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Sleep Deprivation Increases Susceptibility to False Memories
October 7, 2014
According to the Innocence Project, an organization dedicated to exonerating individuals who have been wrongly convicted of serious crimes, eyewitness misidentification testimony is the leading cause of wrongful convictions in the United States. This statistic does not surprise Elizabeth Loftus, a professor of cognitive science and law at the University of California at Irvine. Over the past several decades, her research in human memory has shown that memory is not reliable. Her studies have shown, time and time again, that memories can be altered, often by mere suggestion, and under a variety of different circumstances. New research from her lab suggests that sleep deprivation can also make people more susceptible to the creation of so-called false memories.
Lack of sleep and memory
As any mother of a newborn can tell you, lack of sleep can wreak havoc on cognitive functioning. Many studies in both animals and humans have shown that sleep deprivation is detrimental to basic cognitive skills like vigilance, alertness and attention. But new work shows that sleep is also important to memory. Ted Abel, a neuroscientist at the University of Pennsylvania, recently found that even as little as three hours of sleep deprivation is sufficient to impair memory storage in rodents.
“What this tells us is that sleep is beneficial to memory. Sleep deprivation can block the formation of memories,” he says. “We see that sleep is necessary for memory and, in general, an important part of a healthy, plastic brain.”
Recent studies show that sleep appears to be just as crucial to healthy human memory, from storage to retrieval. While many of us know that sleep deprivation results in many negative cognitive consequences, there was very little information about what role it might play in memory distortion, or the creation of false memories, says Steven Frenda, a former graduate student in Loftus’ lab who now is a postdoctoral fellow at the New School for Social Research.
“There is surprisingly little research on the link between sleep deprivation and suggestibility,” he says. “And it’s an important link to understand because chronic sleep deprivation is increasingly prevalent and in some contexts, like criminal trails or clinical decision making, memory errors can have serious consequences.”
Sleep deprivation and false memories
To test the idea, Frenda and colleagues showed people photographs of events, such as a man stealing a wallet, after a full night’s sleep or a night of no sleep at all. They were then asked to read a written narrative that researchers said went with the photograph but included a few pieces of subtle yet misleading information. For example, after viewing a photo of a hand taking a wallet out of a breast pocket, and then reading the misleading narratives, individuals might later state that the wallet was taken from the back pocket. After seeing the photograph and reading the accompanying narrative, they were given an extensive memory test that focused only on the original photograph. The results were published in the July 16, 2014, issue of Psychological Science.
“We found that the participants who were sleep deprived were significantly more likely to incorporate parts of the misleading narratives into their memories for the photographs,” says Frenda.
But when participants looked at the photos while they were rested, before being put into the sleep or no sleep group, and then read the narratives the next morning, they did well on the memory test. “When the procedure was done this way, there was no effect at all of sleep deprivation on false memories,” he says. “What really seemed to matter was whether people were sleep deprived during the initial experience.”
Sleep deprivation and eyewitness testimony
Frenda says this study fits well with previous work that shows how malleable memory can be—though he would like to do more work to better understand the relationship between sleep and false memory, and when it has the most power to distort what we remember. Still, he thinks this finding has important implications for the legal and law enforcement communities.
“Memory is always changing and being reconstructed, each time we remember. It is not a recording of what we see and experience. It can be influenced by external information, and in some situations, we become more vulnerable to those influences,” says Frenda. “It’s important for legal communities to continue to understand, first and foremost, how fragile and corruptible people’s memories are. Even subtle or accidental suggestions can have dramatic effects.”
Loftus cautions that eyewitness testimony remains an important part of solving crimes—and some of it is very good. But the legal community should be aware of the phenomenon of false memory and, before fully trusting an eyewitness account, make sure they understand “how the sausage was made.”
“This study makes me think about these grueling interrogations of suspects, which are known to go on for hours and hours into the wee hours of the morning. Those kinds of interrogations may ultimately lead to false memories or false confessions,” she says. “And I think law enforcement needs to be aware of this situation and maybe take extra steps to make sure not to do anything that is leading or misleading under those circumstances.”