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What's Wrong with OKCupid's Matching Algorithm

OKCupid is using the wrong mathematics to match potential dates together. But before I critique them, let me compliment them on what they’re doing right:

  • “Our” mutual score is the geometric average of your score of me, and my score of you.
  • They low-ball the match % until they have enough statistical confidence in the number of questions we’ve both answered.
  • Questions come from users as well as staff. So they avoid some potential blind spots. (crowdsourcing)
  • OKCupid prompts you with questions that have the greatest chance of distinguishing you as quickly as possible. (maximally separating hyperplanes) If OKC already knows you want your date to shower at least once a day, keep a clean room, and that picking food from the trashcan is unacceptable, it won’t ask if you prefer crustpunks or gutterpunks.
  • You don’t have to be the same as me for us to match. I get to specify what answers I want from you.
  • They use a logarithmic scale of importance. Logs are the natural way we perceive levels or categories of importance. (For example “categories” of how big a war was, emerge naturally when you take the log of number of deaths.)
  • It’s simple. At least they’re not using a non-linear Bayesian splitting tree didactogram or some other hunky machine-learning jiu jitsu.

But, there’s still room for improvement. Particularly the following critique, originally made by Becky Russoniello. Currently, OKCupid is set up to award high scores just for being not-a-terrible match. That’s bad.

HOW MATCH PERCENTAGES WORK NOW

To show why I need to first detail how your score of me is calculated:

  1. You answer questions like, “Is homosexuality a sin?” Your answer consists of: (a) what you think, (b) what answer/s are acceptable for me to give, and © how important it is for me to get this question “right” per your definition.
  2. The question’s importance draws from {Mandatory, Very Important, Somewhat Important, A Little Important, Irrelevant} which biject to the numbers {250, 50, 10, 1, 0}.
  3. If I get a Very Important question “right”, I get 50/50 points, and if I get a Very Important question “wrong”, I get 0/50 points. If I haven’t answered the Very Important question, I get 0/0 points – neither penalised nor rewarded.

For more details, see their FAAAQ.

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THE PROBLEM

Here’s the important flaw: the denominator grows as long as we’ve answered the same question. In practice, the Mandatory questions both

  1. crowd out more interesting differentiators, and
  2. inflate the scores of people who merely have tolerable political views.

To demonstrate this, I’ll share some of the Mandatory questions from my own OKCupid profile.

  • Do you think homosexuality is a sin?
  • How often are you open with your feelings? (can’t be Rarely or Never)
  • Would it bother you if your boss was minority, female, or gay?
  • Would you write your child’s college entry essay?
  • What volume level do you prefer when listening to music? (can’t be “I prefer not to listen to music”)
  • Would you try to control your mate with threats of suicide?
  • Gay marriage – should it be legal?
  • Are you married, engaged to be married, or in a relationship that you believe will lead to marriage?
  • How important to you is a match’s sense of humor? (can’t be Not Important)
  • Would the world be a better place if people with low IQ’s were not allowed to reproduce?

Some other doozies which I might wrongly make Mandatory include:

  • Which is bigger? The Earth, or the Sun?
  • How many continents are there?
  • Do you consider astrology to be a legitimate science?

The problem with all of these filters, is that I mean them to act only in a negative direction. (Could I call them “quasi-filters”?)

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NON-TERRIBLE ≠ GOOD

In other words, someone doesn’t become a great potential match simply because they’re not

  • a bigot,
  • a cheat,
  • a eugenicist,
  • or a depressive manipulative.

You need to receive those check-marks just to get to zero with me. You also need to be not-married-to-someone-else. That doesn’t win you plus points, it’s just a requirement. But under the current OKCupid schema, you do win 250/250 from me for simply being available. Oops.

Likewise, knowing basic facts from grade-school seems, like, uh, necessary. But, even if somebody thinks there are 6 or 8 continents, do you really think you won’t be able to tell once they message you?

Few people will be culled by the Continents question, and if you make 10 such easy questions Mandatory, then everybody else will start with 2500/2500 points – so the rest of your match questions will barely distinguish one from the other. Even the Very Important questions (50 points apiece) will only budge the score a little below a default of 100%. And the Somewhat Important questions, which tend to be the more discriminative ones, are mowed down by the juggernaught of Easy Questions.

EDIT (23 NOV): According to the comments, the number of continents is not a universal fact, but rather varies from culture to culture (and within cultures). So that’s a really terrible question to make Mandatory! I should have said above Few people will be culled by asking whether the Earth is bigger than the sun, and if you make 10 such easy questions Mandatory, then everybody else will start with 2500/2500 points.

