cognitive science and more
cognitive science and more
A bit about pupil size, attention, and inhibition

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.
A beer coaster.A beer coaster.

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 that you don't need to look at something bright for your pupils to constrict. Just paying attention (without looking) is enough. In a way, when you pay attention to something, your pupils respond as if you were looking directly at it.

In a paper that just appeared in Journal of Vision, my coauthors and I studied this phenomenon in more detail. I'm very excited about this study, so I wanted to share the main result in a blog.

Our experiment was very simple. Participants kept their eyes fixated in the center of a display, and identified a target stimulus that appeared on the left or right side of the display. Just before the target appeared, there was a brief movement on the left or right side of the display. This movement was not relevant for the task (i.e. it did not predict the location or identity of the target), but participants were nevertheless unable to ignore it: Movement automatically attracts attention, whether you want it to or not.

So far, so just another good-old-fashioned cuing paradigm. But we added a little twist: Half of the display was bright, the other half was dark. Therefore, attention was sometimes drawn toward brightness (when the movement occurred on the bright side), and sometimes toward darkness. And because we know from previous studies that attention affects the pupillary light response, this brightness/darkness manipulation allowed us to study what happens to attention in this type of experiment.

A bit about our open-science Marie Curie project

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.

Is bright text on a dark background a good idea?

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?

Collaborating fish(es)

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:

Open-source software for science

This is a guest post for the Open Science Collaboration Blog. You can read the full post here.

A little more than three years ago I started working on OpenSesame, a free program for the easy development of experiments, mostly oriented at psychologists and neuroscientists. The first version of OpenSesame was the result of a weekend-long hacking sprint. By now, OpenSesame has grown into a substantial project, with a small team of core developers, tens of occasional contributors, and about 2500 active users.

Because of my work on OpenSesame, I've become increasingly interested in open-source software in general. How is it used? Who makes it? Who is crazy enough to invest time in developing a program, only to give it away for free? Well ... quite a few people, because open source is everywhere. Browsers like Firefox and Chrome. Operating systems like Ubuntu and Android. Programming languages like Python and R. Media players like VLC. These are all examples of open-source programs that many people use on a daily basis.

But what about specialized scientific software? More specifically: Which programs do experimental psychologists and neuroscientists use? Although this varies from person to person, a number of expensive, closed-source programs come to mind first: E-Prime, SPSS, MATLAB, Presentation, Brainvoyager, etc. Le psychonomist moyen is not really into open source.

Continue reading on the Open Science Collaboration blog!