Facebook is taking users on a nostalgia trip this week as it celebrates its 10th birthday. The social media giant is asking people to click on "A Look Back," a program that quickly produces a one-minute slideshow that's basically a mini-portait of the user's life. The portrait is conveyed with a sample of the words and photos that the user has posted since joining Facebook. The slideshow features sub-heads like, "Your First Moments" and "Your Most Liked Posts." The short story comes with a sentimental soundtrack.
You may be asking, "How did Facebook figure out how to summarize my life online? And how do they do it so quickly?" Those are the questions I had after I clicked on the program. I sought answers from Yoav Freund, a UC San Diego computer scientist who says that the mini-portraits represent a modern example of a decades-old form of linguistics modeling known as "bag-of- words." Scientists came up with algorithms that search documents for specific words, and combinations of words, and the frequency with which the words appear. This helps people classify the content of such things as legal filings and legislative bills.
Freund says the nature and sophistication of bag-of-words modeling has evolved over the years. Companies like Facebook can easily use algorithms to spot words that are common on one user's newsfeed, but not on others. This helps reveal what's important to a specific user. Algorithms also look for specific words that could carry deep meaning, such as love, hate, family and friend. That helps to further classify a person. So does the size and make up of a user's followers, and the response to their posts. The algorithm pays particular attention when Facebook users who rarely make a comment online say something on another person's feed. The algorithm gives extra weight to those posts because they could be insightful. The programs also pick up on the sentiments that are expressed. That gets processed under sentiment analysis, a form of machine learning.
Freund notes that algorithms aren't very good at spotting things like the use of irony. But he says the modeling can create a fairly good portrait.
Ramesh Rao agrees.
Rao is director of the UC San Diego division of Calit2, a technology, health and education think tank.
"It's kind of scary; the nature of something as unique as a human can be inferred by an algorithm," Rao says. "We're probably easier to figure out than we thought."
Rao says the use of the "Like" button on Facebook is particularly important.
"You're leaving clues about yourself in the minds of other people," Rao says. "It is like making eye contact. It reveals a lot."