Auditory exclusion
The call I was dispatched to was a delayed kidnapping call. Now I know, some of you reading this are thinking: “What child was taken? Was there an amber alert issued?” No, it wasn’t that type of kidnapping. As the statute states, kidnapping occurs when a person is removed from some place without their consent with intent to terrorize that person. My partner and I met with the victim, he stated that he was surrounded at a nearby gas station by several vehicles. He told us someone removed him from his vehicle, threatened him, and forced him into a nearby vehicle without his consent. After listening to the victim’s story my partner and I both concluded that we had charges of kidnapping.
We drove to the suspect’s house and knocked on the door. A female suspect came to the door, and after a brief conversation, she admitted she was at the nearby gas station when the events occurred. My partner advised her she was under arrest. As he did this, she tried to run back into the house. So, my partner apprehended her. As he grabbed her by the arm, unbeknownst to me a large German Shepherd came from behind her and bit my partner on the top of his thigh. I heard my partner scream, and the pain immediately took him out of the fight.
I backed up and drew my service weapon. The German Shepherd lunged at me with its large jaw wide open and teeth showing. Bang! Bang! I was able to get two shots off while stepping backwards to prevent me from getting bit. The only focus I had at that moment was a giant dog coming at me. I had complete tunnel vision. The German Shepherd lay dead on the driveway. I felt awful. It felt like my heart was going to pound out of my chest. This was the first time I had ever drawn my service weapon and deployed it in the line of duty. I was wondering why I had not heard either of the shots fired. I now know I was experiencing auditory exclusion.
Most police officers are aware of tunneled vision because they were taught about it in their basic police academy program or perhaps in a medical training program. Auditory exclusion (a form of tunneled hearing) is far less known, but every bit as dangerous.
There have been multiple research studies conducted on the impact of stress on hearing over the past 20 years. Most have been done with the military and some have been done with law enforcement.
Functional magnetic resonance imaging (fMRI) scans allow researchers to peer inside the brain, non-evasively, to see how the brain is functioning during the process of thinking and making decisions. Some pretty cool things have resulted from this technology. One lesson has been our understanding that the conscious brain is a horrible multitasker. (NOTE: The subconscious brain, on the other hand, is a wonderful multitasker.) Unfortunately, we process what we see and hear (mostly) with our conscious brains. This means the visual processor and the audible processor often share resources or, in some cases, one sensory processor can overtake the other, resulting in the overtaken sense to shut down.
In the presence of high-stress visual stimulation, the processing of audible information may be dulled or it may be turned off completely! Hence the word exclusion. If the audible processor is still functioning but its acuity is turned down, the person may describe the sounds they hear as muffled or distant. For reference, it sounds like mumbling.
The eardrums
During a high stress event the ears are working just fine… sort of. Physically, all the right parts are moving and taking in the sound waves, but something can happen to diminish the processing of the sounds into meaningful information.
Complicating the problem of competing sensory processors, once a person’s heart rate exceeds 175 beats per minute, hearing can diminish. Research has revealed the blood rushing through the eardrums at high speeds actually creates noise that can muffle incoming sound waves. That noise may come off as static, pulsing, a hiss, or ringing in the ears.
As police officers working under stress, do we ever experience heart rates above 175? You know we do. In fact, when I shot that German Shepherd, I know my heart rate was through the roof. I watched the video recorded from my dash cam and I could hear my voice escalating. If your hearing is diminished due to a rapid heart rate, there is nothing you can do to rectify the situation other than lower the heart rate. You can’t squint with your ears.
TIP: One of the best ways to lower stress-induced tachycardia is to use a controlled breathing technique called tactical breathing. Simply breath in on a four count. Hold your breath for a four count. Breath out on a four count. Stop breathing for a four count. Repeat this several times.
Tune it out
The brain, in an effort to help you make sense of what is happening in a high-stress, high-consequence situation, can also filter out the sounds your brain determines to be unimportant (i.e., those sounds the brain perceives to be “noise”). Sometimes this can be helpful. Other times it can be devastating. While full of Darwinian good intentions, the brain could, inadvertently, filter out the sounds of the very thing that could harm you.
Sensory integration
What happens when the brain tries to sort out conflicting information? In other words, what the eyes are seeing and what the ears are hearing do not align (non-congruent). In this case the brain does its darnedest to make it all fit together in a coherent way. If you’ve ever been to a movie theater, you’ve experienced sensory integration.
In the movie theater the speakers are not behind the screen. They are on the walls. When someone on the screen is talking, the speaker is not where their mouth is. Yet it appears as though the sounds are coming out of their mouth. This is because the brain takes the cues from the eyes and the cues from the ears and integrates them, or fits them together in a way you’ll understand and gives you the appearance the sounds are coming from the mouth on the screen… which they aren’t.
Vision trumps all other senses
When there is a conflict between what the ears are hearing and what the eyes are seeing, vision will most often be the winner. This is why the sounds appear to be coming from the star on the movie screen, even though they’re not. A very simple, albeit perhaps juvenile, exercise can be used to test this phenomenon on an unsuspecting person. Tell the person to “Touch your finger to your nose” while actually touching your finger to your ear. Chances are very good they’re going to touch their ear, despite your verbal instruction to touch their nose. The brain takes its instructions from the eyes, not the ears.
On an emergency scene this can have some critical implications. For example, if you hear one thing on the radio yet see something else with your eyes, there’s a risk that in the process of sensory integration, your visual cortex wins and what you see is what is processed. The audible message, in turn, loses (is changed, distorted, or may be tuned out). It’s almost like the visual image convinces the brain to disregard the audible message because it doesn’t make sense. As you can imagine, this can wreak havoc on your ability to develop and maintain situational awareness.
