Force Science News #213:

When you don’t see what’s visible: The inattentional blindness factor & more

FS training note: Congratulations to the graduates of our most recent Force Science Certification Course conducted last week in Alexandria, VA. They proudly represented 34 agencies from four countries and 19 states and provinces. Once again it was an honor to work with such an impressive group of professionals who we’re proud to welcome to the ranks of Certified Force Science Analysts!


A special thanks to the outstanding staff at the Department of Homeland Security’s Consolidated Training Center and to the Center’s former Division Director and current Project Manager for the U.S. Dept. of State’s Diplomatic Security Division, Ron Libby, who is also a Certified Force Science Analyst. We were honored that Ron, a Certified Force Science Analyst, made a guest appearance and shared a motivating opening presentation that set the pace for this excellent group.


[Click here for the upcoming Force Science Certification Course schedule or visit]


In this edition:


I. When you don’t see what’s visible: The inattentional blindness factor


II. Research findings mark the dismal toll of police stress


III. Coming to courtroom near you: more brain scans of violent suspects





I. When you don’t see what’s visible: The inattentional blindness factor


Experiments mirroring a real-world case that resulted in an officer going to prison for perjury have confirmed that a trick of the mind called inattentional blindness—the failure to see something important that is clearly within your field of view—can occur under stressful circumstances on the street.


The officer’s conviction was described in detail in a book called The Invisible Gorilla, which Force Science News reviewed in Transmission #160 [10/8/10. Click here to read it]. He’d been in foot pursuit of a shooting suspect at 0200 in Boston and had run past three fellow officers who were brutally beating a black male. In a public furor that arose over the beating, the officer insisted he didn’t see the incident even though he ran right past it.


Investigators, prosecutors, and a jury figured he was lying in a classic case of “blue silence” and he was sentenced to 34 months behind bars. They assumed that because he could easily have seen the beating, he must have seen it.


Authors of the book, behavioral scientists Dr. Christopher Chabris of Union College in Schenectady, NY, and Dr. Daniel Simons of the University of Illinois-Champaign, argue that the officer could have experienced inattentional blindness, which occurs when you are so intently focused on a particular subject or task that your mind, without your realizing it, automatically screens out other, unrelated stimuli.


There is a “common but mistaken belief,” the authors explain, “that people pay attention to, and notice, more of their visual world than they actually do.” (What the researchers call “the illusion of attention” is explored from the perspective of investigating officer-involved shootings in the certification course on Force Science Analysis.)


Inattentional blindness has been well documented in laboratory experiments, but some months ago Chabris and a research team that included Simons decided to test it on the street in conditions similar to what the Boston officer had experienced.


First they asked 20 college students one by one to pursue a male confederate for about three minutes while he jogged for about three minutes along a 1,300-ft. route at night in an area lit with streetlamps. While running about 30 ft. behind, each participant was to count the number of times the runner touched his head with either his left or right hand—“a task that required focused attention.”


About a third of the way into the chase, in a driveway just off the path, three volunteers staged a fight in which two of them beat the third. These subjects “shouted, grunted, and coughed,” the researchers report—and were visible to each pursuing runner for at least 15 seconds before the chaser passed by.


At the end of the route, the researchers asked the subjects how many head-touches they had counted. “Then we asked whether [they] had seen anything unusual along the route and then whether they had seen anyone fighting,” the researchers write. Only seven out of 20 (35%) had seen the brawl.


To check if darkness had affected visibility, the team repeated the experiment in daytime with 16 fresh pursuers. Even though in this test the simulated beating was visible for at least 30 seconds (twice as long as at night), 44% of the subjects failed to notice it.


Finally, in a third iteration of the scenario 58 new pursuers were assigned by coin flip either to keep separate counts of head touches by the runner’s left and right hands during a daylight run or just to follow the runner without counting. “One hallmark of inattentional blindness is that increasing the effort required by the primary task decreases noticing of unexpected events,” the researchers explain.


Sure enough, 58% those with the so-called “high-load condition” of needing to count touches did not see the fight, while 28% of those only chasing (in “no-load condition”) failed to do so.


Across the three experiments “with 94 total participants,” the research team writes, “a substantial number of subjects failed to notice a three-person fight as they ran past it…both at night and during the day….” Dr. Bill Lewinski, executive director of the Force Science Institute, who was not involved in these experiments, observes:


“If the stress involved in merely counting head touches provokes this level of inattentional blindness in ordinary people, just imagine how extensive the phenomenon can be when police officers are intently focused on a threat to their lives or on taking custody of a deadly suspect, where the stakes are tremendously higher.


“Investigators, force reviewers, and jurors need to be educated that the mind can play many tricks under stress and that surprising gaps in observation and memory are not necessarily evidence of evasion or deceit.”


He points out that the results of the Chabris team’s experiments are consistent with findings by Force Science who with researchers from the United Kingdom tested the effect of cognitive work load on attention and perception as part of a ground-breaking 2010 study of officer performance when exhausted.


“After they were thoroughly stressed,” Lewinski explains, “officers were sent into an incident in a room where they were confronted by a very aggressive and hostile assailant who was within reach of a number of dangerous weapons, including an assault rifle, sawed off shotgun, handgun and knife. Most of the officers saw only one of the weapons, even though they were all within reach and constituted potential threats to their lives in that scenario. Shortly after, only 27% of the stressed officers could correctly identify the assailant from a photo line up whereas 54% of the non-exerted officers correctly identified the assailant.


It is very clear that officers in the midst of a dynamic encounter tend to see far less than what the public believes they should.


