Tens of thousands of psychology students have spent hundreds of thousands of hours in stuffy little lab cubicles doing visual-search experiments. They have searched for diamonds among squares, red lines among green crosses, smileys among frowneys, and so on. You would think that by now every conceivable visual-search experiment has been done. But no, there's still cool stuff left.

In a study that just appeared in Journal of Vision, Erik van der Burg and his colleagues used a genetic algorithm to breed the best visual-search display. That is, they used evolution through 'natural' selection to create a display in which a target object was super easy to find. The results are a little surprising, which makes this experiment extra cool.

Natural selection applied to visual-search displays. The fittest displays from generation 1 are crossbred to create the displays from generation 2. The target is the horizontal red line segment in the center.

Van der Burg and colleagues started with random displays that consisted of tilted red, green, and blue line segments. There was always one horizontal red line segment: the target. Participants had to find the target and indicate whether or not there was a small gap in it. The (r)evolutionary aspect of their experiment was that each display had a fitness, which simply corresponded to the speed with which participants found the target. Next, they used the three fittest displays to create a second generation of displays, which were random mixtures of their fit parents, with a little …

Let's try a little trick.

1. Take a piece of cardboard and punch a small hole in it, no bigger than say two millimeters. If you're in a bar—this is one of those bar tricks—a beer coaster will do just fine.
2. Cover your right eye with the piece of cardboard so that you can see through the hole. Make sure that no light gets through, except for through the hole.
3. Cover your left eye with your hand. Make sure that no light gets through at all.
4. Now uncover your left eye and watch what happens to the hole: It shrinks!
5. Now recover your left eye with your hand, and watch the hole become bigger again.

This trick allows you to see your own pupillary light response. When you remove your hand from your left eye, the light that suddenly enters the eye causes your pupils to constrict. (Your right pupil as well as your left, because pupils always act together). And this, in turn, causes the little hole to appear smaller. In other words, the apparent size of the hole directly reflects the size of your pupil! (If you're brave you can try to figure out the optics behind this effect. It took me a while.)

All of this was just an elaborate introduction to tell you what you already know: Pupils respond to light. Brightness causes pupils to constrict, and darkness causes pupils to dilate. But what you may not know (unless you read my previous post) is …

This is my first week as a Marie Sklodowska-Curie fellow. Exciting! Marie Curie fellowships are post-doctoral grants from the European Commision. They give young(ish) researchers like me the opportunity to focus full time on research for two years. Being a Marie Curie fellow is a good thing in every way, so I’m thrilled to finally start!

I will blog occasionally about the project. Most will be about the research itself, but in this first post I want to write a bit about how we are going to approach this project. (“We” refers also to Françoise Vitu, senior researcher of the project, and other collaborators.) To use a heavily overused buzzterm, this is going to be an open-science project.

An actress performing Marie Curie. The left-most badges have been designed by the Center for Open Science. The right-most badge is the officious open-access logo, designed by PLoS.

So what does this mean? The guiding principle is that all scientific output will be made publicly available. This may sound obvious (why do research if you’re not going to make the results available?), but it’s not typical of today’s research. Traditionally, scientific output consists solely of papers that are published in academic subscription journals. The data behind these papers is never shared. And the papers themselves are only accessible to a small group of people with journal subscriptions: i.e. other researchers, but not the taxpayers who paid for the research, nor clinicians who might benefit from the …

Right now you’re reading dark text on a bright background. This is called a positive-polarity display. Bright text on a dark background, like this, has a negative polarity. Positive polarity is much more common than negative polarity. Microsoft Word uses dark-on-bright text. This website uses it. And books use it, of course.

But a minority of people prefer it the other way around: bright-on-dark text. Negative polarity is particularly popular among software developers. For example, Atom is a programming editor that is developed by GitHub, the hippest of all hipster programmer communities. And Atom uses bright-on-dark text by default. Another example is OpenSesame, an editor for psychological experiments that I develop myself. By default, the editor component in OpenSesame uses negative polarity as well.

Examples of positive-polarity displays (left, dark-on-bright text), and negative-polarity displays (right, bright-on-dark) text.

So we have the nerds on one side, preferring bright-on-dark text, and the rest of the world on the other side, preferring good-old-fashioned dark-on-bright. So who’s right? Is this only a matter of taste? Or is one polarity really better than the other?

Well … There is a phenomenon called the positive-polarity advantage, which, as you might guess, refers to the fact that dark-on-bright text is better. In other words, Microsoft Word got it right, and GitHub and I got it wrong. But in what sense is positive polarity better? And why is it better?

One way to asses how well people can read text is through proofreading. In a proofreading experiment …

I stumbled across an interesting paper by Bshary and colleagues about collaboration between fishes¹. The study is already a few years old (see a recent follow up). But, new or not, collaborating fishes are always cute and worth writing about.

The fishes in question are the roving coralgrouper and the giant moray. Both are hunters, but their hunting styles differ. The grouper hunts for prey in the open water. To escape from the grouper, fishes tend to hide in the coral reefs, in small crevices where the grouper cannot reach. In contrast, the moray hunts by slithering through the reefs and capturing smaller fishes that hide in the reef’s crevices. To escape from the moray, fishes swim out into the open water. The potential for collaboration is clear: If the grouper and moray would hunt together, there would be nowhere to hide. They would make a deadly team indeed.

And they do hunt together. I tend to be skeptical of claims like this, which (to me) seem extraordinary. But Bshary and colleagues show quite convincingly that some form of collaboration must be going on. It works as follows: When the grouper is hungry, it actively seeks out a nearby moray and shakes its head to signal its intention to hunt. Most of the time, the moray responds by following the grouper. And they’re off–Swimming side by side and hunting. You can see this in the video below:

What I like about Bshary and colleague’s paper …