OKCupid asks other, more useful questions, like:

  • Are you annoyed by people who are super logical?
  • Do you like abstract art?
  • Do you spend more money on clothes, or food?
  • Could you tolerate a ___________________ [my political / religious views] ?
  • Do you like dogs?

which would actually distinguish among potential dates for me. Let’s face it: I write a blog about mathematics, so someone who is annoyed by super logical people is probably going to dislike me. And, I like abstract art. Maybe we could go to a gala for our first date.

Although everyone knows there are 7 continents the Sun is bigger than the Earth, not everyone is bothered by “logical” personalities. So those questions better sort the available dates.

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SPAMMABLE

The worst side effect of the current scoring system, is that a spammer could easily answer only the questions with obvious answers (basic facts and display of non-bigotry) and get a decently high match percentage with a lot of people. At which point, the spammer uploads a picture of an attractive guy/girl, writes some generic profile text, and scams away.

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THEY CAN MAKE THE SYSTEM BETTER

I think a better model oft how people evaluate potential dates can be found within economics. Specifically, Kahneman & Tversky’s Prospect Theory:

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The main lessons I draw from prospect theory, as a theory of psychology, are:

  1. We evaluate things based on a reference point (“zero”).
  2. Small perceived negatives are twice as bad, as small perceived positives are good (“local kink at zero”).
  3. Really bad or really good, we lose our ability to coherently measure how far from zero (“log-like at great distances”).

How does P.T. apply to dating and OKCupid?

Bigots, cheats, eugenicists, and depressive manipulatives are way off in negative land. I’m not even interested in meeting them. I don’t care whether OKC gives them a 0% or a 10%, because those are effectively the same to me: ignore. I only need OKCupid to accurately score people who are somewhere north of my reference point.

  • What if the scoring system simply binned everyone below 50%? They could all be labelled “non-match” and then twice as many numbers would be available to grade the remaining candidates.

    That’s a mathematically good idea, but doesn’t address the issue of dilution. And, it seems to ignore an aspect of “numbers psychology”: people like using only the upper half of the scale. Think about how people use the hotness scale: they would never be comfortable dating a 4.
  • What if OKCupid revamped their whole framework along the lines of Prospect Theory? Try to establish a reference point, do some research into psychology papers that bear on the topic, and so on.

    Well, it might be cool. But that’s a lot of work, and OKC is already successful. Big changes alienate users.

Here’s the simplest solution I can think of – which requires no UI changes and no research. In fact an OKC developer should only need to amend one line of code.

  • Mandatory questions can only give out negative points for answering wrong. No plus points for right answers to Mandatory.

Mathematically this is ugly because you introduce a discontinuity – but, so what? I think this is what the broad majority of people mean when they say something is mandatory. If you have a mandatory employee meeting, do people get a bonus for showing up? Does HM Revenue pat you on the back for paying tax?

In the eloquent phrasing of Chris Rock:

If OKC ends out giving some negative (or I guess imaginary, under the square root from the geometric average) scores, so what? I was ignoring everybody under 60% anyway.

YOU CAN MAKE YOUR SCORES BETTER

If you use OKCupid, there is a way to improve your matches even if they never change their matching algorithm:

  • Lower the importance of questions with obvious answers. I bet you won’t start matching with people who believe the Earth is larger than the Sun. And you will pick up extra precision in matches with other people.
  • Even if something is mandatory for you to date someone, don’t use the Mandatory category like that. Maybe you can have a few mandatory questions, but overall it just dilutes the scoring.
Diddy Punches Drake For Flirting With Cassie?

Diddy Punches Drake For Flirting With Cassie?

Diddy

Punches

Drake

For Flirting With

Cassie

?

(News n Music) UPDATE: Drake allegedly dislocated his arm. There are two versions to this story. One is that Diddy dislocated the arm in the fracas with Drizzy, but there is another rumor side. That is Drake dislocated his shoulder running away from Diddy and ran into a door, dislocating his arm from his shoulder. Wild!

There’s a lot going on in…

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Pandemonium Breaks Out At RNC As Trump Delegates Squash NeverTrumpers (Video)
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Pandemonium broke out on the floor of the Republican National Convention today as ten states attempted to introduce a resolution to release delegates from their pledges on the first vote.

After a voice vote was called, the chair called it for the “Ayes” despite the fact that there was absolutely no consensus on the floor for the motion. A roll-call vote was refused, which led Mike Lee and Ken Cuccinelli to protest loudly, but to no avail.

The Iowa, Colorado and Virginia delegations then left the convention floor in protest.

TPM:

Trump foes said they had the signatures of a majority of the delegates from nine delegations to force a roll call vote on the convention’s rules. However, when it became time to approve the rules, the officials presiding said that the three of those delegations had withdrawn their petition, and the rules were approved in a voice vote.

The scene on the floor was chaotic when the vote on the convention’s rules was called. The anti-Trump delegates, many of them clustered around the Virginia delegation, began chanting “Dump Trump,” only to be met by chants of “USA, USA.”

