It can be challenging to recall the details of what you've witnessed and the specific locations where you encountered them. This difficulty arises due to the limited capacity of human source memory. While our brains excel at retaining visual and auditory information, they struggle when it comes to preserving the origins of that information. Source memory tends to mature relatively late and is susceptible to the effects of aging. The prefrontal cortex is responsible for this function, and it's one of the slowest maturing areas of the brain.

Individuals with damage to the prefrontal cortex exhibit impaired source memory. In a 1997 experiment, researchers divided patients into two groups, where one group was read a sentence by a male speaker, and the other group heard the same sentence read by a female speaker. Interestingly, the patients were able to recall the content of the sentence but struggled to remember the gender of the reader. However, it is worth noting that even healthy individuals faced a similar challenge in remembering the source. While they could recollect the story itself, they encountered difficulty recalling the specific person who shared it with them.

I often struggle with source memory myself. I was watching a drama last week and couldn't remember which episode I liked a line from. It took me six episodes of re-watching before I finally found the line. I wouldn't have had to go through all that trouble if I had captured or written down a memorable scene as soon as I saw it. Whether you're reading a book or watching a movie or TV show, it's important to take notes whenever you see something you want to remember so you don't get lost in the shuffle. There is no pill to improve your memory for sources. Notes are the only answer.

The problem of poor source memory has more serious consequences. It makes it difficult to separate fact from fiction. This is what happens when you see a scene in a movie or TV show that isn't true. Your brain only remembers the content of the information, not the source, so you can end up accepting a fictionalized version of the story as if it were the truth. For example, a patient with prefrontal lobe damage from a 40-year-old spy movie was reported to believe that a building near his home was built for evil purposes. This delusion was caused by forgetting the source of the information, which was a movie scene. Even healthy people are not immune to such distorted memories. In an experiment, college students were found to be more likely to accept fiction in a movie than fact, even when they were told beforehand that the movie contained untruths.

In the ancient times, remembering the content might have been more important than the source for survival. The information that there was a tiger near the cave was more meaningful than who told you about it. That's not the case now. In a world of fake news, remembering sources and fact-checking are essential. Always make sure what you know is true.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness and medications. This column was originally published in Korean in Joongang Ilbo on June 8, 2023. – Ed.