Did I do that? The psychology of alcohol-induced blackouts

The morning after. Photo credit: Sophie Scott

When our autobiographical memory lets us down, how do we reconstruct the lost chapters? Two psychologists Robert Nash and Melanie Takarangi have identified the perfect population for investigating this very question. "Colleges and universities teem with amnesiacs of a sort," they write, referring to the large number of students who drink quantities of alcohol sufficient to wash away whole episodes from memory.

Nash and Takarangi surveyed 280 students about their alcohol-induced blackouts and found the students were highly motivated to reconstruct what happened. In fact, their desire to fill in the blanks often led them to rely on unreliable sources, such as drunk friends, and to therefore form false memories of the blacked-out period. "Such errors could have enormous impact," the researchers said, "not least because during blackouts people engage in ... risky behaviours such as drug use, fighting and sexual intercourse."

Of the surveyed students, 85 per cent described themselves as drinkers and 61 per cent reported having experienced a total or partial memory blackout whilst drunk. Men were more likely to have had a blackout than women (75.4 vs. 56.7 per cent).

The researchers presented the students with a hypothetical party scenario in which they'd experienced a blackout and asked them to say how motivated they'd be to try each of eight strategies for filling in the blanks. Unsurprisingly, the students tended to say they were motivated most strongly to seek the help of a sober friend who'd been there. Other favoured strategies included: checking photos or videos, consulting a drunk friend who'd been present, and thinking hard about what had happened. Less favoured were: returning to the scene of the party, asking a sober or drunk party guest other than a friend.

Comparing students who'd experienced blackouts in real life with those who hadn't, an intriguing difference emerged - the blackout sufferers were more motivated to rely on drunk friends and there was a slight trend for them to judge drunk friends as more reliable. Blackout sufferers also judged drunk non-friends as more reliable than did non-sufferers.

Turning to the students' reports of how they'd actually attempted to reconstruct boozy blanks in real life, consulting a drunk friend was more common than consulting sober people (77 per cent vs. 69.6 per cent). Forty-three per cent said they'd seen a photo or video of what had happened on at least one occasion; 20.9 per cent had found other physical evidence.

The blackout sufferers said that their reconstructions of boozy blanks sometimes turned out later to have been inaccurate - 16.9 per cent admitted to this having happened, and they said the most frequent reason was relying on drunk friends. Some of the students (11.5 per cent of blackout sufferers) said they'd previously had confidence in the incorrect account of what had happened; 3.4 per cent said they'd actually formed (false) memories for events that hadn't happened.

A curious paradox to emerge in the results was that students who said they'd relied on drunk friends in the past were more likely to admit having been exposed to misinformation, but at the same time were more confident in the future reliability of drunk friends and non-friends. The researchers speculated that perhaps drunk friends had been the only source of information in the past and "because people are highly motivated to reconstruct forgotten experiences, it is possible that such circumstances might encourage individuals to believe that the available sources of evidence are more reliable" - a kind of self-serving bias.

Finally, Nash and Takarangi asked the students if they'd ever knowingly given blackout sufferers false information about blanks in their memories. Seventy-six per cent of the sample said they might have unintentionally done so; 13.7 per cent said they'd deliberately made up details; 7.1 per cent had fabricated an entire event.

The researchers end their study on a sombre note. "We can only speculate about the consequences that blackout sufferers' false beliefs and memories could have in some cases," they said. "For instance, archival studies suggest that numerous innocent people have confessed to crimes after being led to believe they committed acts while drunk, and flawed reconstructions might also lead blackout sufferers to make false accusations against others."
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Nash, R., and Takarangi, M. (2011). Reconstructing alcohol-induced memory blackouts. Memory, 19 (6), 566-573 DOI: 10.1080/09658211.2011.590508

Post written by Christian Jarrett for the BPS Research Digest.