officer’s false memory would have huge ramifications. In your job, it is important for your recall of events to be accurate. You should realize when and under what circumstances your memory is more likely to be inaccurate so that you do not fall into a memory trap.

Here are two things that will help you in such situations: (1) understand that your brain is built to fill-in the gaps and does so without your permission or awareness; and (2) keep survival stress low to reduce noise and enhance signal processing.

Understand that your brain fills-in the gaps. Understanding that your brain fills-in the gaps, and does so without your awareness, forces you to rely less on your memory and instead look for other pieces of evidence to help you understand the event. Stating this for you to consider is the first step. You need to know how the brain works in order to devise a plan to help you solve the problem.

Next, you have to comprehend this concept by understanding how it fits into one of your past events. It’s one thing to hear about the brain filling-in the gap; identifying a time when your brain actually filled-in the gaps takes your understanding of this concept to a deeper level.

The final step is the most difficult and most crucial: you have to apply this knowledge in a future event. The reason the final step is so difficult is because it forces you to question your own memory. You have to allow pieces of information from an event that conflict with what you believe happened at the event to take precedence over your memory. That is an extremely difficult task. The officer in the above example continued to believe his memory of his partner’s positioned even after seeing CCTV evidence to the contrary. Memory is powerful. You must harness it ahead of time by realizing that it can fail.

Reducing stress enhances signal processing. Reducing survival stress is important for so many reasons; helping your brain build accurate memories is just one of them. In relation to our topic, reducing stress not only reduces the number and types of signal disruptions your brain is processing, it allows more of the signal to be processed in the first place. Remember, in order to fuel the fight-or-flight system, your subconscious brain robs the conscious brain of resources. The result is tunnel-vision, auditory exclusion, and a host of other related issues that often result in “vapor lock.” These symptoms all cause a reduction in signal processing.

There are many ways to reduce the effects of survival stress. Two of the most effective methods are to use tactical breathing and to slow the event down in your head so that you can preplan and take action rather than just react.

  • Tactical breathing indirectly controls heart rate so that beats per minute stay within a safe range. Breathing is a powerful tool. Slow, deep breaths supply large amounts of blood and oxygen to the brain. This is the fuel the conscious brain needs to function properly.
  • Slowing an event down is something that takes more practice. It means getting into the habit of thinking and preplanning even before an event starts to go wrong. It is sometimes referred to as mental preparedness or having the proper mental mindset. Find a program that works for you and build those tactical habits.

The fact that your brain fills-in the gaps gives you a huge advantage when it comes to processing information and understanding your world. But in your career as a law enforcement officer, it can cause problems. Be aware that your brain fills-in the gaps and reduce stress to help it function as it should.

Until the next article in the Brain Principles series, stay safe and professional.


[1] Noise in this context refers to an unwanted disturbance in the signal. Noise can be in the auditory system, like we usually think of it, but there can be visual noise and unwanted disturbances (noise) in the other sensory systems as well. Noise simply means that the processing of environmental information was disrupted in some way.

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