Movie Lovers (and Code Monkeys) Rejoice: Netflix Prize Won

Brow Beat
Slate's Culture Blog
June 29 2009 1:34 PM

Movie Lovers (and Code Monkeys) Rejoice: Netflix Prize Won

And all along, the secret was right there in the stochastic gradient descent. On Friday, a team called " BellKor’s Pragmatic Chaos" declared itself the winner of the $1 million Netflix Prize , the contest to improve the site’s existing movie recommendations formula by 10 percent. We don’t yet know exactly how the likely winners did it—the winning team is keeping quiet, since other contestants still have a month to beat their entry, according to the contest rules. We do know this: The contest probably wasn’t won thanks to a revolutionary idea about how we form our taste in movies.


While such a concept may still be out there, the Netflix Prize champs appear to have notched a major victory for computer science over psychology. That seems like a safe conclusion based on progress reports team members have published over the years. For a taste, try this sentence: "The values of the parameters are learnt by stochastic gradient descent with weight decay on the Probe data."  


I’m sure BellKor’s final paper will contain some insights into the psychology of taste, so long as you’re willing to ponder the math and computing behind it. A 2008 paper (PDF), for example, outlines how to represent the ebb and flow of a movie’s popularity over time, as well as a model for how an individual’s rating technique evolves. ( Cinematch , the model that Netflix uses today, is a simpler formula that correlates lots of data to predict your preferences based on your past ratings.)

As the Times noted over the weekend, the tentative winners are a fusion of four previously independent teams "made up of statisticians, machine learning experts and computer engineers." The fact that it took the combined powers of four teams to crack the 10 percent ceiling is another telling sign that the Netflix contest won’t produce some elegant, easy-to-parse theory of movie-watching. That shouldn’t diminish the accomplishment. Even if we won’t understand why it works, we should expect real results—that is, smarter recommendations—as soon as the BellKor et al. solution is implemented. The Netflix Prize is a good reminder that the human brain is an extremely powerful computer capable of juggling hundreds of variables, even when it’s thinking about how much it likes Weekend at Bernie’s II .

Chris Wilson is a Slate contributor.



Smash and Grab

Will competitive Senate contests in Kansas and South Dakota lead to more late-breaking races in future elections?

Stop Panicking. America Is Now in Very Good Shape to Respond to the Ebola Crisis.

The 2014 Kansas City Royals Show the Value of Building a Mediocre Baseball Team

The GOP Won’t Win Any Black Votes With Its New “Willie Horton” Ad

Sleater-Kinney Was Once America’s Best Rock Band

Can it be again?


Forget Oculus Rift

This $25 cardboard box turns your phone into an incredibly fun virtual reality experience.

One of Putin’s Favorite Oligarchs Wants to Start an Orthodox Christian Fox News

These Companies in Japan Are More Than 1,000 Years Old

Trending News Channel
Oct. 20 2014 6:17 PM Watch Flashes of Lightning Created in a Lab  
  News & Politics
Oct. 20 2014 8:14 PM You Should Be Optimistic About Ebola Don’t panic. Here are all the signs that the U.S. is containing the disease.
Oct. 20 2014 7:23 PM Chipotle’s Magical Burrito Empire Keeps Growing, Might Be Slowing
Oct. 20 2014 3:16 PM The Catholic Church Is Changing, and Celibate Gays Are Leading the Way
  Double X
The XX Factor
Oct. 20 2014 6:17 PM I Am 25. I Don't Work at Facebook. My Doctors Want Me to Freeze My Eggs.
  Slate Plus
Tv Club
Oct. 20 2014 7:15 AM The Slate Doctor Who Podcast: Episode 9 A spoiler-filled discussion of "Flatline."
Brow Beat
Oct. 20 2014 9:13 PM The Smart, Talented, and Utterly Hilarious Leslie Jones Is SNL’s Newest Cast Member
Oct. 20 2014 11:36 PM Forget Oculus Rift This $25 cardboard box turns your phone into an incredibly fun virtual-reality experience.
  Health & Science
Medical Examiner
Oct. 20 2014 11:46 AM Is Anybody Watching My Do-Gooding? The difference between being a hero and being an altruist.
Sports Nut
Oct. 20 2014 5:09 PM Keepaway, on Three. Ready—Break! On his record-breaking touchdown pass, Peyton Manning couldn’t even leave the celebration to chance.