How Cambridge Analytica’s Facebook targeting model really worked • Hacker News Board

Re: How Cambridge Analytica’s Facebook targeting model really worked

#41

Post by etiam » Fri, Mar 30, 2018, 10:04 PM UTC

Spoiler warning. Article punchline ahead.

"The whole point of a dimension reduction model is to mathematically represent the data in simpler form. It’s as if Cambridge Analytica took a very high-resolution photograph, resized it to be smaller, and then deleted the original. The photo still exists — and as long as Cambridge Analytica’s models exist, the data effectively does too."

That's an eloquent piece of explanation of a very important point. And apropos the discussion about privacy legislation, it's also going to be a very interesting point. Will the Cambridge Analyticas of the world be able to claim they have held on to no personal data, when strictly speaking the raw data has indeed been deleted after being used to create a derivative work that can for all important purposes be used to recreate the original? Assuming I find out I'm being profiled and demand to have my data removed, will society grant me rights to have derivative forms removed or adjusted too? I'm somewhat pessimistic that legal hairsplitting about matters like these will make enforcement very difficult.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#42

Post by codezero » Fri, Mar 30, 2018, 10:05 PM UTC

godelski wrote: post #4

> has revealed that his method worked much like the one Netflix uses to recommend movies. I'm not sure this is the model you want to emulate. The suggestions are terrible and continually getting worse.

Are you saying all of Netflix suggestions are getting worse? How are you measuring that?

Or are you saying your netflix suggestions are getting worse?

Mine are pretty good and have held steady for a while, at least in terms of my own preferences, though I also am probably using it a little less as I've got Prime and Hulu now as well, so there's probably less times I'm randomly searching through Netflix and finding nothing.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#43

Post by r00fus » Fri, Mar 30, 2018, 10:05 PM UTC

emodendroket wrote: post #20

daenz wrote: post #3

Am I understanding this correctly? Facebook user data (likes/profile info) was scraped to produce low-dimension feature vectors for users (similar to word2vec). These feature vectors were then run through some ML model to predict...what exactly? Targetability for effective political ads?

It seems like the purpose was narrowly tailoring messages, which is something political campaigns are really keen to do now (Obama's campaign was kind of a trailblazer here, right?).

No it was Hillary's campaign in 2008 that was big on "microtargeting".

ie, moving beyond "soccer moms" or "defense dads" but "soccer moms with one kid and expensive tastes".

Re: How Cambridge Analytica’s Facebook targeting model really worked

#44

Post by jacquesm » Fri, Mar 30, 2018, 10:05 PM UTC

emodendroket wrote: post #39

jacquesm wrote: post #37

Earlier quoted context omitted.

Yes, that pretty much confirms what I wrote above. Your point being? Please read the article and compare what we know about Cambridge Analytica vs what the Obama campaign did, it is comparing snipers with someone setting off fireworks.

Look, I don't think anyone can realistically doubt that Obama's campaign was the first to effectively slice-and-dice the electorate and use social media to target them. You're arguing against a much more expansive claim than I'm making.

You used the word 'narrowly', and in the context of a post about Cambridge Analytica that word has a pretty specific meaning.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#45

Post by [deleted] » Fri, Mar 30, 2018, 10:05 PM UTC

godelski wrote: post #4

> has revealed that his method worked much like the one Netflix uses to recommend movies. I'm not sure this is the model you want to emulate. The suggestions are terrible and continually getting worse.

[deleted]

Re: How Cambridge Analytica’s Facebook targeting model really worked

#46

Post by danso » Fri, Mar 30, 2018, 10:06 PM UTC

dazc wrote: post #27

danso wrote: post #16

Earlier quoted context omitted.

