Why bad information can linger in your brain

Editor’s note: This is column is produced by a collaboration between The Seattle Times Save the Free Press initiative and the University of Washington’s Center for an Informed Public.

As I search through the Yelp reviews of local Chinese restaurants looking for a place to order out, I come across a review that reports, “Minutes after leaving I can already feel the MSG hitting.” Someone else chimes in with “Now thirty minutes later, the MSG is giving me headaches, and my spine feels stiff.” 

These complaints represent the echoes of “Chinese Restaurant Syndrome.” This syndrome, originally reported in a flawed 1968 report, is said to develop shortly after the ingestion of MSG (aka monosodium glutamate), and involves a set of symptoms including headache, throat swelling and stomach pain developing shortly after the ingestion of the food additive, used for its delicious umami flavor. 

The story of Chinese Restaurant Syndrome provides an interesting example of something psychologists refer to as the “continued influence effect.” This effect refers to the observation that outdated or incorrect information can continue to influence our beliefs even after it’s been corrected. 

The continued influence effect manifests when we are presented with evolving information, such as with news updates around current events or with a changing scientific understanding around topics related to health. Knowing about this effect can help us understand how we’re all susceptible to the influence of outdated or problematic information, especially when trying to navigate the deluge of news and information we receive nowadays.

In the case of Chinese Restaurant Syndrome, controlled research studies conducted in the years since the original flawed report have found that for the vast majority of individuals, standard levels of MSG are unlikely to produce any of the negative symptoms associated with the syndrome. Since the 1990s, the Food and Drug Administration has given MSG the categorization of “generally safe for consumption” — a designation shared with other common food items like salt and cinnamon.

Scientists and researchers have been debunking MSG myths for decades. Yet, Chinese restaurants continue to be targeted, with many still removing this delicious addition from their foods. Why has it been so difficult to update our attitudes? 

In trying to answer this question, we can look back at a classic research study on this effect from 1994. In this study, research participants were asked to read a series of reports about a warehouse fire. These reports included information about volatile materials, like oil paint and pressurized gas canisters, found in a closet. Later, participants were given updated information that the closet was actually empty; there were no volatile materials found. However, despite this correction, participants still relied on the original reports when making later judgments, saying, for example, the reason they thought the fire was particularly intense was that oil fires are difficult to extinguish. 

This continued reliance on the corrected information was not due to failure to understand the new information; the majority of participants were able to accurately report that the closet was indeed empty when asked directly. Yet, they still relied on the retracted information in their future judgments related to the fire’s cause.

Instead, the continued influence effect can be thought of as result of how our brains store and update information. When we receive a correction about something we already know, we don’t simply erase the old information from our minds. Rather, representations of both the old information and its correction coexist in our brain’s knowledge networks, playing a role in guiding our future judgments and beliefs. We’re especially likely to rely on old information when it’s the only explanation we have, or the one that comes to mind the easiest. When searching for reasons why our stomachs hurt, the warnings of fellow Yelpers make a compelling argument when they’re the most plausible explanation we can think of.

The good news is that this tendency also lends itself to a solution: When giving a correction, also provide people with new information to take the place of the old. In the case of the warehouse fire study, researchers found that when, along with the corrections about the contents of the closet, they also shared an alternative potential cause for the fire — arson materials found elsewhere — participants relied less on the outdated information. Similarly, you might explain to people that perhaps the reason for their post-orange chicken funk isn’t the MSG, but instead that the dish they chose had a lot of oil, a culprit for many of the same symptoms. 

Understanding the continued influence of misinformation can also shed light on why other myths or outdated information around COVID-19, such as how it spreads or the effectiveness of masks, have been so persistent. The state of scientific knowledge and our understanding of COVID-19 changed rapidly over a short period of time. Corrections and changes to recommendations were plentiful, but the explanations were often poorly communicated and hard to follow, leaving many to continue to rely on what they first learned. 

In these instances, it can be helpful to understand that the failure to disregard outdated information is not a personal failing but instead a byproduct of how our mental systems work. So for now, I’ll forgive my fellow Yelpers for their flawed inferences and focus my energy instead on seeking out the best egg foo young to order for dinner — be it MSG-free or not.