Suchow and Alvarez report a very compelling optical illusion in an upcoming edition of Current Biology. The illusion is very simple and I was quite surprised that it actually works. A cloud of colored dots is arranged in a circle around a central fixation point. In one condition, the dots gradually change color, but they don't move. As you would expect, it is very easy to spot the color changes in this condition. However, in another condition, the dots move around as well as change color. Surprisingly, in this condition the color changes are extremely difficult to detect! This is demonstrated quite nicely in the video below (provided by the authors).

How does the illusion work? An important clue is that retinal motion is required. If you match the movement of the dots with your eyes, thus eliminating the retinal motion, it becomes considerably easier to detect the color changes (not as easy as when the dots are static, but this is presumably because it is difficult to match the movement perfectly). Simply put, this suggests that we detect the color changes with neurons that “see” only a small part of our retina. If the dots move around on our retina, they are continuously “seen” by different neurons, and this compromises our ability to detect changes.

References

How would you like to have a publication in a prestigious scientific journal at the age of 9? In a forthcoming paper in Biology letters, children from a British elementary school describe a study that they have (largely) designed and executed themselves.

The experiment was as follows. In a training phase, bees learned that they could get a sugar-reward by flying to a small square in the center of a larger square. Sometimes the small square was blue and the surrounding square was yellow and sometimes it was the other way around. To learn this task, the bees had to use both spatial (center square vs surrounding square) and color cues (since the squares were defined by color). In the test phase, they found that the bees had successfully learned to solve this “puzzle”.

As the children say, “the experiment is important because no one in history (including adults) has done this experiment before”. Of course, the reason that the paper has attracted so much attention is because of the kids. But still, I think it is laudable that, in a comment accompanying the paper, Biology Letters focuses mostly on the scientific content and is not patronizing at all.

The paper can be downloaded for free and, unlike many scientific papers, it is quite readable, so go ahead and take a look!

Photo: Bombus Terrestris (source: Wikimedia Commons)

References

A few months back I bought an e-reader. An IRex (DR800S) to be specific. This is my second e-reader, to be even more specific, because the Sony (PRS600) that I used before had an unfortunate accident. Although I occasionally use the e-reader to read books (not too often, though, I promised myself that I would not let it stand in the way of having pretentiously well-stocked bookshelves), my main use for it is to read academic papers. I thought my experiences might be of some use to anyone who is thinking of buying an e-reader for the same purpose.

Initially, I wanted to buy an e-reader with a small display, which are considerably cheaper than the large ones, and just scroll through the pdfs like you would on a regular computer. Luckily I didn't, because e-readers are way to sluggish to comfortably scroll through a document. This is because e-ink displays have a very low refresh rate (i.e., it takes quite some time for the image to change). Most e-readers have the option to reformat (reflow) text, which means that the reader tries to increase the font size while maintaining a reasonable layout. For books, which tend to have a fairly straightforward layout, this works fine, but for multicolumn .pdfs (i.e., most academic papers) the results are disastrous. So basically, if you want to read academic papers, you will want an e-reader with a sizable display. The IRex has an 8 inch display, which is just large enough …

OpenSesame 0.17 is available! In addition to bug-fixes and numerous refinements to the graphical interface, there are a few noteworthy new features:

• There is now a debug window, which is invaluable when creating Python inline code. You can print to the debug window using the standard Python 'print' statement. The debug window also includes a simple Python interpreter.
• Added a timeout option to response items.
• Added an auto response mode, in which OpenSesame simulates responses. This can be very handy when you want to give your experiment a test run, but rather not spend an hour sitting behind your computer pressing keys.
• Added plugins! You can (relatively) easily extend OpenSesame's functionality through plug-ins. Four plug-ins are already included:
  • fixation_dot: a convenience plugin for displaying central fixation dots.
  • text_display: a convenience plugin for presenting text displays.
  • text_input: a response collection plugin which provides a text input field.
  • advanced_delay: a timing plugin which waits for a random interval with a specified mean and standard deviation.
• Another tutorial. This is not really a feature, of course, but it is nevertheless a very useful addition. You can download the tutorial here (PDF format).

Get it here!

Today I would like to highlight a study by Jan Theeuwes (my PhD supervisor) and myself, to celebrate that the paper is now officially available. (It's still in press, but Psychological Science provides “online first” access to articles. If you do not have access to Psychological Science, you can find an unofficial postprint here.)

In this paper we focus on the “problem” of eye movements. This may seem strange. Clearly, the ability to make eye movements is very adaptive, because it allows us to quickly scan the environment without having to make head (or body) movements, which are costly in terms of time as well as energy. So what's the problem?

The “problem” that I'm referring to is that with every eye movement, the retinal image of the world changes enormously. Therefore, if we were to take changes in the retinal image as evidence for changes in the world around us, we would perceive a dizzyingly unstable world. Which, clearly, we don't. We may be vaguely aware of the fact that we make eye movements, but subjectively it does not feel as though eye movements interfere with our sense of “visual stability”. Apparently, the visual system somehow compensates very effectively for eye movements.

Another phenomenon on which we focus in the paper is “inhibition of return” (IOR). IOR refers to the fact that after we have attended to some location, either covertly (i.e., from the corner of our eye) or by looking at that location, we ignore that location …