Marijuana can really mess with your memories, according to science.
Research from Maastricht University, University of California, Irvine (UC, Irvine), and other partners suggests that people are far more likely to form false memories when they are high.
They found that just one puff of weed made people very suggestible, even to ‘planted’ memories as the result of leading questions than were sober test subjects.
The findings have concerning implications for the testimonies of eye witnesses of crimes, who are not usually required to be drug-tested in the field before giving police descriptions of what they saw.
And for the growing number of people who use marijuana, it could be a step to solving the mystery of why regular use of the drug is linked to poorer memory and cognitive issues.
People who use cannabis are vulnerable to forming false memories, new research suggests
The more that scientists learn about memory, the clearer it becomes that it is indeed a pliable thing.
Not at all like the filing cabinet memory was once imagined as, we now know that every time we try to pull as memory from one of those drawers, we’re letting new bits of information slip into it too, distorting the recollection.
And all sorts of tricks, moods and environmental stimuli can make us more or less vulnerable to these mis-remembrances.
In fact, one of the study’s co-authors, Elizabeth Loftus, is effectively the architect of the downfall of eyewitness testimony.
Her work from the 1970s showed that a carefully crafted line of question could warp a person’s recall of a details of an event.
Going several, controversial steps further, she also showed that people could be convinced that they had entirely fictionalized memories.
Her studies were a turning point for psychologists’ understanding of memory, and for one of the bedrocks of the legal system.
Dr Loftus’s testimony has also overturned cases against accused child abusers and other criminal.
She’s drawn international attention and ire as an expert witness for the defense in the trials of divisive figures such as OJ Simpson, Ted Bundy, Michael Jackson and, just days ago, Harvey Weinstein.
But she and her team wanted to look at how weed, used by some 183 million peple worldwide, might affect memory and testimony, too.
They recruited 64 adults to test the effects of cannabis.
Half were given a controlled dose of marijuana, while the other half got a placebo.
All participants were then subjected to two experiments.
In the first, they were given a list of related words to remember.
Shortly thereafter they were asked if a certain words were on the original list of 15.
Those who had used weed were far more likely to falsely recall words as being in their initial set that were not, in fact.
In the second experiment, each participant wore a virtual reality headset. In one experiences, they committed a crime, and in the other, they were witnesses to a crime – a railway station fight.
Immediately afterwards, everyone was questioned about what they did and saw.
People that were high falsely recalled details of the experiences that hadn’t occurred or been present at a much higher rates than their sober counterparts did.
Encouragingly, everyone’s recall a week later was imperfect, but about equally so.
‘Our findings show that it would be better for police officers and investigators to postpone the questioning of eyewitnesses and suspects who are under the influence of cannabis until they are sober,’ said study co-author, Jan Ramaekers.
‘People under the influence of cannabis should actually be treated as a vulnerable group in a criminal investigation, comparable with children and the elderly.’