Force Science News

Force Science News #112: A Compilation of Important Memory Issues

[Editor’s note: Memory is often a wild card in officer-involved shooting investigations. Involved officers typically don’t remember certain things that happened or they remember them incorrectly or their recollections conflict with accounts of other witnesses. This is frustrating and often suspicious to investigators.

[Just how memory works is still the subject of intense exploration by neuroscientists. Much of what is known unfortunately has been slow to reach law enforcement circles. In this transmission, Force Science News presents 3 reports on recent memory-related developments that can help reviewers of force incidents better understand the challenges of accurate recall that they may confront.]

I. New report offers truths about memory for the legal system

A 52-page report on the complex and tricky nature of human memory has been compiled by experts from 6 countries to help judges, prosecutors, attorneys, and the police better understand and accommodate the realities of recollections involved in legal proceedings.

So far the document, “Guidelines on Memory and the Law,” prepared by the research board of the British Psychological Society, has been distributed only within England’s court system.

“But the content could help clarify many misconceptions about memory that hamper fair and impartial use-of-force reviews and trials in the U.S. and other countries,” says Dr. Bill Lewinski, executive director of the Force Science Research Center at Minnesota State University-Mankato.

“It’s not unusual in officer-involved shootings, for example, for shortcomings in officers’ memories or contradictions with what other witnesses remember to be regarded as evidence that officers are lying or being evasive, when what’s really involved is the basic, uncontrollable biology and psychology of memory itself.”

The full report—distilled from input by prominent memory scholars in the U.S., England, Scotland, Australia, New Zealand, and Israel—can be accessed by clicking here.

At the outset, the Guidelines present a list of “key points” about memory that are vital for participants in the legal system to understand. These include:

• Memories, unlike video or audio recordings, are not exact replications of events;

• Memories are shaped by the life experiences, training, biases, and attitudes that a person brings to the situation;

• Memories are fragmented and always incomplete;

• Memories are prone to error and are easily influenced by the environment in which they are recalled;

• The retention of highly specific details in long-term memory is unusual;

• Memories can be unwittingly modified by the type of questioning used to elicit them;

• Without trying to be deceptive, people can “remember” events that they have not actually experienced.

The body of the report then elaborates on these points, exploring the psychological nature of memory, the effects of trauma and stress on recall, memory idiosyncrasies in special groups such as children and seniors, techniques for interviewing witnesses, and memory reliability in lineups.

“The law generally is unaware of the findings from the scientific study of human memory,” the Guidelines state. It is “palpably clear” that there is insufficient understanding among the various components of the judicial system of “how our memories work, their limitations, properties, and failings…. [R]elying on uninformed evaluations of memory can only lead to unreliable judgments.”

An important point made in the report, Lewinski says, is that the setting, the timing, and the kind of questioning can either help or hinder a subject’s recall. “These factors can have a significant impact on the type and nature of information remembered,” he says. “How an officer is managed after a critical incident and the approach to mining his memory can make a big difference. An interview about a shooting may be the most important interview of an officer’s life and may be vitally important to the department as well. The department has an obligation to facilitate the best conditions possible for everyone concerned.”

The Guidelines “provide a far more rigorously informed understanding of human memory than that available from commonly held beliefs,” the authors claim. And as a result, they provide “a much firmer basis for accurate decision-making” where issues of memory are involved.

Memory research, of course, is ongoing. New discoveries may necessitate new interpretations. But for now, in Lewinski’s words, the Guidelines “reflect the state of the art on memory.”

II. Sleep loss tied to greater risk of producing false memories

Sleep deprivation can cause your brain to generate false memories, according to findings by a team of Swiss and German researchers. Extrapolated, their work supports the argument that OIS survivors should have time to sleep before being required to give statements about their encounter.

Researchers headed by Dr. Susanne Diekelmann of the Dept. of Neuroendocrinology at the University of Lubeck in Germany tested 86 male and 59 female volunteers ranging in age from 18 to 35 in a series of memory-related experiments.

The subjects were told to memorize “as accurately as possible” several lists of words. Some were given the words shortly before embarking on a normal working day; others got them just before retiring for a night’s sleep; and a third group was kept awake all night after learning their lists.

