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Post-booze blackout, how people fill in the blanks

Getting hammered to the point of not remembering much, if anything, about it is a pretty common experience for some people on college campuses or during a long holiday weekend. Reconstructing what happened during a bout of booze-fueled amnesia can either make for a hilarious movie plot like "The Hangover" or an interesting research project.

Although not inspired by the Hollywood blockbuster, a recent study looked at alcohol-induced memory blackouts hoping to learn how people "fill in the blanks" afterward and whether this information is accurate. Researchers found that people frequently turn to  unreliable sources to piece together these forgotten memories.

In the study, published in the journal Memory, 280 British college students completed an online survey. Students were asked whether they had experienced either a partial blackout  --  where they remembered bits and pieces of what happened after they started drinking, or a total one -- forgetting everything about what they did or saw until they woke up the next day.

Among the students who drank, 24 percent of them admitted to having a total blackout while 37 percent had a partial one. Drinking a lot within a short period of time typically causes a blackout, explains lead author Robert Nash.

Researchers found that blackout sufferers were somewhat more likely to ask people who had also been intoxicated for details of the hazy episode rather than asking people who weren't drunk but had also witnessed it. Nearly 44 percent said they had seen a photograph or video reminding them of what happened.

"I was surprised at how highly motivated people were to reconstruct these forgotten alcohol-soaked experiences, despite knowing that doing so can often lead to considerable embarrassment or panic," admits Nash, a lecturer in psychology at the University of Surrey in Guildford, England.

He says asking other people who were there is often the only way we can find out what happened. But that relying on friends or acquaintances who were probably drunk can make their recollections less than 100 percent reliable.

Unreliable sources can lead to memory errors and sometimes false beliefs about behaviors during a forgotten time-period. This may be true not only for boozy blackouts but for other past experiences, whether it's cobbling together childhood memories or even in cases of wrongful conviction.

Interestingly roughly three-quarters of the study participants admitted they might have unintentionally made up information when a friend passed out, such as claiming the person had sex with a stranger or puked on someone.

And nearly 17 percent of blackout sufferers later discovered they were misled by incorrect information, often coming from friends.

But having a blackout and being eager to know what happened, seems perhaps to change people's perspectives on whether a particular source could be trusted, Nash points out. "So we place faith in information sources that we would othewise consider highly untrustworthy."

His advice? "Be aware when reconstructing events of whether you are placing trust in a source because someone is truly reliable or because that person is the only option."

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