Mental Rotation of 3D Objects

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

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

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.

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 ??

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

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%

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.

Effect Of Training on Mental Rotation

Results after the first trial (male subject)

15 pairs

Effect Of Training on Mental Rotation

Results after the second trial with the same male subject

15 pairs

Effect Of Training on Mental Rotation

Mental rotation can be strengthened by training

Training helps to process information as quickly and accurately

10 pairs

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)

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.

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.