Stress & Memory: Important New Findings From FSRC Research

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Final analysis of data gathered by the Force Science Research Center during a simulated shooting experiment has revealed important new findings about officers’ perceptions and recall that could bear significantly on OIS investigations.

Among other things, the testing showed that:

  • Officers tended to recount vastly more information about what happened when interviewed by investigators than when told to write a report;
  • Written reports, although much briefer, were more factual than accounts given in interviews;
  • The error rate was considerably lower among officers who were allowed to confer briefly before being questioned;
  • Whether expressed orally or in writing, what officers were able to accurately remember about the confrontation was severely limited in scope by their inescapable compulsion to focus narrowly on the threat they encountered.

“This is one of the most significant studies ever done in law enforcement regarding attention, memory, and memory-mining procedures,” FSRC’s executive director Dr. Bill Lewinski told Force Science News.

“It has important implications for officers who survive gunfights, and particularly for the investigators, review boards, prosecutors, attorneys, judges, and juries who examine and assess their actions after the smoke clears.”

The experiment exposed 46 experienced officer volunteers from armed units of the London Metropolitan Police to a sudden confrontation with a shotgun-wielding “hostage-taker” at a training facility in England. After resolving the encounter, each officer provided an account of what had happened, either in writing or during individual interviews with I.A. investigators.

The data was gathered at the end of 2006 and since then has been meticulously analyzed by FSRC’s research team, headed by Lewinski. An extensive, detailed report of their findings will appear in the January 2009 issue of the professionally peer-reviewed quarterly journal Law Enforcement Executive Forum.


In teams of 2 or 3, the officers (all of constable rank and all but 3 of them male) were sent to a location in the training center that had been stage-set as a hospital reception lobby, complete with staff and “waiting patients.” They were told to proceed to a “locked ward” upstairs to guard a wounded armed robbery suspect.

As each team walked toward a stairway, a “brother” of the suspect who wanted to visit him became unruly at the reception desk, shouting, swearing, and physically threatening the receptionist. As intended, the officers invariably became involved in this conflict.

As they attempted to defuse the brother’s agitation, a door to the left of the desk flew open and a role-player portraying a hostage-taker burst into the lobby, his left arm around his hostage and his right hand clutching a double-barreled shotgun. He squeezed off 2 Simunition blanks toward the floor, disengaged from the hostage, and pointed the gun at the officers. They reacted immediately to defend themselves with their Simunition-loaded Glock 17s.


Once the encounter was resolved, the involved officers were channeled into 1 of 4 reporting options. With instructions to recount as fully as possible “everything that happened,” they were assigned to handwrite reports after conferring with their teammates about the incident for up to 20 minutes, to write without conferring, or to be interviewed after conferring or not conferring.

Since the conclusion of the testing, members of the research team have compiled a tedious but critical collation at FSRC’s headquarters at Minnesota State University-Mankato. They have compared typed transcriptions of the officers’ written reports and interview statements to videotapes from 3 cameras that ran throughout the experiment. The cameras, positioned to record the action from different angles, documented frame by frame what actually did occur.

Results of this analysis, Lewinski says, is in some aspects “astounding.”


First, apart from any issues of accurate recall, the researchers “indisputably” confirmed that officers in a violent, rapidly unfolding, seemingly life-threatening situation inevitably experience what is popularly called tunnel vision or tunnel hearing, Lewinski asserts. He prefers the term “selective attention.” Either way, it translates into a sharply narrowed field of sensory concentration, in which elements of the scene that do not relate directly to an officer’s survival are effectively screened out by his or her brain.

“It is obvious that the constables could not see everything occurring at any instant in this encounter, but the items [they] remembered at the end of the incident are a good indicator of their focus of attention during the incident,” Lewinski notes in the Forum report.

The average officer in the experiment was 4 times more likely to remember “external” elements associated with the threat (the type of weapon presented, the suspect’s behavior, etc.) than “internal” elements (such as an awareness of his/her own thoughts and physical behavior). The more closely the “external” elements were related to the threat being presented the more likely they were to be recalled.

“This narrow focus allowed the threatened officers to concentrate on what was important to them at the time–assessing and reacting to the suspect,” Lewinski explains. “This appeared to greatly facilitate their performance and effectiveness.”

But unfortunately, this narrow focus simultaneously caused them to “miss other items about the scene that may later turn out to be important, and impaired their ability to provide full and complete reports about the incident. Because an officer doesn’t focus on a certain element in the midst of fighting to save his life doesn’t mean that some investigator won’t focus on it later.” For example, Lewinski notes, “every constable who could see the shotgun usually reported a quite detailed and accurate description of it. They tended to be accurate about the shooter’s actions, as well.

“But they were less accurate about the suspect’s clothing and were often quite unobservant or inaccurate about the hostage. They almost never noted the behavior of anyone other than the shooter, including the location or action of his ‘brother’ and even other constables. They were often unaware, for example, of the number of rounds their partners fired.

“In short, they were ‘attentionally blind’ to anything on which they were not focused.”

This phenomenon is something investigators and reviewers of an OIS need to keep in mind, Lewinski stresses. “An officer who says he can’t remember extensive, broad details of a shooting is not necessarily being deceptive or evasive. Memories of these fast, intense events may be quite limited because the officer’s focus is uncontrollably limited during their occurrence, and human beings simply can’t remember what they have not noticed or paid attention to.”


The officers in the experiment who wrote reports about what happened “provided the least amount of information, despite being requested to write full and complete reports about everything in the incident,” Lewinski reports.

“They reported on the essence, providing little extra information. Their descriptions of the incident and the subjects were the barest, with little or no elaboration on such things as behavior or clothing. Their reports on their thought processes during the incident were also extremely sparse.”

