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Experiment Description: Mental Rotation

The study of mental rotation began with the classic work of Shepard & Metzler (1971) and is described in detail in the first part of Chapter 7 in Matlin (2005). Demonstration 7.2 involves the actual three-dimensional stimuli that were used in Shepard and Metzler's (1971) original mental rotation task. In their study, participants were shown two shapes and asked to decide whether they were the same shape or mirror images. As the figure in Demonstration 6.1 indicates, the second shape was created by rotating the original object (or a mirror image of the object) around a central axis (depth or picture plane). Participants reported that to complete the task, they mentally rotated one of the shapes to bring it into alignment with the other. Consistent with their participants' reports, Shepard and Metzler (1971) found that the greater the angle of rotation between the two objects, the longer the decision (see Figure 7.1, p. 213). In other words, just as it takes longer to physically rotate an object a greater distance, the mental rotation of an imagined object follows that same principle.

In this experiment, a normal letter or a reversed letter will be presented in different angles of orientation and you will be required to indicate whether the letter is normal or reversed as quickly as possible. There will be eight different conditions that represent different angles of rotation. You will test whether your reaction time to make your decision (i.e. the dependent variable) is systematically related to the angle of rotation (i.e. the independent variable). You will examine this relation between rotation angle and response time for both positive responses (i.e. the letter is normal) and negative responses (i.e. the letter is reverse).

Participant Instructions: Mental Rotation

On each trial in this experiment, a plus sign will appear briefly in the center of the screen for 500 milliseconds followed by large upper-case 'F'. The letter F will be presented at one of eight orientations, and will either be a normal 'F' or a reverse/mirror-image of an 'F'. Your task is to determine whether the symbol is a normal or a reversed 'F', and to respond as quickly as possible by pushing the "Z" key if the symbol is reversed, or the "/" key if the symbol is normal. The computer key assignments will be displayed at the top of the screen but you may also want to tape the terms 'normal' and 'reversed' to the appropriate computer keys to help you keep track of the computer key assignments.

If the response is correct, the next trial will begin in 1500 milliseconds. If the response is not made within 5 seconds, or if the response was incorrect, or if an invalid key was pressed, a brief tone will be presented and the next trial will begin in 1500 milliseconds. The stimulus is equally likely to be normal or reversed at each of the eight orientations.

There are 3 trials at each of the 8 orientations for each symbol (reversed or normal) for a total of 48 trials per block. There are 5 blocks of 48 trials but the first block is a practice block and will not be used in the calculation of the summary data. Nevertheless, the practice trials are important for you to focus on the task and practice making your decision as quickly and as accurately as possible. You will have an opportunity to take a short break between lists.

The raw data from the experiment (192 responses) will be placed in a file called DROT.DAT on your computer and can be examined by using the View Raw Data button.

To summarize this data, click on the Analyze Raw Data button to compute the mean and standard deviation of the reaction times for correct responses in each of the eight orientations for each type of response (reverse image vs. normal image). This button will also calculate the number of valid trials for each condition or the number of trials where a correct response was provided.

The summarized data will be placed in a file called AROT.ANL on your computer. To view the results, click on the View Summarized Data button. This summary data is important and will be necessary to prepare an APA style figure to include with your paper. AROT.ANL is a simple text file and can be read and printed with any word processor. Please note that although the summary data appear in tabular form, the format is not in APA style.

There should be 16 sets of data that will look like the following.

Orientation = 0 Response Type = 1

The first line specifies the condition by describing the Orientation and Response Type using the legend below. The second line provides the actual reaction time in milliseconds, standard deviation, and the number of valid trials. In the example above, the average response time for the condition where the target was a normal F in the vertical orientation was 1087.33 ms with a standard deviation of 182.33 based on 12 trials. As indicated earlier, there are eight different orientations and two response types that produce 16 separate conditions.

0 = 0°or vertical
1 = 45° clockwise from vertical
2 = 90° clockwise from vertical
3 = 135° clockwise from vertical
4 = 180° clockwise from vertical
5 = 225° clockwise from vertical
6 = 270° clockwise from vertical
7 = 315° clockwise from vertical
1 = Normal F
2 = Reversed F

In your graph, plot the orientation variable on the abscissa (X axis) with reaction time on the ordinate (Y axis). The abscissa should have 8 marks, one for each angle of orientation. Use separate lines for the normal and reversed figure responses.

To view the results of previous participants, click on the Display Group Data button. This button will display the average reaction time for the three conditions. You can use this information to compare with your own performance.

Run Experiment

If you have successfully installed Java Web Start but you are still being taken to the Java installation page, please click on this direct link to the experiment installer.

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Last Modified: Monday, 27-Jun-2005 23:33:34 MDT