When tested, those who had been sleep-deprived showed a significantly higher incidence of false memory. That is, when they were shown lists that now included words they had not been given previously, they more often than the other volunteers “remembered” words they actually had not learned before.

This result, the researchers concluded, “indicates that sleep deprivation…critically enhances false memories.”

This pattern seems to hold even when the sleep deprivation does not occur immediately after learning. In a second experiment, the researchers allowed 2 groups of subjects to sleep the first night after memorizing word lists. The second night, one group again slept and the other was kept awake.

As before, the group that was deprived of sleep before attempting to retrieve memories produced more false recollections. “[I]t is specifically sleep deprivation at retrieval that renders subjects susceptible to false memories,” the researchers stated.

A factor that seems to improve memory despite fatigue is caffeine. The researchers kept 2 groups of volunteers awake during the night after learning the word lists. An hour before their memories were tested the next morning, 1 group was given 200 mg of caffeine, while the other group received a placebo.

“The ‘night-wake caffeine’ group exhibited a significantly lower false memory rate when compared to the ‘night-wake’ placebo group,” the researchers reported.

Interestingly, the subjects who produced more false memories across all the experiments did not admit to having any less confidence about their responses or feel that they were more often guessing in their answers than those whose memories were more accurate.

False memory creation may have to do, in part at least, with changes to the prefrontal regions of the brain, brought on by sleep loss interfering with “reality monitoring,” the researchers explained.

In the future, the research team recommends that more experimentation be done, particularly on false memories that may be generated during “free recall” of events, to supplement their experiments which were limited to “recognition memory.”

Nonetheless, they feel their current findings do have relevance to legal issues. “[O]ur results clearly show that sleep deprivation is [a] critical factor that must be avoided” during interviews and when soliciting witness testimony.

The researchers’ report of this study is online. Click here to read it now.

[Thanks to Acting Insp. Chris Butler of the Calgary (Alberta) Police Service for giving us the heads-up on this study. Butler was recently certified as a Force Science Analyst after completing training with the Force Science Institute.]

III. Even short-term stress can damage memory

Another memory study that may be relevant in critical incident investigations and assessments comes from the University of California-Irvine.

Researchers have long known that the increased production of certain hormones caused by stress over periods of weeks, months, and years can damage recall abilities. But now a new study has shown that chemicals released in response to acute, short-term stress can undermine memory too.

In animal studies, a research team headed by neuroscientist Dr. Tallie Baram discovered that acute stress stimulates the release of a chemical called “corticotropin releasing hormone” (CRH), which is different from the long-term stress hormone cortisol, commonly associated with memory damage.

When CRH is released in the hippocampus, the brain’s primary learning and memory center, it causes a rapid disintegration of “dendritic spines,” tiny membranous protrusions on hippocampal neurons. This, in turn, limits the ability of brain synapses, which are critical in forming and storing memories, to function properly.

When Baram’s team administered low levels of synthetic CRH to mice and rats, they watched “how the spines retracted over minutes.” Once the chemical was removed (comparable, it would seem, to stress being alleviated), “the spines seemed to grow back.”

The study offers “insights into why some people are forgetful or have difficulty retaining information during stressful situations,” according to Baram.

“Again,” says Dr. Bill Lewinski of the Force Science Research Center, “we have evidence suggesting that important negative influences on memory are often beyond the control of an officer who has been involved in a high-stress confrontation. This is the bottom line that needs to be taken into account when an officer’s truthfulness or candor is being judged.”

The California researchers, meanwhile, are hopeful that their findings eventually will lead to drug therapy that can nullify the adverse effects of CRH.

A full report of their study can be found online. [Click here to read it now.]

But beware: it’s a jungle of highly technical jargon!

[Thanks to trainer Randy Dickson of Critical Interaction Associates, author of the book Officer-Involved Shootings and Use of Force: Practical Investigative Techniques, for tipping us to this study.]

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Written by Force Science Institute

December 19th, 2008 at 2:19 pm

Posted in Force Science News