Mental Rotation

Mental rotation experiment

Files needed:

  • MentalRotation.psyexp
  • MentalRotation.xlsx
  • normalr.jpg
  • reversedr.jpg
  • error.wav

Overview.  The MentalRotation.psyexp program runs a variation of Cooper & Shepards mental rotation experiment, examining the time need to make judgments about rotated objects.  On each trial an uppercase R or a mirror image of an R is presented at one of several possible orientations..  Subjects indicate via keypress whether the letter is a normal R or a mirror-reversed one.

Details.  Run the program by double-clicking on the MentalRotation.psyexp file.  This will launch PsychoPy with the experiment timeline loaded.  Run the experiment by selecting “run” from the PsychoPy menu (the green running person).  A dialog box will appear in which the student can optionally enter their name or initials.  Any string entered will become the first part of the name of the data file.

On each trial an R or mirror-reversed R is presented at the center of the display at one of 8 orientations.  Subjects are to indicate which stimulus is present: z=normal, /=mirror-reversed.  After a practice block of 16 trials, subjects serve in 4 test blocks of 48 trials each.  Each block contains 3 replications of each of the 16 combinations of 8 orientations * 2 levels of mirror-reversal.

Other details of the method can be learned by examining the timeline and the events in PsychoPy.  In cases where attributes of the events are variable, the variables are typically specified in the provided Excel files.

Programming notes.  Orientation is specified in the excel file—8 different orientations are used.  Condition is also specified, but here rotations that are clockwise from vertical are given the same condition name as counterclockwise rotations of the same magnitude.  Thus, if the “condition” variable is used, the results will be coded for the amount of rotation from vertical, irrespective of the direction of rotation.  If you use the “orientation” variable then counterclockwise and clockwise rotations will be treated separately.

Data analysis.  The data are in a *.CSV file in the “data” folder in the Psych/Lab folder.  Double-click on this file to open it in Excel.  Each row corresponds to a trial.  Entries in the column labeled condition show the condition for that trial. Keyresponse.RT contains the reaction time (in seconds).  Keyresponse.corr codes whether the response was correct (1) or incorrect (0).  The first one (or more) sets of trials might be practice and should not be analyzed.  See the instructions elsewhere for creating a pivot table to summarize the data.