Individuals must rely on visual mental imagery—the ability to conjure images in one’s mind’s eye—to accurately perceive the world and guide actions.
For example, mental imagery is used to visualize a route when planning directions to particular location, or what a house might look like if it were remodeled.
Experimental psychologists can measure a person’s visual mental imagery through the use of a mental rotation paradigm, which involves identifying rotated versions of familiar characters and distinguishing them from rotated versions of their mirror images.
Using the mental rotation procedure, this video will demonstrate how to design stimuli and conduct an experiment, as well as how to analyze and interpret results investigating visual mental imagery.
In this experiment, participants are presented with stimuli and asked to distinguish whether subsequent stimuli are rotations of the original item or of its mirror image.
In this case, the task stimuli consist of letters, such as R and g, as well as numbers, like 4 and 7, all printed in Helvetica Light font.
Two versions of the letters and numbers are produced: the original and a flipped, mirror image. The characters are then manipulated, such that each one is rotated by an increasing increment of 15°, starting at 0° and ending at 180°.
During each trial, participants are presented with one of the four manipulated characters and then asked to decide from two possible choices which one is the rotated version of the original item as quickly and accurately as possible.
Thus, the dependent variable is response time—how long it takes for the participant to make a response.
It is hypothesized that response times will be faster for characters that have little rotation, compared to those that are rotated the most. In other words, the response times are longer the more a character is rotated from its canonical orientation.
To begin the experiment, gather stimuli sheets that have been created for each individual trial. For each trial, note that one of the four non-mirror images is printed at the top, and the two choices are located on the bottom of the page.
Number the back of each page from 1–52, which is called the ‘number tag.’ To randomize the order, shuffle the test pages.
To more easily associate the results with the content of each trial, create a response sheet that includes the trial number, number tag in the order of presentation, response given, and response time.
As the last preparation step, gather a stopwatch and an assistant.
When the participant arrives, explain the instructions to them using a demo page. Note that one of the characters, its mirror image, and a couple of examples of the character at one of the rotations is shown.
Next, place the test pages facedown between the experimenter and the participant.
During each trial, once the assistant starts the timer and says, “Go,” flip over a page for the participant.
When the participant reports a response, stop the timer. Then, record the response time and the answer on the response sheet. Repeat this procedure for all 52 trials.
Once the experiment is complete, create a digital copy of the response sheet, including the number tags in numerical order, responses given, response times, and correct answers.
Mark whether the responses given were correct by entering a 1 in the ‘Answer Correct?’ column or a 0 if incorrect.
For the correct trials, plot the average response times for each character shown as a function of rotation. Note that the response times increase proportionally with the degree of rotation. These results suggest that the brain simulates the physical transformations.
Now that you are familiar with designing a mental rotation experiment, you can apply this approach to answer specific questions about visual mental imagery.
Practically speaking, people who are especially good at visual thinking about physical spaces can be identified through the mental rotation task. Certain individuals are exceptionally good at using mental imagery to guide their actions—like architects and mechanical engineers.
In addition, researchers use functional magnetic resonance imaging to investigate brain regions involved in mental rotation.
When people mentally rotate objects without looking at them, there is an enormous amount of brain activity in the visual cortex in particular, and in regions such as the parietal lobe—brain areas generally thought to be involved in seeing. In other words, the brain systems used to actually see visual stimuli are also used to imagine visual stimuli.
Finally, researchers examine mental rotation in virtual reality to study how mental imagery is involved in navigating through different spatial environments and obstacles.
You’ve just watched JoVE’s introduction to conducting a mental rotation experiment. Now you should have a good understanding of how to design and conduct the experiment, and finally how to analyze and interpret the results.
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