Topic 4: Perceiving Objects and Scenes

Question 1

The importance of knowledge for perception is highlighted by what difference?

Answer 1

The difference between human perception and computers/AI

Question 2

What are five situations/domains in which computers often struggle with object recognition?

Answer 2

When different objects are similar sizes/shapes

Degraded conditions

Unexpected situation

Hidden objects

Viewpoint invariance

Question 3

What are four difficulties in perception for humans?

Answer 3

The image on the retina is ambiguous, such that multiple objects can create a similar or the exact same image on the retina.

The image on the retina also does not always accurately reflect what is really “out there”

Often make “assumptions” or “predictions” about what is the most likely cause of what we are perceiving.

Viewpoint also plays a role and can impact the image on the retina as well.

Question 4

Object properties don’t change when the object turns

Answer 4

Viewpoint invariance

Question 5

Process by which elements are grouped & segregated to create a perception.

Answer 5

Perceptual organization

Question 6

The perspective that much like how individual atoms come together to form complete chemical structures, simple stimuli combine to form complete perceptions

Answer 6

Structuralism

Question 7

Approach that rejected the idea that perceptions were formed by “adding up” individual stimuli

Answer 7

Gestalt approach

Question 8

An illusion where movement is perceived when nothing is moving

Answer 8

Apparent motion

Question 9

What are the seven Gestalt principles of perceptual organization?

Answer 9

Principle of good continuation

Principle of pragnanz/good figure/simplicity

Principle of similarity

Principle of proximity

Principle of common fate

Principle of common region

Principle of uniform connectedness

Question 10

Points that, when connected result in straight or smoothly curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path

Answer 10

Principle of good continuation

Question 11

Every stimulus pattern is seen in such a way that the resulting structure is as simple as possible

Answer 11

Principle of pragnanz/good figure/simplicity

Question 12

Similar things appear to be grouped together.

Answer 12

Principle of similarity

Question 13

Things that are near each other appear to be grouped together.

Answer 13

Principle of proximity

Question 14

Things that move in the same direction appear to be grouped together

Answer 14

Principle of common fate

Question 15

Things that are within the same region of space appear to be grouped together; Can override proximity

Answer 15

Principle of common region

Question 16

Connected objects/regions with similar visual properties are perceived as grouped together

Answer 16

Principle of uniform connectedness

Question 17

The perceptual separation of an object from its background

Answer 17

Figure-ground segregation

Question 18

A figure-ground pattern that perceptually reverses as it is viewed, such that the “figure” and the “ground” are often ambiguous

Answer 18

Reversible figure-ground

Question 19

What are the four “rules” for deciding what is the figure and what is the ground?

Answer 19

The figure is seen as being in front of the ground, and the ground is seen as extending behind the figure

The shared border is perceived to belong to the figure, and not the ground (see the previous image)

Things that are lower in our field of view are more likely to be perceived as the figure.

Things that align with expectations/previous knowledge are more likely to be the figure.

Question 20

Proposes that objects are comprised of individual geometric components called geons, and we recognize objects based on their arrangement

Answer 20

Recognition by Components (RBC) theory

Question 21

Three-dimensional shapes that are the building blocks of objects and can be arranged in different ways to form different objects (RBC)

Answer 21

Geons

Question 22

Name one advantage and two disadvantages to the RBC approach

Answer 22

Advantage: Is unaffected by viewpoint invariance
Disadvantages: Some objects simply can’t be represented easily (abtract objects), can’t easily distinguish within the same category

Question 23

An environment that contains background elements alongside multiple objects that exist relative to each other

Answer 23

Scene

Question 24

Regularly occurring physical properties of the environment

Answer 24

Physical regularities

Question 25

Name two key physical regularities

Answer 25

Horizontals and verticals

Light-from-above assumption

Question 26

Characteristics associated with functions carried out in different types of scenes

Answer 26

Semantic regularities

Question 27

We look for (and often find) what we expect to find in a scene based on knowledge

Answer 27

Scene schema

Question 28

What do scene schemas do in relation to perception?

Answer 28

Assigning a meaning to a scene can help us determine what an object probably is within that scene, even when we can’t necessarily perceive the scene very well