Using a second language can help reduce false memories

Do you ever swear you put your keys in your bag when you actually left them at home? We don’t usually realize when our brains misremember a past event — in other words, when they create a false memory. Thinking in a second language may help prevent this from happening, according to the surprising results of a recent study by University of Chicago psychologists. They found that people are less vulnerable to false memories when using their second language, probably because a second language forces your brain to work more deliberately and accurately. 

“When you’re working in a foreign language, you’re more likely to scrutinize your memory,” explains David Gallo, a neuroscientist at the University of Chicago who conducted the study with his colleagues Boaz Keysar and Leigh Grant. 

Thinking in a second language can help avoid false memories in many situations, from casual conversations with friends and family to eyewitness testimony in court or international negotiations using interpreters, according to the psychologists. “It’s a really important phenomenon,” Keysar says. 

In their experiment, the psychologists administered two tests aimed at implanting false memories in 120 people who spoke Mandarin Chinese as a first language and English as a second language.

In the first test, the participants were asked to remember a carefully crafted list of related words in English or Mandarin, but with one obviously related word missing. For example, “bed,” “awake” and “rest” would be on the list, but not “sleep.” The researchers then asked the participants to recall all the words on the list and also any words that were related to the list but absent. They discovered that participants using their second language, English, were better at placing the missing word correctly on the absent list.

The results were similar in the second test, in which the participants watched a silent video of a crime, then heard an audio recording describing the crime but with false details about the scene that were inconsistent with the video. The participants were then quizzed about the video in the language they heard the recording in. Those who heard audio in their second language were less likely to be misled by the lies.

Previously, some researchers had hypothesized that a person’s knowledge of word associations — your mental mind map — is weaker in a second language, so people are less likely to recall a word absent from a list. But the University of Chicago experiments suggest something else is happening. Theirs were the first false memory experiments to ask participants to write down words that should have been on the list but weren’t. Even in their second language, people wrote down the absent words, showing their associations were still strong.

This has led the psychologists to a new hypothesis called memory monitoring. This means the brain is more aware of what’s going on behind the scenes and is paying attention to memories more when working in the second language. “By controlling the association information, that’s much more compelling evidence that there is monitoring,” explains Jen Coane, a psychologist at Colby College and an expert in false memory.

Through this evidence of memory monitoring in a second language, the study also helps to support a prevalent theory in neuroscience: We have a more intuitive “fast brain” and a more deliberate “slow brain” that are used for different tasks. For example, when you recognize a melody you’ve heard before, that’s your fast brain. You immediately recognize that you’ve heard the music before. When you try to remember what song it’s from, that’s your slow brain. You need to take time to deliberately think about the song. Memory monitoring comes from your slow brain.

“The idea is that the foreign language helps you to slow down and consider the information that you are sifting through,” says Columbia University psychologist Miguel Arce Rentería, an expert on bilingualism and the brain who was not part of the Chicago study. 

But there is an important caveat, Arce Rentería adds. Working in a second language will not improve your memory overall; it will just reduce false memories. People usually perform worse on memory tests in their second language, probably because their brains are already working harder to focus on the language and have less room for other functions, he explains.

These findings open the door for more questions about the effects of bilingualism on the brain, such as how different kinds of word associations may affect memory monitoring differently, how the effects of bilingualism might be different with different languages and how it may affect cognitive decline in aging. “We haven’t answered all the questions,” says Coane. “That’s what makes the field so exciting.”