Khalid El-AriniCarnegie Mellon University

Joint work with:Ulrich Paquet, Ralf Herbrich, Jurgen Van Gael, Blaise Agüera

y Arcas

Transparent User Models for

Personalization

Personalization is ubiquitous.

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• YouTube: 72+ hours/minute of new video• Facebook: 950 million+ users• Twitter: 400+ million tweets/day• Shopping:

[1994]: 500K unique consumer goods sold in U.S.[2010]: Amazon alone offered 24 million.

Personalization is invaluable.

Keyword search is not enough.

Personalization is often wrong.

- J. Zaslow, November 26, 2002

“Basil…is not a neo-Nazi. Lukas…is not a shadowy stalker.David…is not Korean.

intent on giving them such labels.”

“there's just one way to change its mind: outfox it.” - J. Zaslow, November 26, 2002

What recourse do we have?

Can we do better?

You behave like a

vegan hipster

Vegan? Really? Why?

You: • tweeted with #meatlessmonday• follow @WholeFoods• …

We propose an alternative.

Why am I getting this?

We propose an alternative.

Why am I getting this?

You behave like a

Brooklyn hipster

Goal: Achieve transparency via interpretable user features, learned from user activity

You behave like a

Brooklyn hipster

Goal: Achieve transparency via interpretable user features, learned from user activity

Badges

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Approach Model Experiments Summary

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1. Define a vocabulary of badges

Apple fanboy

…

vegan runner photographer

Rich, interpretable and explainable

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1. Define a vocabulary of badges

2. Identify exemplars

How do I find vegans?

observed label

Take advantage of how users describe themselves

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Most vegans don’t label themselves as “vegan” on Twitter…

we want to infer the attributes of these users

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1. Define a vocabulary of badges

2. Identify exemplars3. Model characteristic

behavior• Hashtags #meatlessmonday• Retweets RT @WholeFoods

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Approach Model Experiments Summary

• We have no negative training examples.Use a generative model.

• Actions can be explained by multiple badges, even for the same user.

Noisy-or to combine badges.• How do we deal with user corrections?

Observing a latent variable.

Model sketch

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i=1…B

B badges

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u=1…N

i=1…B

N users

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u=1…N

i=1…B

F actions j=1…F

j=1…F

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bi(u)

u=1…N

i=1…BDoes user u have badge i?

j=1…F

j=1…F

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bi(u) λi(u)

u=1…N

i=1…B

j=1…F

j=1…FDoes user u have label for

badge i in his profile?

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aj(u)

bi(u) λi(u)

j=1…F u=1…N

i=1…B

Has user u performed action j?

j=1…F

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sij

aj(u)

bi(u) λi(u)

j=1…F

j=1…F

u=1…N

i=1…B

Does badge i explain action j?

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sijφij

aj(u)

bi(u) wi(u)

αφβφj=1…F

j=1…F

u=1…N

i=1…B

What’s the probability that a user with badge i performs action j?

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sijφijφbg aj(u)

bi(u) wi(u)

αφβφj=1…F

j=1…F

u=1…N

i=1…B

What is the background probability for each action?

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sijφijφbg aj(u)

bi(u) wi(u)

αφβφj=1…F

j=1…F

u=1…N

i=1…B

noisy or:Can at least one of my badges (or the background) explain it?

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sijφijφbg aj(u)

bi(u) λi(u)

αφβφj=1…F

j=1…F

u=1…N

i=1…B

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sijφijφbg aj(u)

bi(u) λi(u)

αφβφj=1…F

j=1…F

u=1…N

i=1…B

Beta priors to control sparsity

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sijφijφbg aj(u)

bi(u) λi(u)

γiT γiF

αφβφ

αT βT αF βF

j=1…F

j=1…F

u=1…N

i=1…B

Beta prior to encode low recall (e.g., 10%)

Beta prior to encode high precision

(e.g., 99.9%)

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ηisijφijφbg aj(u)

bi(u) λi(u)

γiT γiFωi

αφβφ

αη βη αω βω αT βT αF βF

j=1…F

j=1…F

u=1…N

i=1…B

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• Collapsed Gibbs sampler (with MH steps)

Inference

sijφijφbg

bi(u)

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ηisijφijφbg aj(u)

bi(u) λi(u)

γiT γiFωi

αφβφ

αη βη αω βω αT βT αF βF

j=1…F

j=1…F

u=1…N

i=1…BYou behave like a

vegan hipster.

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ηisijφijφbg aj(u)

bi(u) λi(u)

γiT γiFωi

αφβφ

αη βη αω βω αT βT αF βF

j=1…F

j=1…F

u=1…N

i=1…BYou behave like a

vegan hipster.

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Approach Model Experiments Summary

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• Start with 7 million Twitter users• Manually define 31 sample badges

by specifying labels

Data description

• Start with 7 million Twitter users• Manually define 31 sample badges by

specifying labels• Gather 2 million tweets from August

2011• Recall: actions are hashtags and

retweets

Remove infrequent actions and inactive users, leaving us with:

75,880 users32,030 actions

Data description

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 310

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Chart Title

Badges

artist

photographer

country music fan

book worm

Badge statistics

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Can we learn badges?

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Vegetarian badge

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Runner badge

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Hacker badge

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Manchester United badge

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Do all badges look this good?

No, but most do.

45wine lover

Over-generalized

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Overwhelmed

Ruby on Rails

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Can we just use the labels directly?

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Inferred Apple fanboy badge

Self-described Apple fanboys

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• Compare to labeled LDA [Ramage+ 2009]– LDA extension where each document is

labeled with multiple tags– One-to-one mapping between topics and tags– Document explained only by topics

associated with its tags

• Hold out random 10% of labels, treat as ground truth, and try to predict them

Comparative Analysis

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Rank of held-out labels be

tter

Better predictiveperformance

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bett

erBetter predictions for active

users

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Sparse badges

Apple fanboy (badges) Apple fanboy (l-lda)

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Approach Model Experiments Summary

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Leveraged how users describe themselves

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Leveraged how users describe themselves to build interpretable user features You behave like a

vegan hipster

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Empirically showed we can infer a user’s attributes from his behavior

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谢谢

What recourse do we have?

Collaborative filtering

Content-based filtering

Can we do better?

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Most vegans don’t label themselves as “vegan” on Twitter……but what about non-vegans?

“I drink too much and hate vegans.”