For free access to the full report on the Chabris team’s experiments, click here.




II. Research findings mark the dismal toll of police stress


“Policing,” writes Dr. John Violanti, one of the leading researchers of law enforcement stress, “is psychologically stressful work filled with danger, high demands, ambiguity in encounters, human misery, and exposure to death.”


And that may be the least of its dark side.


“Law enforcement is one of a number of often stressful professions that has attracted the interest of researchers who are compelled to study the stressors involved in a particular line of work and their impact on those engaged in the profession,” says Dr. Bill Lewinski, Executive Director of the Force Science Institute. “For a significant number of cops, the worst part of the job will likely be its long-term negative impact on personal health and wellbeing, ranging from heart problems to cancer to suicide as identified in recent research.”


The dismal truth is pulled together in a recent special issue of the International Journal of Emergency Mental Health, which devotes its pages to seven major reports on the adverse health outcomes linked to common daily stressors in police work. The findings are drawn in large part from a multi-year study led by Violanti, a former NY State trooper, involving a vast and diverse pool of Buffalo (NY) PD officers.


Violanti is a professor of social and preventive medicine at the University of Buffalo School of Public Health and Health Professions. His landmark exploration of stress outcomes was funded by the National Institute for Occupational Safety and Health.


A summary of the Journal articles can be accessed free of charge at the NIOSH blog. Click here to visit the site. Within the blog, you can link to abstracts of the various studies.


It’s not happy reading. Among the highlights:


• Striking differences between cops and the general population are found in multiple important health-related categories. Officers are nearly twice as likely as civilians to suffer symptoms of depression (12% vs. 6.8%), significantly more show evidence of the metabolic syndrome believed to increase the risk of cardiovascular disease and diabetes (25% vs. 18.7%), and nearly four times more likely to sleep less than six hours out of every 24 (31.4% vs. 8%).


• Sleep problems deepen as stressful feelings intensify. Male officers who perceive themselves having the highest stress levels are nearly six times more likely to get poor and inadequate sleep than the least stressed officers; females nearly four times more likely. Poor sleep adversely affects “emotional regulation,” and as sleep quality deteriorates depression symptoms escalate significantly among both male and female officers.


• In-depth examinations of obesity and of the metabolic syndrome reveal an association between obesity and depression in male officers and a link between stress and metabolic symptoms in female officers. Females seemed particularly susceptible to stress from “administrative and organizational pressure and lack of support.”


• Although retired officers are often considered to be at greatest risk for suicide, Violanti’s work suggests otherwise. After a 55-year retrospective of more than 3,200 officers, he reports that suicide rates are 8.4 times higher in working officers, compared to retired officers or those who left law enforcement.


• Another study, covering more than 2,200 officers across a 30-year period, concentrates on cancer rates. Officers seem similar to the US general white-male population regarding cancer overall. But they display an elevated risk of Hodgkin’s lymphoma, a cancer that can spread throughout the body via lymph nodes. And, Violanti writes, “The risk of brain cancer [among officers], although only slightly elevated relative to the general population, [is] significantly increased with 30 years or more of police service.”


The culture of police work, Violanti believes, often goes against improving stress-related health problems.


“The police culture doesn’t look favorably on people who have problems,” he says. “Not only are you supposed to be superhuman if you’re an officer, but you fear asking for help.” Officers who reveal that they suffer from a chronic disease or health deficiency may lose financial status, professional reputation, or both, he explains.


The solution, he suggests, needs to start at the academy level, with training that helps new officers understand signs of stress and how to get them treated. Education is also necessary for police leadership and management to accept officers who ask for help for their health issues.


Meanwhile, Violanti has more research underway.


Note: Violanti is scheduled to speak at a two-day conference on law enforcement suicide prevention Nov. 7-8 at the NY State Police Academy in Albany. Free, online registration is available at:




III. Coming to courtroom near you: more brain scans of violent suspects


Lawyers defending violent offenders may be more likely to try to introduce brain science into their cases after research recently reported from the University of Utah.


In what the NY Times calls “the most rigorous study to date of how behavioral biology can sway judicial decisions,” three researchers from Salt Lake City asked 181 state trial judges from across the US to read a hypothetical case (based on an actual crime) of a psychopath who was convicted of beating a restaurant manager senseless with the butt of a gun during a robbery attempt and leaving him with permanent brain damage. The defendant had a history of committing aggressive acts “without showing empathy.”


Half the judges in the experiment received a transcript of testimony from a “neurobiologist and renowned expert on the causes of psychopathy.” This expert witness, while agreeing that the defendant was a psychopath, stated that the offender had inherited a gene linked to violent aggressive behavior and described how the gene “altered the development of brain areas that generate and manage emotion.”


Judges who read this testimony as part of their case files decided, on average, that the offender deserved a sentence of 13 years—a full year less than the average sentence pronounced by judges who did not see this testimony. The explanation of a “biomechanical cause” for violent behavior produced a significant mitigating influence on sentencing, the researchers concluded.


The documentation of this leniency effect is “likely to accelerate the use of brain science in legal proceedings,” according to courtroom experts contacted by the Times.


A full report of the experiment appears in the journal Science, with a free abstract available clicking here. The NY Times report can be read by clicking here.





In Force Science News #211, transmitted Aug. 23, we mentioned that in Canada a panel of experts will be reporting next year on an independent, impartial exploration of the medical and physiological impacts of conducted energy weapons.


We should have stated that this 14-member group is officially sponsored by Defense Research and Development Canada, an agency of the Canadian Dept. of National Defense.


For more information about the assessment, click here.

© 2017 Force Science Institute Ltd.