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Let’s Disqus

Today I opened a Disqus forum on the blog. You can find the discussion threads at the end of every post. I also have added the forum to the previous posts, so that you can retroactively express your opinion.

It's about 6 months that I started writing, and I could have done this earlier (The Grand Locus is a fork of Nick Johnson's Bloggart, which includes support for Disqus), but I must confess that my tolerance for trolls is very low (there, that's one on the left). I hate having to search information in the middle of personal insults on the forums.

But then I started to be active on Cross Validated which is Stack Overflow's statistics spin-off. And it was a double surprise. I realized that Internet communities are not intrinsically dysfunctional, and I also realized that people of an extreme competence, who deserve academic respect, are part of these communities. And the awesome news is that some of them read this blog!

Anyway, the forum is now open and here are a couple of guidelines in case you don't feel like fooling around and try stuff.

  • To write or reply...

Focus on: multiple testing

With this post I inaugurate the focus on series, where I go much more in depth than usual. I could as well have called it the gory details, but focus on sounds more elegant. You might be in for a shock if you are more into easy reading, so the focus on is also here as a warning sign so that you can skip the post altogether if you are not interested in the detail. For those who are, this way please...

In my previous post I exposed the multiple testing problem. Every null hypothesis, true or false, has at least a 5% chance of being rejected (assuming you work at 95% confidence level). By testing the same hypothesis several times, you increase the chances that it will be rejected at least once, which introduces a bias because this one time is much more likely to be noticed, and then published. However, being aware of the illusion does not dissipate it. For this you need insight and statistical tools.

Fail-safe $(n)$ to measure publication bias

Suppose $(n)$ independent research teams test the same null hypothesis, which happens to be true — so not interesting. This means that the...

The most dangerous number

I have always been amazed by faith in statistics. The research community itself shakes in awe before the totems of statistics. One of its most powerful idols is the 5% level of significance. I never knew how it could access such a level of universality, but I can I venture a hypothesis. The first statistical tests, such as Student's t test were compiled in statistical tables that gave reference values for only a few levels of significance, typically 0.05, 0.01 and 0.001. This gave huge leverage to editors and especially peer-reviewers (famous for their abusive comments) to reject a scientific work on the ground that it is not even substantiated by the weakest level of significance available. The generation of scientists persecuted for showing p-values equal to 0.06 learned this bitter lesson, and taught it back when they came to the position of reviewer. It then took very little to transform a social punishment into the established truth that 0.06 is simply not significant.

And frankly, I think it was a good thing to enforce a minimum level of statistical reliability. The part I disagree with is the converse statement...

Is there a gene for alcoholism? (1)

This is usually the next thing I hear when I say that I am a geneticist. Behind this question and its variants lies a profound and natural interrogration, which could be phrased as "how much of me is the product of my genes?" I made a habit of not answering that question but instead, highlight its inaneness by lecturing people about genetics. So, for once, and exclusively on my blog, here is the tl;dr answer: no, there is not. Now comes the lecture about genetics.

I will start with mental retardation — unrelated with my opinion of those claims, really — and more precisely with the fragile X syndrome. James Watson, the co-discoverer of the structure of DNA and the pioneer of the Human Genome Project declared:

I think it was the first triumph of the Human Genome Project. With fragile X we've got just one protein missing, so it's a simple problem. So, you know, if I were going to work on something with the thought that I were going to solve it, oh boy, I'd work on fragile X.

In other words, there seems to be a gene for mental retardation. The incidence...

The chaos and the doubt

Probability is said to be born of the correspondence between Pierre de Fermat and Blaise Pascal, some time in the middle of the 17th century. Somewhat surprisingly, many texts retrace the history of the concept up until the 20th century; yet it has gone through major transformations since then. Probability always describes what we don't know about the world, but the focus has shifted from the world to what we don't know.

Henri Poincaré investigates in Science et Méthode (1908) why chance would ever happen in a deterministic world. Like most of his contemporaries, Poincaré believed in absolute determinism, there is no phenomenon without a cause, even though our limited minds may fail to understand or see it. He distinguishes two flavors of randomness, of which he gives examples.

If a cone stands on its point we know that it will fall but we do not know which way (...) A very small cause, which escapes us, determines a considerable effect that we can not but see, and then we say that this effect is due to chance.

And a little bit later he continues.

How do we represent a container filled with gas? Countless molecules...

