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High-Witnesses: New Study Reveals How Marijuana Consumers Can Help Solve Crimes



It’s not uncommon for people who witness crimes to report being under the influence of some drug. But until recently, research has primarily focused on the effects of alcohol intoxication on eyewitnesses.

A recent study, published in the journal Applied Cognitive Psychology, attempted to fill that information gap, as eyewitness reliability can be a key factor in criminal justice proceedings. The findings appear to challenge stoner stereotypes, revealing that marijuana consumers aren’t actually liabilities when it comes to crime solving.

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The researchers wanted to figure out how cannabis use impacted accurate or incorrect recall of details, the identification of individuals in a lineup setting and the confidence of participants in that lineup identification. To do that, they recruited 120 adults (a mix of sober and intoxicated) at a coffee shop in Amsterdam and showed them a two-minute video of a convenience store robbery.

After viewing the video, participants were asked to freely recall as many details as they could remember. This was the one test where cannabis consumers fell short compared to sober participants. Those who were intoxicated “reported significantly fewer correct detail than did sober participants,” the researchers wrote. 

That’s not to say stoned participants remembered more inaccurate details; rather, it’s a matter of quantity. They just didn’t remember as many correct details compared to the control group.

And of the four tests that the researchers conducted, this test was the outlier. People who had smoked marijuana—regardless of the dose—were just as accurate and inaccurate for the details they did recall.

“Thus, cannabis intoxication was not associated with either a decrease in correct identifications or an increase in false alarms.”

Things got even more interesting when it came to the lineup portion of the study. Contrary to expectations, marijuana consumers were just as likely to accurately identify the suspect in the video from a photo of six similar looking individuals. But perhaps more surprising, they also reported higher confidence in their lineup identification compared to the control group.

“The level of confidence expressed in a lineup identification can have a significant impact on judgments about the credibility of the eyewitness and the likely guilt of the suspect,” the researchers wrote. “This finding is not in line with the hypothesis that intoxicated participants would compensate for anticipated poorer performance by adjusting their confidence ratings downward.”

The study was first published in April but seems to have gone mostly unnoticed until The British Psychological Society picked it up this week.

The researchers proposed two theories about about the study’s counterintuitive finding: First, it’s possible that the marijuana itself was responsible, as cannabis is believed to enhance internal focus. Second, participants who consumed cannabis might be more acutely aware of assumptions about marijuana use as it applies to cognitive functioning—and so they paid closer attention to “internal cues.”

While there’s certainly evidence suggesting that getting high can temporarily impair a person’s short-term memory, this new study adds to the growing body of literature revealing how marijuana use might actually boost certain aspects of a person’s cognitive functioning.

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Kyle Jaeger is Marijuana Moment's Sacramento-based managing editor. His work has also appeared in High Times, VICE and attn.


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