“Under cannabis, users can easily accept fake truths for true memory,” study finds
Cannabis can not only dull the memory, but it may also prompt the brain to make up false ones.
According to a new study published this week in the journal of the Proceedings of the National Sciences Academy of the United States of America (PNAS), cannabis can increase a user’s susceptibility to false memory.
Participants who took even just one hit from a cannabis joint experienced double the number of false memories than those who smoked a placebo when presented with a virtual reality scenario, according to study author and Maastricht University psychopharmacology professor Johannes Ramaekers.
“We are all prone to the formation of false memories, independent of cannabis use,” Ramaekers toldCNN. “The susceptibility for false memory, however, increases with cannabis. Under cannabis, users can easily accept fake truths for true memory.”
Participants performed memory-related tasks such as recalling items on a written list of words with a common theme, and answering questions about a virtual-reality fight they were shown. They were then fed misinformation via false testimony from other “witnesses” and suggestive questioning.
Those who had inhaled THC were more likely to agree with suggestions and demonstrated more false memories than other participants while inebriated.
“Across all methods, we found evidence for enhanced false-memory effects in intoxicated participants,” researchers write. “Specifically, intoxicated participants showed higher false recognition in the associative word-list task both at immediate and delayed test than controls. This yes bias became increasingly strong with decreasing levels of association between studied and test items.”
Researchers say that the results are particularly pertinent for law enforcement.
“False-memory effects were mostly restricted to the acute-intoxication phase. Cannabis seems to increase false-memory proneness, with decreasing strength of association between an event and a test item, as assessed by different false-memory paradigms. Our findings have implications for how and when the police should interview suspects and eyewitnesses.”
Co-author Elizabeth Loftus concurs.
“This new work is suggesting authorities need to be extra careful when interviewing somebody,” Loftus told CNN, adding that law enforcement might want to keep witnesses “from a situation where they might be exposed to suggestive information that could contaminate their memory.”
Written by Emma Spears