Welcome to Derpica

You’ve probably seen the word “derp” floating around lately. You may wonder what it means … and why we seem to be living in Derpica.

I first saw the word “derp” on Twitter, where it usually appears in a context like this:

BlueTweepTwo: RedWingNut’s derp is strong. || RT .@BlueTweepOne RedWingNut: “IRS scandal will force Obama to resign.”

That is, BlueTweepOne tweeted a quote from RedWingNut: “IRS scandal will force Obama to resign.” BlueTweepTwo retweeted and added a comment: “RedWintNut’s derp is strong.”

(Continued Below)

This means RedWingNut is … what, exactly?

“A useful term for a concept that never had its own word”

Enter BusinessInsider‘s Josh Barro with an excellent explanation of what “derp” isn’t

“Derp” is a useful term for a concept that never had its own word. Since derp is on the rise, we need a term for it now more than ever.

[Gawker‘s Max] Read says “derp” is “a word for ‘stupidity.'” Not quite. All derp is stupid, but not everything that is stupid is derp.

… and explaining what “derp” is. The answer has to do with Bayes Theorem, which we explored last October in discussing Nate Silver’s The Theory and the Noise:

Finally, Silver’s most important point is that Bayes Theorem never gives you a “final answer.” It gives you an adjusted prediction, based on your Prior and the Signal and Noise in some new information … but when you get newer information, you have to update your prediction again.

Your previously-adjusted prediction becomes your new Prior, and you go through the same process – again and again – each time you get new relevant information.
[…]
We don’t have to stay stuck on our polar opposite views. Maybe you were right. Maybe I was right. Maybe we were both wrong. But if we apply Bayes Theorem together, we’ll both sneak up on the best new prediction we can find … until we get new information.

And that’s a good reason to hope.

Unless you’re facing derp.

“That twerp just herped a flerp of derp!”

Barro quotes Noah Pinion’s excellent discussion of derp:

How much does the evidence change your belief? That depends on three things. It depends on A) how different the evidence is from your prior, B) how strong the evidence is, and C) how strong your prior is.

What does it mean for a prior to be “strong”? It means you really, really believe something to be true. If your start off with a very strong prior, even solid evidence to the contrary won’t change your mind. In other words, your posterior will come directly from your prior. (And where do priors come from? On this, Bayesian theory is silent. Let’s assume they come directly from your … um … posterior.)
[…]
But here’s the thing: When those people keep broadcasting their priors to the world again and again after every new piece of evidence comes out, it gets very annoying. After every article comes out about a new solar technology breakthrough, or a new cost drop, they’ll just repeat “Solar will never be cost-competitive.” That is unhelpful and uninformative, since they’re just restating their priors over and over. Thus, it is annoying. Guys, we know what you think already.

English has no word for “the constant, repetitive reiteration of strong priors.” Yet it is a well-known phenomenon in the world of punditry, debate, and public affairs. On Twitter, we call it “derp.”

Pinion even adds some other terms:

(Also, the verb associated with “derp” is “herp”. It describes the action of coughing a large sticky mass of derp onto the internet in front of you. For example, to use it in a sentence: “That twerp just herped a flerp of derp!” A “flerp” is a unit I made up. It is the amount of derp that can be herped by one twerp. See?)

“OK, this is awesome”

Thus began Paul Krugman’s article yesterday on his debate with RedState‘s Erick Erickson. Erickson kicked things off by saying that New York-D.C. elitists don’t understand the plight of ordinary people, citing this example:

The rest of America is nervous about where their next meal and paycheck are coming from, how they are going to afford to bail their kids out of crumbling schools, and the price of a gallon of milk and loaf of bread that keep going up though Ben Bernanke tells them there is no inflation.

Dr. Krugman replied with actual data showing that the price of milk and bread, while rising or falling month-to-month, are about where they were in January 2009. That prompted this response from Erickson:

And if he hung around moms and dads with kids more often he’d hear a lot more real world complaining about bread, milk, and other grocery item prices going up while paychecks are staying the same. Not everything is academic or chartable and sometimes the accuracy of the chart isn’t as real to people as the perception they have that their grocery store bills are getting more expensive though their shopping habits haven’t changed.

As Barro notes in his excellent summary of the debate, it’s not surprising that ordinary people might not know that, as research shows that we tend to overestimate inflation. But here’s where we get back to derp. Even knowing that his facts are wrong, Erickson refuses to back down:

Seriously, Paul’s point is correct, but it is an issue of perception of people versus the reality of his chart. He can certainly go tell people milk prices haven’t gone up, but good luck getting them to believe him.

Erickson lives in Derpica, a place inhabited by people with unshakably strong priors. People who insist the price of milk and bread are soaring, even when data show that isn’t true. People who insist the IRS scandal will force President Obama to resign, even when evidence shows the only scandal is House Oversight Committee Chairman Darrell Issa’s abuse of the Inspector General investigation process. People who are immune to new information unless it confirms what they already believe.

Conservatives need to keep their followers convinced of demonstrably false beliefs. So pundits like Erickson repeat those false beliefs, and then say data “isn’t as real to people as the perception they have.”

He just herped a gigaflerp of derp.

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