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*This piece was originally published on May 17th, 2019*

If you have that gnawing feeling that you’re forgetting something, chances are you’re right. And it may not be your keys, but something a little bigger. César Hidalgo, director of MIT’s Collective Learning Group, explains how society experiences generational forgetting. 

Hidalgo says: even if you have a pristine memory, time greatly impacts the names, books, movies, and historical events that are common knowledge at any given moment. Researching how culture gets passed down (or doesn’t) from generation to generation can tell us more about why some famous people stay relevant, while others seem to fade away.

Three Takeaways:

• How long does it take for something famous to become forgotten? Hidalgo graphed it - and the process follows a curve. Take a popular song, for example. Hidalgo found that songs have a period of up to 5 years of lasting in our communicative memory. Being in our communicative memory means that we are still talking about the song in our day-to-day conversations. However, after 5 years, once-popular songs enter our cultural memory. This stage is where what was previously in pop culture becomes lives in materials like recordings, books, media, etc.
• Hidalgo said that there is not a definitive reason for why famous people - or famous movies or songs - lose their popularity. One theory is that new content begins to push out the old content. Another possibility is that when people of a certain generation begin to die, many of their cultural touchstones also begin to diminish in importance. 
• How do we, as a society, determine who deserves to be remembered throughout history? Hidalgo believes that this is not just a question about memory and forgetting, but also about morals. Since morals change over time and are culturally learned, Hidalgo says that it does not make sense to use our current values to judge people at other points in time.

More Reading:

• Scientific American reports about collective memory and how it shapes history.
• Read about the TikTok takeover, and how the app can make it hard to remember where a piece of media originated.
• Interact online with Hidalgo’s Pantheon project. It calculates who the most famous people are, according to different factors like place and time.