'Open access' is somewhat of a buzzword within academia. But unfortunately the term is widely misunderstood. All too often, the label 'open access' is used to refer to any content that can be accessed online for free. By this (incorrect) definition, most websites would be open access, because they offer content that you can read (or watch, listen to, etc.) for free. But you are usually not allowed to reproduce that content, or to sell it, modify it, etc. The only thing that you, as a consumer, are allowed to do is view the website right then and there, for as long as the owner of the website permits you.

This may be free of charge. It may even be a nice gesture. But it is not open access.

The definition of 'open access' is still evolving, but by consensus a number of conditions need to be satisfied for it to apply. In PLoS Biology, Michael Carroll gives us the following list:

Full open access content is

• Easily accessible online
• Available to anyone free of charge
• Available for re-use without restriction except that attribution be given to the source.

No one of these alone qualifies content for an open access label.

The paper by Carroll satisfies these criteria. I downloaded it for free. I am allowed to reproduce and redistribute the paper in it's entirety (here it is). And so are you. I didn't need Carroll's permission to upload his paper. And I do not (have to) care if he …

OpenSesame 0.26 Earnest Einstein, the next version of the graphical experiment builder, will be released soon! For those eager to test drive the next version, pre-release packages are available. You are encouraged to report bugs on the forum.

• Download pre-release packages (choose latest)

For this release, the focus is on bug-fixes, improved stability, and adding polish to the user interface. I expect 0.26 to be the best, most stable release of OpenSesame yet! Also, I'm glad to say that OpenSesame is rapidly becoming a collaborative effort. Special thanks go out to Daniel Schreij, for help in many areas, and Edwin Dalmaijer, for building the Python portable packages.

In the animation below, you can see a ring of four faces gradually morphing between Leighton Meester and Natalie Portman. If you keep your eyes fixated on the green cross in the center, you will notice that the morphing is quite difficult to see—but only when the faces are moving. If you match the movement with your eyes, or if the faces stop moving, you can clearly see the morphing happening.

This illusion was presented twice, in different guises, in the finale of last year's vision sciences illusion contest. Once by Jordan Suchow and George Alvarez, who ended up winning the contest. And once by Rob van Lier and Arnon Koning. So this illusion may not be entirely original, but it is certainly the most aesthetically pleasing rendition out there!

So what's going on here? Previously, I explained this phenomenon in terms of retinal motion. When the faces move, they slide across your retina (the light sensitive part of your eye), at least if you keep your eyes still. So the same face will be 'seen' successively by different parts of your retina. And because the organization of the retina is roughly preserved in visual areas of the brain, the same face will be successively processed by slightly different (sub)areas of your brain. According to the 'retinal motion' explanation, these different brain areas do not communicate effectively enough for changes to be detected. At least not if they are small and gradual.

But, as it turns out, this …

We all see things that are not there, every now and again.

Particularly things that are on our mind. For example, if you're thinking about someone, you're increasingly likely to see, or think to have seen, that someone out on the street. This is because our perception is biased by our expectations. Put differently, we try to fit what we see into mental templates.

A recent study by Smith and colleagues shows this in a new way, which I think is kind of cool. In this study, participants watched patches of completely random noise, like static on television. But the participants were tricked. (Yes, they keep falling for it.) They were told that on half of the trials a face was hidden in the noise. And they were instructed to indicate on every trial whether they had seen a face or not.

The analysis that Smith and colleagues performed was quite simple. They took the average of the patches of noise on which the participants indicated that they had seen a face, and subtracted from this the average of the non-face patches. If the participants had just been randomly pressing keys, this procedure would have led to a uniformly black image. After all, the average of lots of noisy patches is uniformly grey. And grey minus grey is black.

But this is not what happened! Out of the noise emerged clear (well, let's say reasonably clear) outlines of faces. Apparently, the participants tried to match their template of what a …

In the animation below, it appears as though Mario is jumping vertically and the Koopa shell is gliding horizontally. But actually, as you can clearly see when the background stops moving, Mario and the shell both move in circles!

(This illusion is a variation on Stuart Anstis' Flying Bugs illusion.)

So what's going on here? The first thing to note is that, although Mario and the shell are following a similar circular trajectory, they are in antiphase. Which is just a fancy way of saying that when Mario is at 12 o'clock, the shell is at 6 o'clock. The background image also follows a circular trajectory. But it goes clockwise, so the rotation of the background is opposite to that of Mario and the shell.

The crux of the illusion is that the rotations of the three elements (Mario, the shell, and the background) are aligned in a very specific way. The horizontal component of the background motion is the same as Mario's: When the background moves to the right, so does Mario. Mario's horizontal movement is therefore cancelled out, and consequently Mario appears to move only vertically. Conversely, the vertical component of the background motion is matched to that of the shell. Therefore, the shell appears to move only horizontally.

This illusion is a very salient demonstration of how we use background information to make judgements about positions and movement. We don't perceive the actual movement of Mario and the shell, we perceive their movement relative to the background …