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You Make Pearson Cry #1: Stay Together for the Money December 11, 2006

Posted by Johan in Off Topic, Rants, You Make Pearson Cry.
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The British Conservative Party launched a report today, which inspired me to create a new feature for this blog: you make Pearson cry, named after the man who did the first work on correlation, and whom the Pearson correlation coefficient is named after. Of course, I have no idea what Pearson might have thought about inappropriate use of his measure of effect size. After all, the man was a eugenicist, for whom confusing correlation and causation is par for the course. It’s that very confusion which will be the topic of this feature.

The report seems to be quite wonderful in its blatant disregard for what might be inferred from a correlation. Case in point:

Iain Duncan Smith’s report for the Tories on poverty, found family splits caused social problems costing £20bn.” (BBC)

So, you’ve figured out that divorced parents have more social problems, and that their kids get into more trouble. So far so good. Next, you conclude that if they stayed together, you wouldn’t have a problem. Umm, no. There are a million other variables with also differ between people who have problems and people who don’t, and it seems a bit idiotic to believe that of all those, it isn’t a family history of poverty and social problems; it isn’t drug use; it isn’t screwing up school. No. Instead, marital status is the underlying cause of all these! So what do we do?

“Couples should be “encouraged to get together and stay together” – possibly with the help of changes to taxation to support marriage, Mr Cameron said” (BBC)

We buy them off. Clearly some of these couples that split up, thus causing, in essence, the downfall of the British Empire, would stay together for purposes of taxation. We all know how great it is when parents stay together for the kids. Now parents who don’t care about the kids can still stay together for the money, which is likely to result in everyone living happily ever after, according to Mr Cameron.

Just to be clear: this proposal is really looking out for the poor. It has absolutely nothing to do with the Conversative constituency being made up of married couples who like tax breaks.

Brain Voyager: Brain Tutor – Neuroimaging for Free December 9, 2006

Posted by Johan in Neuroscience, Raves.
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In my last post I discussed how some aspects of Psychology just aren’t well explained through long paragraphs of text. Neuroscience is certainly one example, where the location of each bit can seem more than a little abstract (which is closer to the side of the head, the medial frontal or the precentral gyrus?). A free application available for Mac, Windows and Linux comes to the rescue: Brain Voyager: Brain Tutor. The full-scale Brain Voyager program deals with visualising and analysing fMRI data. The Brain Tutor simply has one structural MRI image pre-loaded, and lets you zoom around it. It even highlights gyri, sulci, or lobes for you, as you click on them.

Unfortunately, Brain Tutor can be confusing to use at first, and its documentation is a bit lacking. So I wrote a guide to Brain Tutor. Hopefully it will prove useful. If you’ve never used Brain Tutor, there are some pictures of the application in action in the guide. Here is a sneak peek:

Understanding connectionism December 5, 2006

Posted by Johan in Connectionism, Neural Networks, Raves.
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Like many Psychologists, equations make me a little uneasy. So connectionist models are typically not my choice of reading, when I have a choice in the matter. This is a shame really, because these models tend to be extremely powerful: with a relatively simple model, complex phenomena can be explained in a framework that maps closely on to what is known about how the brain works.

Take McClelland’s model of memory*. Reading the original article is painful, yet, the model itself is not complicated, when presented in a different way. The Belgian Cognitive Science Research Unit has an extremely enlightening demonstration of the model, called a Tribute to Interactive Activation. Just click individual nodes of the model (to simulate activation), and see the associated nodes light up as well. Start clicking a few nodes (e.g., 40′s, married, college), and soon, one of the name nodes receives more total activation than the others. This is a pretty neat way of representating how the memory of one concept is evoked by the activation of related concepts.

This ties in with something I noticed during this term’s Perception module: a lot of these concepts are just not well explained in the traditional, academic journal style of writing. Reading something like van de Grind et al’s (2004) gains-equalisation model is quite painful. I could not grasp what was going on until I started drawing figures for myself… And I would most likely never have bothered with going that far unless the paper had carried so much promise in explaining storage of the motion after-effect, which was the topic of an assessed practical. Similar measures were necessary to process the wealth of research reviewed in Livingstone and Hubel’s (1988) paper on the perceptual properties of the magno- and parvocellular layers of the Lateral Geniculate Nucleus. No real structure emerges until you make a table and start listing the things that the article claims the different cells can and cannot do.

Some kinds of information are better conveyed through figures, animations; anything but sentences. It is a little curious that despite this, so many textbooks and articles rely almost exclusively on sheer text. Probably, the maths that so unsettle me have similarly enlightening effects on those who speak its language. Perhaps there is some truth in my girlfriend, the Biologist’s repeated, pointed remark that “you can’t be a proper scientist without knowing calculus.”

* McClelland, J.L. (1981). Retrieving general and specific information from stored knowledge of specifics. Proceedings of the Third Annual Meeting of the Cognitive Science Society, 170-172.

Neurosurgery webcasts at OR-Live December 1, 2006

Posted by Johan in Neuroscience.
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The Neurophilosopher posted a story which links to google video clip of a complete hemispherectomy – that is, removal of a hemisphere and the corpus callosum. This is plenty cool in itself. I found the originating website, called OR-live, and it turns out that they have a fairly large archive of neurosurgery videos. Unfortunately, they are in Realplayer format, but if you have the connection for it, or if you’re inclined to do some light hacking to save the file to your hard drive, these are well worth watching.

Personally, it mainly makes me happy I’m not a med student. fMRI images give me plenty enough detail, thank you very much. No need to go poking at the stuff.


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