Introduction

Definition

Mental rotation is a process of imagination. It is imagining what an object or a drawing would look like if it would be rotated.

Mental rotation tasks are difficult. In these tasks, you typically see at least three stimuli like in the example figure. The top one is the one that matches only one shown at the bottom. But the matching stimulus is rotated. Mental rotation time is the time it takes you to find which one matches. It is a well established fact that men and women perform differently on this task.

In this lesson, we are going to rotate 2-dimensional (2D) stimuli. 2D stimuli are those without depth (like in the figure below). Rotating stimuli with depth (3D) is more difficult than rotating 2D stimuli.

In the above screen shot, you see three two-dimensional stimuli. For this lesson, we use 2D stimuli because they are much easier to create.

The grey stimulus at the top is the one you need to match with one of the red ones. In order to match the grey stimulus, you need to imagine what it looks like when it is rotated. In this example, the right one matches, and thus needs to be clicked (as indicated by the little grey mouse cursor).

 If you wish to make 3D stimuli and rotate them in different ways, you should have a look a 3D drawing program, such as the Art Of Illusion, which is free and easy to use to all computer platforms. Click here to go to its webpage.

Do it yourself

In the following demonstration, you will need to find out which two object match each other. You can only do that if you mentally rotate the objects and see which ones match. In this example, the stimuli are 2 dimensional, or 2D. In psychology, the most common mental rotation experiments have stimuli with depth, that is 3D.

Data analysis

At the end of the study, you can save your data. It is very easy to analyze using a simple spreadsheet program. The first column is the block you did, and you might want to discard the "training" trials (the first 5 rows).

The reaction time is in the 4th column. When the 5th column has value one, the participant responded correctly, and when it has value 2 the participant responded incorrectly.

Ideas for home work

• Women and men perform differently on the mental rotation paradigm. What does this mean? What does the difference look like? How can it be explained?

• Create your own or find 3D mental rotation stimuli and run the experiment with them. Compare performance in the 2D and 3D conditions? What do you notice? What are the basic differences between the 2D stimuli in the lesson demonstration and other studies? Do you think the differences matter?

• The following is in regard to the demonstration code: Are ten trials enough to determine well whether people work at chance level? What is the minimum number of correct trials in this task to show that people perform better than chance level? Given your answer, do you think ten trials is enough? How could you improve the paradigm?

Reading material

• Shephard, R. N. and Metzler, J. (1971). Mental Rotation of Three-Dimensional Objects. Science, 171, 701-703.

• Collins, D.W. and Kimura, D. (1997). A Large Sex Difference on a Two-Dimensional Mental Rotation Task. Behavioral Neuroscience, 111, 845-849.