Whether they were allowed to confer with their teammates before writing did not appear to make a difference in the extent of descriptions they provided. “What they reported was still sparse,” Lewinski says. “They seemed to concentrate only on the narrowest elements related to the legality of their actions.”

By contrast, officers who were interviewed “provided much more information overall”–generally 2 to 4 times more than the report-writing groups. Although, like the writers, the interviewees still focused predominately on “external,” threat-related items, they were notably more voluble about their own thoughts and behavior–aspects of shootings that courts and review boards often tend to be concerned about.

Again, whether interviewees conferred or did not confer before giving their statements did not seem to affect the volume of information they provided.


The number of items officers in the experiment incorrectly reported on “is truly astounding and definitely needs to be investigated further,” Lewinski says.

The lowest rate of errors in the officers’ memories occurred among those who wrote reports. “The average number of errors for each constable in this category was somewhat less than half of one error per incident per constable,” Lewinski reports.

Officers who were interviewed, on the other hand, had error rates that were “very high,” averaging more than 5 mistaken memories apiece in their accounts of what happened.

The fact that the report writers as a whole volunteered less information meant that they had “less chance of being mistaken,” Lewinski concedes. But this “cannot be the only reason” for the difference, which he calls “very significant.”

Most of the errors occurred regarding elements on the periphery of the officers’ attention–items and behaviors on the fringes of or actually beyond the officers’ ability to perceive them. Lewinski says it appears that interviewers pressed for more information about these things than the officers could truly produce from memory and in an effort to answer the questions, they innocently filled in the gaps with guesses or surmises that proved to be inaccurate.

“This is a well-known phenomenon in memory research,” Lewinski says.

[To read more on this, visit the “articles” section at www.forcescience.org or simply click here for a direct link to an important article by Dr. Bill Lewinski and Dr. Audrey Honig]

Apart from this study, he observes, errors tend to increase when interviewers frequently interrupt officers with questions rather than allowing them to recount what they remembered in an unbroken narrative reconstruction before posing follow-up inquiries.


A finding that Lewinski describes as “astounding” was the significant positive effect that conferring among teammates had on the error rate.

Team members who took a few moments to discuss what happened before they then wrote a report of their experience committed the fewest memory errors of all. This group of 14 constables provided a total of 314 correct details about what they had been narrowly focused on during the action. They recorded only 2 factual errors in all that data. “An amazing statistic,” Lewinski says.

The error rate among officers who wrote reports without conferring, while still extremely low, was more than 4 times higher, by comparison–plus, they remembered fewer items, on average.

Among interviewees, those who conferred before being questioned “were considerably more accurate in reporting those items and behaviors that they were narrowly focused on than the constables who did not confer and were interviewed.” Specifically, conferring resulted in about 25% fewer errors among the interviewees, Lewinski says.

The greatest differential occurred between the test subjects who wrote reports after conferring and those who were interviewed without conferring. “The error rate for those who did not confer and were interviewed is 47 times that of those who conferred and wrote reports,” Lewinski says.

In the forthcoming Forum article, Lewinski says that while statistical analysis indicates this finding is reliable, he is “still suspicious” of it because of the relatively small sample size in one of the experimental groups and wants to investigate it further.

It’s interesting to note that with the exception of one officer, those involved in the groups that conferred said they did not learn “new” information about the incident during their discussions. Rather, it seemed, latent memories they had of the incident were “refreshed” and brought to the surface by the conferencing.

“In the United States,” Lewinski points out, “there is a stigma attached to officers conferring about a force situation. It tends to be equated with them inappropriately ‘getting their stories straight,’ concocting ‘facts,’ or skewing the circumstances to serve their best interest.

“In England, on the other hand, officers routinely confer before writing major use-of-force reports, just as partners confer before writing reports of other criminal activities by suspects.

“This experiment, where the officers had little or nothing to gain by lying, strongly suggests that conferring should be regarded as a legitimate component of eliciting the richest, most complete, and most accurate memories that an officer can bring to a shooting investigation.”


To learn more about the focus of attention and how best to evoke accurate memories of a violent encounter, FSRC will be part of a major new study in January, involving more than 300 officers from a variety of agencies and headed by Dr. Lorraine Hope, a psychologist with Portsmouth University in England.

The officers will respond to a simulated incident in progress involving firearms, and then produce a written account of what happened. Some will be allowed to confer with partners before writing, others will not.

In addition to the officers immediately involved, the complex incident will be witnessed by inner-city residents bused to the location and by other officers not engaged in the action.

Part of this experiment will involve testing a new “guided-response” report-writing format developed by psychologists Dr. Fiona Gabbert of the University of Abertay in Scotland and Dr. Ronald Fisher of Florida International University.

As with the hostage-taking scenario, this new study will be funded by the London Metropolitan Police Federation and the London Metropolitan Police Dept. In all, experts from 5 universities will be involved.

Force Science News will report on findings as soon as they become available.

NOTE: After publication in Law Enforcement Executive Forum, a full report on the hostage-taking experiment by Dr. Lewinski, titled “The Attention Study: A Study on the Presence of Selective Attention in Firearms Officers,” will be posted on the Force Science Web site.

You can also see an earlier article by Force Science News about a secondary aspect of this research, the effect that the high-stress scenario and the recounting of it afterward had on the involved officers’ heart rate. Significantly, researchers discovered that being interviewed about their experience was nearly as stressful for the officers as the confrontation itself. See FSN [12/15/06], “New Findings About Simulation Training and the Stress of Post-Shooting Interviews.”

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