A recent paper in PLoS Biology has caused a minor stir. In this paper, Pasley and colleagues show that you can find out which word a person has just heard by decoding activity in a specific part of the human brain. This is mind reading, in a sense. And it's therefore not surprising that some are talking about the Orwellian implications of this study, or speculate about the possibility of decoding inner speech in the same way.

But what did they Pasley and colleagues actually do? It's quite a technical paper, so you will have to forgive me if I have missed a few details. But the general idea behind the study is straightforward.

Pasley and colleagues recorded directly from the brain of human participants. Normally this is not possible, because intra-cranial recordings are highly invasive. You have to open up the skull in order to attach recording equipment to the brain. Few participants will agree to this, and even fewer ethical commissions will condone it. But sometimes, when a willing participant is about to undergo brain surgery (usually for a severe form of epilepsy), scientists get the unique opportunity to do this kind of experiment with humans.

The brain area that Pasley and colleagues recorded from was the posterior superior temporal gyrus. This area is traditionally thought of as a midway station in the transformation from low-level acoustic information (sounds without meaning attached to them) to conceptual representations (the meaning of words, concepts, etc.).

The neurons in this brain …

I just came across an inspiring blog post by the mathematician Tim Gowers. In this post, which I invite you to read, he calls for a boycott of Elsevier. I share his discontent and so, I hope, will you.

Elsevier is one of the largest academic publishers, and is notorious for charging extremely high prices. This places a considerable financial burden on publicly funded academic institutions, who are, for various reasons, practically forced to buy Elsevier content. Elsevier has also engaged in other dubious practices, such as actively supporting a bill against open access publishing.

Elsevier is not alone in this. In fact, not too long ago there was a similar outrage over price increases by the Nature Publishing Group. But, as Gower points out and as you can read in the overview by White and Creaser, Elsevier is quite simply the worst.

There is now a website, The Cost of Knowledge, which calls on scientists to declare publicly that they will not support Elsevier by publishing in or reviewing/ editing for any of the Elsevier journals. I must admit that, at first, I was a little hesitant to sign this, because preventing myself from publishing in Elsevier journals is not necessarily a booster for my (very young) career. But I have decided that I will sign nevertheless: There are plenty of good, open access alternatives in my branch of research: any of the PLoS journals, Journal of Vision, BioMed central, Journal of Eye Movement Research, to name but a …

The Great Bowerbird is a curious bird. The males spend most of their time building bowers, which are elaborate structures, constructed solely for attracting females. These loveshacks are decorated with stones (and sticks, bones, etc.) in a very specific way: Small stones are put near the entrance of the bower; Larger stones are put further away. When looking out from the inside of the bower, which is were the females stand during courtship, this arrangement leads to a striking distortion of perspective. You can see this in the image below (compare b to c). In a sense, the size gradient of the stones flattens the image, reducing the subjective perception of depth.

Photos from Kelley & Endler (2012) and Anderson (2012)

The male bowerbird is quite picky about this arrangement. If the size gradient is disturbed (by a biologist, for example), the males immediately restore it. But why? Since the purpose of the bower is to seduce females, it is tempting to speculate that the distorted perspective is aesthetically pleasing to female bowerbirds. Who, as mentioned above, tend to stand inside the bower as they watch the male perform his dance of seduction.

But there could be numerous other explanations. For example, the males could simply be too lazy to carry big stones all the way to the bower. Or something like that.

But no, it appears that the distorted perspective really is what matters. In a recent issue of Science, Kelley and Endler investigated what the perfect size gradient is …

The following illusion is a variation on the boogie-woogie illusion, described by Patrick Cavanagh and (yes, again!) Stuart Anstis. If you play the video and track the moving dot with your eyes, you will see that the edges of the diamond shape come to life. Specifically, the dots that make up the edges appear to travel along the lines. Kind of like the steps of an escalator.

So what might be going on here? I have to admit that my degree of belief in the explanation that I will outline here is modest. But that being said, here we go: Essentially, this illusion could be an instance of the aperture problem.

Imagine that you are looking through a hole, as in a in the figure below. Through this hole, you can see part of a bar, but not all of it. Now imagine that the bar moves, as in b, c, or d. Can you tell, based on what you can see through the hole, what the exact movement of the bar has been? No! As long as you cannot see the ends of the bar, all three forms of movement look the same.

So what do people perceive when presented with this type of ambiguous motion? Well, they tend to perceive a motion that is orthogonal to the length of the object (d). Perhaps we are biased to perceive orthogonal motion, because that's how objects generally move (do they, though?). Or perhaps it's because orthogonal motion is, in a …

I recently came across this awesome optical illusion, first described by Stuart Anstis. Two bars, one red and one blue, move horizontally across the display. If a specific type of background texture is present, the two rectangles appear to move in anti-phase: When the red rectangle moves quickly, the blue one grinds to a halt, and vice versa. This is illusionary, of course, and the effect is gone when the background texture is removed.

The two rectangles resemble a pair of stepping (or shuffling) feet, hence the name: the stepping feet illusion. (The effect is strongest for some people if you don't look directly at the rectangles.)

The explanation for this illusion appears to be fairly straightforward (but see [1]). And, as any good illusion, it provides some insight into how our visual system works.

The crux is that the illusion will not work with just any pair of colours: There must be a luminance difference. Put differently, one stimulus must be bright (the blue rectangle in this case) and the other must be dark (the red one). In addition, there must be a comparable luminance difference in the background, which is achieved here through a pattern of alternating light and dark bands.

Now, let's say that the front and hind edges of the stimuli are on a dark band, as in a) in the figure below. In this situation, there is little contrast between the side edges of the red stimulus and the background (both are dark). Because of …