The autistic computer

I was the shadow of the waxwing slain
By the false azure in the windowpane

What did Vladimir Nabokov see in the first verses of Pale Fire? Was it "weathered wood" or "polished ebony"? As a synesthete, his perception of words, letters and numbers was always tainted with a certain color. Synesthesia, the leak of a sensation into another, is a relatively rare condition. It was known to be more frequent among artists, such as the composer Alexander Scriabin or the painter David Hockney, but it turns out that it might also be frequent among autists. This might even be the reason that some of them have a savant syndrome (a phenomenon first popularized by the movie Rain Man).

One of those autistic savants, Daniel Tammet explains in the video below how he sees the world and how this allows him to carry out extraordinary intellectual tasks.

In his talk, Daniel Tammet explains how he performs a multiplication by analogical thinking. Because he sees a pattern in the numbers, he gives the problem another interpretation, another meaning, where the solution is effortless. This would happen at the level of the semantic representation (i.e. when the brains deciphers...

The geometry of style

This is it! I have been preparing this post for a very long time and I will finally tell you what is so special about IMDB user 2467618, also known as planktonrules. But first, let me take you back where we left off in this post series on IMDB reviews.

In the first post I analyzed the style of IMDB reviews to learn which features best predict the grade given to a movie (a kind of analysis known as feature extraction). Surprisingly, the puncutation and the length of the review are more informative than the vocabulary. Reviews that give a medium mark (i.e. around 5/10) are longer and thus contain more full stops and commas.

Why would reviewers spend more time on a movie rated 5/10 than on a movie rated 10/10? There is at least two possibilities, which are not mutually exclusive. Perhaps the absence of a strong emotional response (good or bad) makes the reviewer more descriptive. Alternatively, the reviewers who give extreme marks may not be the same as those who give medium marks. The underlying question is how much does the style of a single reviewer change with his/her...

Are you human?

On the Internet, nobody knows you're a dog.

This is the text of a famous cartoon by Peter Steiner that I reproduced below. This picture marked a turning point in the use of identity on the Internet, when it was realized that you don't have to tell the truth about yourself. The joke in the cartoon pushes it to the limit, as if you do not even have to be human. But is there anything else than humans on the Internet?

Actually yes. The Internet is full of robots or web bots. Those robots are not pieces of metal like Robby the robot. Instead, they are computer scripts that issue network requests and process the response without human intervention. How much of the world traffic those web bots represent is hard to estimate, but sources cited on Wikipedia mention that the vast majority of email is spam (usually sent by spambots), so it might be that humans issue a minority of requests on the Internet.

In my previous post I mentioned that computers do not understand humans. For the same reasons, it is sometimes difficult for a server to determine whether it is processing a request...

The elements of style

Let us continue this series of posts on IMDB reviews. In the previous post I used mutual information to identify a consistent trend in the reviews: very positive and very negative reviews are shorter than average reviews by about 2 sentences. But how can we give a full description of the style of reviews? And, what is style anyway?

Let's refer to the definition.

style /stīl/: A manner of doing something.

So style covers every feature of the text, from lexical (use of the vocabulary) to semantic (meaning attributed to expressions). The question of style has kept the field of Natural Language Processing (NLP) very busy because this is a strong indicator of the content of a text. What is it about? How reliable is it? Who is the author? However, most of the emphasis is on the syntax, because semantics is still a long and painful way ahead. Alan Turing, by his claim that a machine is able to think if it is able to communicate with humans in their natural languages (the Turing test), sparked a general interest for the question of language in the field of artificial intelligence. A bunch of chatting robots...

Did Sweden cheat at Eurovision?

In my previous post, I promised to go deeper into IMDB reviews, but I defer it until I deal with a more pressing issue.

Last Saturday was the Eurovision song contest. Somehow, my girlfriend managed to convinced me to sit through it (apologies to my fellow disincarnated academic researchers for such a treachery to our quest for knowledge).

Outside the epic performance of Ireland, already consecrated in the pantheon of memes, the show was plain boring. More specifically, it was redundant. Many songs were duplicates of each other and most were clear wannabes of successful artists (poor Amy, if you had seen what Italy did to you).

It was such a surprise, a shock I should say, that Sweden won the contest with the song Euphoria. Not that it was bad. Rather, that it was exactly like the songs we keep hearing every summer for more than 20 years. So, is this me getting old and not being able to recognize what's good music, or is there something fishy going on? I realized that the voting process is completely opaque and that nothing says that the IT counts the votes in a fair way. It would be...

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