A Survey of the Research on Human Factors Related to Lethal Force Encounters

A Survey of Research on Human Factors Related to Lethal Force Encounters

Introduction

• To effectively train and evaluate officers, understanding brain function in tactical environments is crucial.
• The article explores routine information processing, the impact of stress on perception, common perceptual distortions, and their effect on reaction time.
• Training recommendations are provided to reduce errors and response lag.
• Improved methods for memory recall are offered to increase accuracy.
• The information is presented objectively.

The Human Mind and Information Processing

• Understanding how the mind works is essential to explaining human behavior.
• Information is processed from both internal (thoughts and feelings) and external sources (senses).
• Perception and memory are active processes, influenced by schemas and expectations.
• Schemas and expectations can distort perception and recollection of critical incidents.
• Perception is reality due to the strong influence of schemas.
• Traumatic incidents lead to perceptual distortion and memory impairment, with greater stress leading to greater impairment (Grossman & Siddle, 2005).
• Witnesses of the same event can have different perceptions (Loftus, 1979).
• Stress and distractions experienced by law enforcement personnel in tactical situations amplify perceptual distortion (Morgan, 2004).

Types of Errors Related to Perception

• Two types of errors affect perception, performance, and memory:
  • Type I errors (false negatives): Rejecting something that should have been accepted (e.g., failing to identify a suspect with a firearm).
  • Type II errors (false positives): Incorrectly perceiving something (e.g., an officer incorrectly perceiving a suspect has a gun).

Error Rates

*   Typical false negative rate for officers in high-stress situations is approximately 4% (Lewinski & Hudson, 2003).
*   False positive rate averages 9% in laboratory research (Lewinski & Hudson, 2003).
*   Simulation testing indicates Type II errors may be as high as 30-40+% depending on department training and experience (Aveni et al.).

• Both types of errors are inevitable and inversely related.

Lessons Learned (Pages 1-2)

• Perceptions and recollections are colored by prior expectations.
• Greater trauma generally increases the risk of perceptual distortion and memory impairment.
• Reducing false negatives automatically increases false positives, and vice versa.

The Science of the Mind

Memory Components

• Three critical components of memory: receive, retain, and recall.
• Attention is the primary process determining what we receive, retain, and recall.
• The brain has a limited capacity to observe and selects what to attend to.
• Selection is generally survival-based.
• Information cannot be simultaneously attended to and processed from multiple sources or competing senses (Lewinski & Hudson, 2003; Shomstein & Yantis, 2004; Strayer, Drews & Johnston, 2003).
• Focusing on a visual cue reduces the ability to attend to other visual or auditory stimuli.
• We can see either the forest or the trees, but not both at the same time.
• This is related to figure-ground perception.

Figure-Ground Perception

• In law enforcement, officers cannot perceive two equally significant elements at the same time.
• Training and experience enhance visual or auditory attention and acuity.
• Experienced officers pay varying levels of attention based on the situation and the importance of cues to survival (Hsieh, 2002; Shomstein & Yantis, 2004).
• This is referred to as tunneling or selective attention.
• Selective attention can cause the brain to ignore or suppress other important information.
• Selective attention explains how an officer can miss something in their field of vision or range of sound (Rumar, 1990; Simons, 2003; Strayer et al., 2003; Strayer & Johnston, 2001; Summala, Pasanen, Räsännen, & Sievänen, 1996).

Selective Attention Example

• Explains how someone listening to the radio while driving can be unaware of the broadcast content (Brown, Tickner & Simmonds, 1969; McCarley et al., 2001).
• Selective attention is magnified under high-stress conditions.
• Intense stress affects what an officer remembers and how they remember it (Grossman & Siddle, 2004; Lewinski, 2002; Morgan, 2004; Welford, 1980).
• Information deemed unrelated to the threat will have a low rate of recall.
• Officers will fixate on some element of the incident, resulting in a vivid memory for that aspect while limiting recollection of other facts (Bacon, 1974; Hockey, 1970; Mandler, 1982).

Recognition vs. Recall

• Information is more readily recognized than recalled (Morgan, 2004).
• Recognition involves comparing new information to old information.
• Recall requires recreating the memory from scratch.
• Recall memory is less subject to contamination.
• When investigating an incident, officers should first ask for a basic narration of the incident with as much detail as possible (recall), followed by specific queries or comparisons (recognition).
• One type of memory can stimulate another.
• A walk-through can stimulate recognition memory, which then facilitates recall memory and provides a more accurate report.

Information Retention

• Not all observed information is retained.
• The brain has limited capacity to retain or store information.
• The brain utilizes temporary and permanent storage areas.
• Short-term memory is reserved for immediately relevant information with no long-term utility.
• This storage area has limited capacity, averaging seven items.
• Recall is limited to approximately 30 seconds without reinforcement.
• The next level of short-term memory is for information deemed slightly more relevant but not significant enough for long-term memory.
• These memories fade over time, affected by factors like repetition, significance, and relevance to existing memories.
• Long-term memories take longer to acquire and are retained for life.
• Long-term memories may be hard-wired in the brain.
• Long-term memories include experiences, training, and education, involving information with attached meaning and/or emotion.
• The problem with long-term memory is accessibility, not capacity.
• Most processing occurs automatically at a subconscious level, though conscious interventions can impact the result.
• Connecting current information to previously learned information enhances recall.
• Strong emotion increases memory for specific details but may reduce the capacity to recall competing information.

