Cognition Laboratory Experiments

John H. Krantz, Hanover College,

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Mental Imagery



Statistical Concepts

Hanover College
Psychology Department

Instructions for the
Mental Rotation Experiment


When you click on the link below, you will be presented with the experiment setup screen.  On this screen will be the variables you can set to define your condition.  Here is a list of the variables and their settings.  Not all variables will be visible all the time.  Only those variables appropriate to the stimulus and other settings will be shown.  So changing some values may alter what is shown on the setup screen.

Variable Settings
Stimulus Type The rotation stimulus: Random 2D figure, Letter, String, Original 2D1 and Original 3D1.
Number of Rotation Angles Number of levels of rotation variable (includes 0 and 180 deg).
Should the left stimulus be allowed to rotate or be fixed If the left hand stimulus is allowed to rotate, then it can assume any angle and be either the original image or the mirror image.  If the left hand stimulus is fixed, it is not rotated nor will it be a mirror but always the normal image.
Stimulus Size If Random 2D figure, how big is the stimulus
Stimulus Contrast The brightness difference between the background and the foreground.  The foreground is always darker.  It is a percentage of the maximal change possible on the display.
Letter Stimulus to Display If a letter figure, what letter to display
String Stimulus If a string stimulus, what string to display
Trials per level The number of presentations of each rotation angle
Font Size If using a letter stimulus (from 12 to 64 point)
Distance from Fixation How far from the fixation stimulus is the center of the stimulus (in proportion of distance from center to edge)
Delay before stimulus How long between your response and the next trial
Stimulus on till response Is the stimulus on until you respond or only one for a given period of time.
Duration of Stimulus If stimulus is only on for a give period of time, how long is that interval.

After you have finished making your settings, press the Done button at the bottom of the screen.  The Mental Rotation experiment screen will then be presented. 

Press the space bar to begin the experiment.  A fixation mark will appear for the indicated time.  The stimulus will be presented after the delay time. As so as the stimuli are on, you may respond.  There are several ways to respond:

  • Press the buttons at the bottom of the screen:
    • Same if the two figures are identical
    • Mirror if the two figures are mirror images of each other
  • Press the s key for same and m key for mirror.
  • Press the z key for same or / key for mirror

It is good to have your figures ready over the buttons when the stimuli are presented.  After you have responded, the next trial will begin.

At the end of the experiment, your results will be presented.  The results will be the reaction time and accuracy for each angle.  The same image data and mirror image data will be presented separately.  In accuracy, a 1.0 is a perfect performance.  You can also get your trial by trial results.  Closing your results window(s) will take you back to the setup window so you can run another experiment.

Click here to start the experiment.



  • The idea to fix the left hand stimulus comes from Dwayne Guenther, Dana Newton, and Alexis Rose of Hanover College
  • The idea to manipulate the contrast of the image comes from Amber Adkins, Becky Nixon and Cole Wyatt of Hanover College



Cooper, L. A. (1975).  Mental rotation of random two-dimensional shapes.  Cognitive Psychology, 7, 20-43.

Metzler, J. & Shepherd, R. N. (1974).  Transformational studies of the internal representation of three-dimensional objects.  In R. L. Solso, ed., Theories of cognitive Psychology: The Loyola Symposium. Potomac, MD. Lawrence Earlbaum Associates.



1  The two dimensional shape referred to as Original 2D is take from form H by Cooper (1975) also used elsewhere.  The orginal 3D shap is taken from Metzler & Shepherd (1974).