10 January 2010 ~ 1 Comment

On Courage and Netflix

Netflix might have a well-publicized recommendation system although they never cease to make puzzling recommendations (also well publicized).

For the uninitiated, Netflix takes a guess at whether or not you’ll like a movie and indicates that guess by the number of red stars present below a movie (yellow stars represent your ratings, none of which appear in the image that follows).

Here’s an example (note: I have no idea what these movies are, or what they’re about).

Let’s imagine Netflix as a helpful assistant, and how that conversation would go.

Rob: “I have a few hours to kill for a layover and free wifi.  Computer, I’ve told you what I think of 1,004 movies and I’m not sure what’s been recently released.  Can you suggest some?”
Assistant: “Sure Rob, I’d be happy to.  Here are 5 movies.”
Rob: “Thank you computer.  Actually after looking at these movies, I’m not sure I’d like to watch any of them.  Gallipoli isn’t quite the war movie I enjoy.  The others aren’t even close to the types of movies I would be interested in.”
Assistant: “That’s what I suspected before I showed them to  you.”

An awkward interaction.

Rather than display 5 movies it thinks I’ll rate “Hated It” or “Didn’t Like It”, is there another alternative?

According to Wikipedia, in November 2008 there were over 17,000 titles in the Netflix Instant catalog.  Netflix is certainly willing to show me older movies that have just become available instantly (e.g. 1981’s Gallipoli).  How about continuing backwards in reverse chronological order until it finds things five items (to fill one page width) it thinks I’d rate at least three stars?

Put another way, I’d like to say “Computer, when you think I’ll rate something one or two stars you’ve been correct so often I wish you wouldn’t second guess yourself.  I’ve already hired you and put in the effort to tell you over 1000 of my preferences.  That’s a vote of confidence that in your ability to recommend movies.  Have the courage of your convictions to avoid showing me movies I won’t enjoy.”

I’ve taken the time to rate over 1000 movies.  If I didn’t at least somewhat find the Netflix recommendation system helpful, I wouldn’t have done that.  I’d like Netflix to respect that time by choosing to avoid showing me movies it guesses I will either “Hate” or “Not Like”.

One Response to “On Courage and Netflix”

  1. Mike Berggren 27 January 2010 at 11:42 am Permalink

    Ahh, you’ve come across one of my greatest pet peeves with collaborative filtering in general — the blatant inefficiency of the system. Mathematical algorithms aside, most systems that try to leverage CF either:

    1) Make no assumptions (defeating most use cases)


    2) Try for a “blended” recommendation approach that is equally awful.

    I hope it improves at some point but I suspect it won’t any time soon…

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