Oxford University Press, 2011 (Paperback)

Conclusion From turbulent rivers to auto-catalytic chemical reactions. With the "Nature's Patterns" trilogy, Philip Ball gives us an eclectic, yet surprisingly coherent overview of all kinds of patterns that are found in nature. It's an interesting and challenging read, but perhaps a single book would have sufficed.

Why are honeycomb cells hexagonal? Why do spotted animals tend to have striped tails? And, for that matter, why are animal pelts so often spotted or striped, rather than endowed with, say, a rectangular grid? Why does Jupiter have a giant red spot?

The diversity of the issues that Philip Ball takes on in his trilogy on nature's patterns is overwhelming. Most of them cannot even be said to have much in common: Jupiter's red spot cannot be explained in the same way as the shape of a honeycomb cell. Yet, despite his eclectic subject matter, Philip Ball manages to tell a coherent story. One that goes far beyond stamp collecting of interesting factoids.

A recurring theme in the three books (Shapes, Flow, and Branches) that together form Nature's Patterns: A Tapestry in Three Parts is that many patterns are 'emergent properties'. Spotted and striped pelts do not necessarily provide the best possible camouflage, so they cannot be fully explained in Darwinian terms. Nor is it practical (even if perhaps theoretically possible) to explain such patterns in terms of the laws of physics. Instead, Ball argues, to explain why spots and stripes are so common, you need to …

When writing a scientific paper it is considered good style to convey an absolute and unrelenting trust in your own findings. So in many papers the discussion section starts with something like 'the present study is the first to conclusively show that (...)' or 'the results clearly show that (...)'.

I've written a few lines like that as well. But, tainted with hypocrisy, I actually find this style of writing a bit weird. It is no secret that cognitive science is a messy business, and that experimental data is seldom clear-cut. Most scientists, and certainly the good ones, are quite frank about this. So why the sudden attack of confidence when writing a paper?

Well... I don't know, and perhaps it is just a matter of style without any real reason. Fashion, in a sense. But it does strike me that this is a relatively new phenomenon, and that scientists in the past were much more equivocal in their writing. The quite recent past, even. Take, for example, Michael Posner, who wrote in the abstract of his seminal 1980 paper Orienting of Attention that '(...) the possibility is explored that (...)'. Or Giacomo Rizzolatti, of mirror neuron fame, who wrote back in 1987 that '(...) the hypothesis is proposed that postulates (...)'. Both of these sentences (which were of course cherry-picked for the occasion) convey a modest degree of belief in ones own theory and/ or findings: I believe in X, but I could be wrong.

I thought it would be cool to analyse the PubMed …

PubMed is a popular search engine for biomedical literature. It has lost a lot of ground to Google Scholar over the past few years, but for a long time it was the go-to scientific search engine for psychologists, neuroscientists, and the likes. And the cool thing is that, unlike Google Scholar, PubMed allows you to write scripts to automatically download enormous amounts of information.

Which is what I did over the weekend: I downloaded information about scientific articles. Names, authors, abstracts (summaries), journal titles, etc. And lots of it. I figured I would eventually get banned for abusing the PubMed service, but I didn't, and the end result is a database containing 257.535 articles published between 1950 and 2010 in 43 academic journals, broadly focused on neuroscience and cognitive psychology [1]. To the extent that PubMed has a complete index, this should include a large proportion of all articles published between those years in those journals.

So that's a lot of data!

I'm planning to write a series of blog posts, each time focusing on a different aspect of this data set. My main aim will be to understand the whole system academic publishing just a little bit better, and to see how it has evolved over the years. All the while keeping in mind, of course, that even these quarter of a million articles reflect just a tiny fraction of the total volume of scientific output. And a biased fraction at that, because the journals have been hand-picked …

I recently stumbled across a great video tutorial for the OpenSesame experiment builder. This video, created by Chris Longmore, shows how to build an experiment in which participants have to judge the gender of a (picture of a) cat. This is kind of goofy, but experiments of this kind have been conducted at least twice. Once by Quinn and colleagues, and once by Longmore himself. And, apparently, people are able to distinguish male cats from female cats. Barely, but still. (You can participate in an online version of the experiment here.)

Here's the video:

And, because I'm sure you're wondering, here are some pictures of cats split by their actual and perceived gender. It seems (to me) that people go largely by colour and size: Big, dark cats look male, whereas slender and lightly coloured cats are perceived as females.

References

The Chicken Head is a dance that was popularized by the video clip to Chingy's Right Thurr, which was a big hit back in 2003.

If you do the Chicken Head well, the flapping of your 'wings' makes you look a bit like a chicken. Another distinctly chicken-like aspect of the dance is that you need to keep your head more or less still, while swinging your body from side to side.

For this post I will elaborate a bit on this last point.

As you can see in the video above, chickens are remarkably good at keeping their head still while their body is moving. They are able to do this when someone else moves their body, as in the video, but also when they move themselves. This is why a chicken's head (or a pigeon's head, as in the video below) bobs back and forth during walking: The chicken keeps its head still with respect to the environment by moving it backwards to compensate for the forwards body movement. This continues until the head cannot move back any further, at which point it rapidly snaps forward, momentarily breaking the otherwise near perfect head stabilization (see note 1 below for a popular myth on head bobbing).

When you think of it, head stabilization is a remarkable feat: The gravitational (or vestibular) sense is required to keep the head up-right, regardless of the body's orientation. And you also need to take into account the position of the body parts relative …