Sen. Mike Lee (R-UT) made a motion for a roll call vote, but it was announced that the movement had lost the three of the nine delegations it needed to force a vote.

Senator Lee was ranting, too:

read more

scientificamerican.com
Republican Platform Rejects Paris Climate Agreement
Renewable energy cut, price on carbon opposed ...
By Evan Lehmann,ClimateWire

Manipulated Fools and Idiots They Are - Phroyd

CLEVELAND—Christian Republicans promoted a transition to clean energy here last night, about an hour after GOP delegates approved a party platform that disavows aggressive action on climate change and downplays renewable energy.

The contrast isn’t new, said Angel Garcia, the national outreach director for Young Conservatives for Energy Reform, a group connected to the Christian Coalition of America. He and other organizers say they’re appealing to millennial party activists to support policies like long-term tax credits for wind and solar power, a national renewable portfolio standard and updated state laws that reward the use of distributed energy.

“We have to reach them,” Garcia said, “because they’ll be on the platform committee” in the future.

Current delegates came to a different conclusion.

The platform approved by a voice vote yesterday evening doesn’t explicitly question the science behind climate change. But it calls for reduced funding for renewable energy and international adaptation programs, and it seeks an end to the global agreement reached in Paris late year to cut greenhouse gas emissions worldwide.

The 66-page document also rejects the idea of an economywide carbon price, drawing a sharp contrast with drafts of the Democratic platform, which endorses that policy.

“We oppose any carbon tax,” the GOP platform says. “It would increase energy prices across the board, hitting hardest at the families who are already struggling to pay their bills in the Democrats’ no-growth economy.”

Instead, it urges private investors to develop carbon capture and sequestration technology.

‘FAR FROM’ A PRESSING NATIONAL SECURITY ISSUE

The platform also warns that if Donald Trump wins the presidential election, he would reorient the government’s approach to analyzing climate change. The document does not outwardly reject the underlying science behind global warming, but it does question its accuracy.

“Information concerning a changing climate, especially projections into the long-range future, must be based on dispassionate analysis of hard data,” it says. “We will enforce that standard throughout the executive branch, among civil servants and presidential appointees alike.”

Republicans also downplayed the role of climate change on national security, a topic that Young Conservatives for Energy Reform has focused on as a key challenge. The group regularly asks military generals to talk to members of the armed forces about the risks of running fuel convoys in war zones and the human costs of defending foreign oil fields.

“Climate change is far from this nation’s most pressing national security issue,” the platform reads. “This is the triumph of extremism over common sense, and Congress must stop it.”

It also calls for an end to U.S. involvement with the United Nations on climate issues, including the United States’ involvement with the more than 190 nations that negotiated the Paris Agreement.

“We reject the agendas of both the Kyoto Protocol and the Paris Agreement, which represent only the personal commitments of their signatories,” the document reads, adding that those deals are not binding.

It also calls for an “immediate” halt to U.S. funding for the U.N. Framework Convention on Climate Change, because the group granted membership to the Palestinians “as a state.” It cites a 1994 law, the Foreign Relations Authorization Act, that it says bars such funding. Providing additional money, it says, would be “illegal.”

The platform prioritizes fossil fuels, but it also gives a nod to renewable energy, as long as it’s affordable without taxpayer support.

“We support the development of all forms of energy that are marketable in a free economy without subsides, including coal, oil, natural gas, nuclear power, and hydropower,” it says. “We encourage the cost-effective development of renewable energy sources—wind, solar, biomass, biofuel, geothermal, and tidal energy—by private capital.”

Michele Combs, chairwoman of Young Conservatives for Energy Reform, said she believes the platform is not representative of the Republican Party’s views on clean energy policy.

“Even though it’s not represented that well in the platform, we think there’s a lot of support in the party,” she said, pointing to polls that show millennials see it as a “value” issue, similar to family and marriage issues seen as important by older party members.

“It’s not a taboo issue anymore,” Combs said.

Phroyd

On Wednesday, lawmakers in Utah voted to approve a bill that would make it legal for firefighters or law enforcement to shoot down, spoof, or otherwise disable drones found flying over airspace that the Federal Aviation Administration (FAA) puts under temporary restriction due to wildfire.

The bill was passed after a small drone flying over a fire 300 miles south of Salt Lake City forced firefighters to ground aircraft. Utah’s governor, Gary Herbert, has said that the fire expanded and became more expensive to control after the drone incident. Herbert is expected to sign the bill in the coming days.

Evan Vickers, the Utah senator that co-sponsored the bill, said that firefighters and police would be allowed to shoot a drone down, but he added that they’d probably use technology to jam signals sent to a drone and bring it down that way. (You can see a video of that kind of solution here.) “The redneck in me [says] to shoot the damn thing,” the Republican senator said to the Salt Lake Tribune. “But there are much more humane ways to do that,” he added.