OTOH, that you even chose to watch a movie is a sign that you are interested in the genre. Just because I abruptly stopped watching “Star Trek IX”, doesn’t mean that I have abandoned the sci-fi genre or even Star Trek

I have a friend who shares my account since I stay with him when I am in the UK. It isn't worth the effort to have two profiles. So, he likes horror movies and will watch any horror regardless of any signal that it's going to be poor. You can look at the viewing history and see he rarely goes beyond 5 minutes of watching any of them. I watch Netflix regularly throughout the year, he watches in phases that last a week…

I’m confused — you honestly expect Netflix’s model to have figured out that your profile is actually 2 people based on what you believe to be regular and obvious cyclical patterns? I would have to imagine that this is a relative edge case for Netflix, and there is no obvious answer for what to do with someone who mostly likes drama but for some reason, goes on a periodic horror binge.

I assume that Netflix’s model has the premise that profiles aren’t in fact, very easy to create. I have separate profiles for my parents, as well as a test profile to see what happens when a user only seems to like the “Human Centipede” trilogy.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#47

Post by downandout » Fri, Mar 30, 2018, 10:09 PM UTC

lordnacho wrote: post #10

Finally, I was waiting for someone to talk about the model itself. It makes sense that SVD or something like it (PCA, co-occurrence, etc) would be used. But I also wonder what exactly you are going to do with the predictions. What exactly do you show to someone to make them more likely to go and vote if they are inclined to vote your way, or make them stay at home otherwise? Is there evidence that whatever you're sho…

> I don't know how effective it is, I'd like to learn more. But I smell the possibility that these CA type firms are simply selling snakeoil to desperate political activists.

According to the article:

"The accuracy he claims suggests it works about as well as established voter-targeting methods based on demographics like race, age, and gender....the digital modeling Cambridge Analytica used was hardly the virtual crystal ball a few have claimed."

It's pretty clear that they were selling snakeoil. In fact, the use of CA wasn't particularly helpful to anyone [1]...hiring them was just a prerequisite for obtaining campaign contributions from the Mercer family, who had put up the money behind CA [2].

[1] http://www.businessinsider.com/cambridge-analytica-facebook-...

[2] https://twitter.com/kenvogel/status/975756418128187393

Re: How Cambridge Analytica’s Facebook targeting model really worked

#48

Post by icelancer » Fri, Mar 30, 2018, 10:12 PM UTC

metaobject wrote: post #17

mattmanser wrote: post #14

Earlier quoted context omitted.

How do you test anything? There's only one vote, you can't iterate.

Maybe with polling?

Data is terrible, especially for polarizing candidates like Trump. People simply lie in public about not voting for him, afraid of backlash that they will receive.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#49

Post by godelski » Fri, Mar 30, 2018, 10:14 PM UTC

danso wrote: post #46

dazc wrote: post #27

Earlier quoted context omitted.

I have a friend who shares my account since I stay with him when I am in the UK. It isn't worth the effort to have two profiles. So, he likes horror movies and will watch any horror regardless of any signal that it's going to be poor. You can look at the viewing history and see he rarely goes beyond 5 minutes of watching any of them. I watch Netflix regularly throughout the year, he watches in phases that last a week…

I’m confused — you honestly expect Netflix’s model to have figured out that your profile is actually 2 people based on what you believe to be regular and obvious cyclical patterns? I would have to imagine that this is a relative edge case for Netflix, and there is no obvious answer for what to do with someone who mostly likes drama but for some reason, goes on a periodic horror binge. I assume that Netflix’s model ha…

> as a test profile to see what happens when a user only seems to like the “Human Centipede” trilogy.

And? You can't just leave us hanging on that.

Re: How Cambridge Analytica’s Facebook targeting model really worked

#50

Post by iagovar » Fri, Mar 30, 2018, 10:15 PM UTC

emodendroket wrote: post #19

I am really puzzled by the Cambridge Analytica scandal. It's not particularly savory, but is there something happening here that it wasn't basically already known about how Facebook worked? By the protests of their own executive, the system was working as designed, and at worst Cambridge Analytica misled them about how they intended to use the data, right? There was no actual security breach here, as far as I can und…

No. I know at least one political consultancy that does a similar work in Spain, although I only know they work with data, use micro targeting and is run by a sociologist.