In the video below, you see an animation of the classic video-game Pac-man ¹. But there is something weird about Pac-man. Can you spot what it is? (For the best effect, play the video in full-screen!)

In fact, as you probably noticed after a while, Pac-man is not doing anything weird at all. It’s the maze that is continuously changing. And not just a wall being added or removed here and there! The whole maze, with the exception of the tiles around Pac-man, is completely randomized with every new frame.

How can it be so easy to miss these large changes that are happening right in front of your eyes?

This video is a somewhat unusual demonstration of a classic phenomenon called change blindness, which was first described by Ronald Rensink, Kevin O’Regan, and James Clark. A typical change blindness experiment is similar to a “spot the differences” game, in which two slightly different images are presented side by side, and you have to, well, spot the differences. This can be very difficult!

Source: Wikimedia Commons

But spotting differences becomes very easy when the same two images are presented one after another at the same location. Now differences correspond to unique changes in the image. These unique changes grab your attention, and therefore really “pop out”.

Source: Wikimedia Commons

However, by adding a blank in between the alternating images, the differences again become difficult to detect. The reason is that, because of the blank, the whole image changes …

Over the past month I ran a small poll on the OpenSesame website about the attitude of researchers towards open access (OA) in academic publishing.

I received 767 responses, where each question was answered only once per IP address. Questions appeared in random order, and the order of the answers was randomized as well. The usual caveat applies, though: Because I ran the poll on the OpenSesame page, most respondents are presumably early-career experimental psychologists, and not representative of the ‘average’ scientist. Nevertheless, I think it’s interesting to see how this particular segment of the research population feels about OA.

So here we go.

Let’s first take a look at the general attitude towards OA. Clearly, as you can see in the figure below, respondents overwhelmingly perceive OA as a good thing. A minority indicates that they are not too interested in the matter, and no-one expresses an outright dislike of OA.

Principles are one thing, but of course what really matters is what people will do in practice. Most respondents indicate that they are likely to submit to an OA journal. However, relatively few indicate that they have actually done so in the past, despite the fact that some well known OA journals (notably PLoS ONE) have been around for years. But then again, many respondents are probably early career academics with few publications on their name.

I think it’s also interesting to consider the reasons that people might have for (not) submitting to an OA …

PsychoPy is a powerful Python library for creating the type of stimuli that are frequently used in psychological and neuroscientific experiments. I use it all the time, mostly from within OpenSesame, but I remember that I initially found working with PsychoPy quite daunting. This is because PsychoPy takes a very different approach to stimulus generation than most people are used to. You have to think in terms of patches, textures, and, masks, rather than in conventional drawing primitives, such as rectangles and lines (although newer versions of PsychoPy also support these drawing primitives). Therefore, I decided to write a short tutorial that explains the basics of working with PsychoPy.

In this tutorial, I will explain how to use textures and masks from the ground up. I will assume very little prior knowledge, except a basic understanding of Python. I will assume that you are running OpenSesame, which you can download from here, and comes bundled with all necessary Python libraries. The code snippets below can be pasted directly into an OpenSesame inline_script item. You will probably want to insert a keyboard_response after the inline_script item that contains the code, so you that have the chance to see your stimuli before the experiment finishes!

For your convenience, you can download an OpenSesame template for this tutorial from here:

• Download OpenSesame template (Follow the link, click on download, and save as .opensesame file)

Overview

• Example 1: The basics
• Example 2: A simple texture
• A note on colors
• Example 3: A colorful texture …

In the animation below, you can see a Christmas tree full of baubles. The baubles are arranged in two more-or-less vertical columns, but not quite: Some are shifted a bit to the left, some a bit to the right. Or are they? In actuality, of course, the baubles are arranged in two perfectly straight columns. The apparent displacement is caused by the motion of the stripes on the baubles.

This illusion is a demonstration of motion-induced displacement: the phenomenon that the perceived position of an object is affected by its motion (or motion in the object’s environment, as I’ve shown before). This effect is particularly strong if an object’s position is ill-defined, for example because it has fuzzy edges like our baubles here.

The first to show this (that I know of) were Leonard Matin and his colleagues. They showed that two line-segments that rotated around a central dot appeared to be shifted in the direction of their movement. This is similar to what happens to the perceived position of the ‘baubles’ in the animation shown above: When the texture of the bauble is moving to the right, the position of the bauble appears to shift to the right as well. The fact that the bauble itself is not moving (just its texture) is a nuance that is lost on our visual system: Essentially any kind of nearby motion will ‘grab’ the object and perceptually drag it along.

The obvious question is whether motion-induced displacement serves a …

Since this post, the OpenSesame runtime has been ported to Android. This provides an even easier way to run experiments on a tablet device. For more information, see http://osdoc.cogsci.nl/getting-started/android/.

As you can see in the video below, it is possible to run OpenSesame on a tablet! This way you can take your experiments anywhere.

I will post more detailed instructions on the OpenSesame documentation page soon, but for now some basic info should get you started: The operating system that you see in the video is Ubuntu Linux. The tablet is a Nexus 7. Installing Ubuntu onto a Nexus 7 tablet is a straightforward process, and so is restoring the device to it's factory settings. Once you have Ubuntu running on your tablet, you can install OpenSesame directly from the Cogsci.nl PPA.