Lessons Learned (Pages 3-5)

• The three "Rs" of memory are receive, retain, and recall.
• The brain can attend to only one source of information at a time.
• Not all information is perceived and/or retained for later recall.
• Strong emotion increases memory for specific details at the expense of recall for competing information.
• Comparison or recognition tasks can enhance memory recall.
• Basic narration of an incident should be the first step in any investigative interview since recall is less susceptible to contamination than techniques that involve specific queries or comparisons.
• Memories are just as likely to be inaccurate as accurate. Confidence in the accuracy of recall is not a reliable determiner of actual accuracy.

The Effect of Stress on Perception and Memory

• Physiological arousal from stress interferes with perception and memory (Broadbent, 1971; Horowitz, 1976; Janis & Mann, 1977; Morgan, 2004; Welford, 1980).
• This results from chemical reactions due to adrenaline and other hormones.
• The fight, flight, or freeze response produces both positive and negative effects on perception and performance.
• The survival stress response results in increased adrenaline and hydrocortisone, leading to:
  • increased heart rate
  • blood pressure
  • breathing rate
  • pupil size
  • perspiration
  • muscle tension.
• This improves blood flow to the brain, heart, and large muscles.
• Fine motor skills deteriorate as resources are allocated to gross motor facilities.
• The eye and brain work together to help us pay attention to important information.
• At low stress, the mind maintains a soft attentional focus across many senses.
• As stress increases, the brain narrows focus and excludes information deemed not important (McCarley, et al., 2001; Strayer et al., 2003).
• Attention focuses on expected hazards at the expense of awareness toward less likely hazards (Rumar, 1990; Summala et al., 1996).
• The more complex the environment, the more pronounced the effect of stress on perception and memory (Langham, Hole, Edwards, & O'Neil, 2002; Strayer et al., 2003).
• Response time slows in complex circumstances (Broadbent, 1971; Miller & Low, 2001; Welford, 1980).
• High levels of physiological arousal lead to inattentional blindness.
• Inattentional blindness is a failure to see what is directly in the line of vision due to attentional focus on a competing visual input.
• This results in unconscious rejection of information (Strayer et al., 2003; Strayer & Johnston, 2001).
• This is illustrated by figure-ground perception or selective attention.
• Auditory exclusion or selective attention also occurs with increased stress, focusing on the perceived threat.
• Information not relevant to the primary task is filtered out.
• An example is a mother recognizing her child's voice in a crowd.
• The process of selection and attention occurs in the brain, not in the senses.
• The brain selects what it needs and actively rejects the rest, failing to create a durable memory of rejected information (Rumar, 1990; Strayer et al., 2003).
• Selection is determined by survival priorities or the importance of the information.
• Peripheral information is more likely to suffer from selective attention.
• An officer in a high-stress situation can be looking directly at something and be blind to it (Simons, 2003).
• This selective attention can occur across all senses (Simons & Chabris, 1999).
• An officer's perceptions and memories are influenced more by what their attention is focused on than by what actually passes before the senses.
• When confronted with a life-threatening incident, the body prepares to physically respond.
• This involves sympathetic stress reactions: fight, flight, or freeze.
• All stress response system resources are allocated to survival.
• Increased blood flow to the heart and large muscles prepares the body for physical response.
• The brain narrows perception and attention to focus on the life-threatening event.
• The brain changes the way it processes information and makes decisions.
• Two demanding tasks cannot be equally shared (Alm & Nilsson, 1995; Briem & Hedman, 1995; Hsieh, 2002).
• People switch between tasks rather than doing them simultaneously.
• Cognition and critical decision-making under high stress are typically the least practiced skills for officers.
• The officer's ability to accurately perceive and process information in a high-stress situation is, therefore, further impaired through this lack of practice.
• Under high stress, the brain shifts from thinking to reacting.
• The focus shifts from the new brain and hippocampus to the amygdala (old brain).
• The adrenaline surge results in increased cortisol, decreased hippocampus functioning, and increased amygdala functioning, improving the speed of survival response (McGaugh, 1990).
• The hippocampus and other higher-level brain processes (thinking brain) begin to shut down (McGaugh, 1990).
• The survival system focuses all its resources on responding, reducing cognition or conscious thought.
• Reactions are enhanced, but decision-making speed and ability are reduced.
• Cognitive processing deteriorates.
• Learning and memory become less of a priority (Squire, 1986).
• These higher brain functions, while having the potential to increase the accuracy and appropriateness of the response (Schweitzer, 2001), also tend to slow the response.

Lessons Learned (Pages 6-8)

• When stress levels are low, the mind maintains a soft focus across the senses as well as on internal thoughts and feelings.
• Failure to perceive what would otherwise appear to be obvious is caused by inattentional blindness and auditory exclusion.
• Physiological arousal interferes with perception and memory at all levels, including the ability to receive, retain, and recall information, particularly for information deemed "unimportant."
• The system is predisposed to focus all of its resources on responding to the detriment of conscious thought.
• The ability to accurately perceive and process information is a perishable skill.
• The ability to turn off the adrenaline response is critical to maintaining conscious thought and control.
• Emotion activates the amygdala or old brain, increasing recall of central details at the expense of peripheral details.

Common Perceptual and Informational