The document describes several experiments on mental rotation of 3D objects. It found that response times increased linearly with the degree of rotation of objects, suggesting people mentally rotate objects to compare them. Males performed better than females on accuracy and response time. Training can improve mental rotation skills over time by decreasing response times. The number of axes and direction of rotation also impact response times. Future work could explore these effects in more populations and with refined experiments.

1. Mental Rotation of 3D Objects

2. Mental Rotation Task
Visual stimulus  Mental rotation of stimulus  Response
 Two images presented simultaneously
 Images of identical or “mirror reflected” objects
 Subjects indicated whether two images depicted
same object
 Responded by pressing 1 (similar) or 2 (not similar)
 Record response times and plot graphs

3. Mental Rotation Task Results
Response times increased linearly with orientation (for both depth, picture-
plane rotations and mixed rotations)
Suggests that subjects are “mentally rotating” images to determine match.
Response Time Vs Degree of Rotation Graph

4. Object recognition
Two fundamental approaches to human object recognition
I. Alignment approaches
Object recognition through alignment process
II. Structural description approach
Decomposition of features included in an object
Describe the objects’ shape in terms of their parts and relation
among the parts.

5. Mental Rotation
 Data are linear !
 Data Every additional 50° of stimulus rotation increased RT by 1000 ms
 Interpretation Objects are mentally rotated at a rate of 50° per 1 s
 Some have exceptionally good mental rotation skills.
 Some can learn and train very fast.
 Effect of Training ??

6. Hypothesis
Mental rotation can be separated into the following cognitive
stages:
1. Create a mental image of an object
2. Rotate the object mentally until a comparison can be
made
3. Make the comparison
4. Decide if the objects are the same or not
5. Report the decision

7. Effect Of Gender on Mental Rotation
Male Female
Males outperformed females both in terms of response times and number of
correct responses.
Average Accuracy(Females) 76%

8. Effect Of Gender on Mental Rotation
 In adult populations, it is generally accepted there is an overall male advantage on
spatial tasks and an overall female advantage on verbal tasks.
 Different neuropsychological functions such as shape perception, spatial reasoning
and problem solving are better in men than in women.
 Mental rotation is a complex cognitive skill involving shape perception and spatial
reasoning.

9. Effect Of Training on Mental Rotation
15 pairs
Results after the first trial (male subject)

10. Effect Of Training on Mental Rotation
15 pairs
Results after the second trial with the same male subject

11. Effect Of Training on Mental Rotation
10 pairs
 Mental rotation can be strengthened by training
 Training helps to process information as quickly and accurately

12. Effect of Axis and Direction on Mental
Rotation
 Subjects took more time to respond if the objects had both in-plane
and depth plane rotations
 Explanation they gave was they had to rotate around two axis to arrive
at the results
 Some didn’t rotated and just counted the number of blocks and the
orientation of the boxes if the pairs were rotated in both 2D and 3D or
some even just guessed randomly
 Response Time = Time to analyze the pairs + Time to rotate + additional
time for changing the axis or changing the direction or changing the
reference pair (if needed)

13. Effect of Incoming Samples Pattern on
Mental Rotation
 Subjects try to guess the output of next incoming sample from
previous experience.
 Response Time and Probability Distribution of Incoming Samples.
 Response Time less if one class of samples is coming continuously.

14. Future Work
1) Increase the number of subjects, number of trials and number of stimuli to
further establish the results.
2) Improve precision in measurements by refining the experiment design. This
will enable to find the improvement in the above results.
3) Effect of age on mental rotation because in other fields age has been
shown to change the way people perceive images and objects in their
environment.
4) How males and females mentally rotate objects could be looked into with
more detail.
5) People from different backgrounds etc.
6) Mental Rotation and intelligence.