Sensation & Perception: "Ch. 5 Perceiving Objects and Scenes"

Why Is It So Difficult to Design a Perceiving Machine?

• The stimulus on the receptors is ambiguous. (inverse projection problem)

• Objects can be hidden or blurred

• Objects look different from different viewpoints (viewpoint invariance)

What is the Inverse projection problem?

An image on the retina can be caused by an infinite number of objects.

What is viewpoint invariance?

the ability to recognize an object regardless of the viewpoint

What is perceptual organization?

• Process by which elements in the environment become grouped to create our perception of objects.

What are the two components of perceptual organization?

• Grouping

• Segregation

What is Gestalt Psychology?

The whole differs from the sum of its parts

According to gestalt psychology, perception…

is a result of perceptual organization

What is structuralism?

perception is the sum of lots of small sensations

However structuralism explain can’t explain all perceptions such as..

apparent movement and illusory contours

What is apparent movement?

a. one light flashes

b. darkness

c. the second light flashes

d. flash-dark-flash

What are illusory contours?

Edges or contours are perceived but are not actually there

Name the principles of perceptual organization: (7)

• Good continuation

• Pragnanz

• Similarity

• Proximity

• common fate

• common region

• uniform connectedness

What is Good continuation?

connected points resulting in straight or smooth curves belong together

What is Pragnanz?

every stimulus is seen as simply as possible

What is Similarity?

similar things are grouped together

What is Proximity?

things that are near to each other are grouped together

What is common fate?

things moving in same direction are grouped together

What is common region?

elements in the same region tend to be grouped together

What is uniform connectedness?

connected region of visual properties are perceived as a single unit

What are figure-ground segregation properties? (4)

 The figure is more “thinglike” and memorable than the ground.

 The figure is in front of the ground.

 The ground is more uniform and extends behind figure.

 The contour separating figure from ground belongs to the figure (border ownership).

What figural cues determine which area is figure?

• elements located in the lower part of the displays

• convex side of borders

Gestalt psychologists believed that ______ and ______ played a minor role in perceptual organization.

experience, meaning

Gibson Experiment showed that ________.

figure-ground can be affected by meaningfulness of a stimuli.

What are geons?

individual geometric components that make up objects

A scene is a view of a real world environment that contains (2)

• background elements.

• objects organized in meaningful ways with each other and the background.

What is the differences between objects and scenes?

– A scene is acted within

– An object is acted upon

What are the global features of scenes? (5)

– Degree of naturalness

– Degree of openness

– Degree of roughness

– Degree of expansion

– Color

What are regularly occurring physical properties of the environment?

Physical regularities

What is the oblique effect?

people perceive horizontals and vertical more easily than other orientations

According to regularities in the environment: uniform connectedness

objects are defined by areas of the same color or texture

What is the Light-from-above heuristic?

light in natural environment comes from above us

What are semantic regularities?

characteristics associated with the functions carried out in different types of scenes.

Semantic regularities are related to the ______ of the scene?

meaning

What is the theory of unconscious inference?

Some perceptions are the result of unconscious assumptions we make about the environment

What is the Likelihood principle (Bayesian inference)?

objects are perceived based on what is most likely to have caused the pattern

What is Predictive Coding?

the brain actively predicts incoming sensory information based on past experiences.

______contains neurons responsible for recognizing faces

Fusiform face area (FFA)

________responds best to indoor and outdoor scenes (spatial layout)

Parahippocampal place area (PPA)

_______responds best to pictures of full bodies and body parts.

Extrastriate body area (EBA)

What is the inability to recognize faces?

Prosopagnosia

What is Binocular Rivalry?

when each eye receives a different image, the brain can only perceive one image at a time

Object activate the ______.

Parahippocampal place area (PPA)

Faces activate the ______.

Fusiform face area (FFA)

Names the areas of the brain involves in face perception?

• Occipital cortex:

• Fusiform face area (FFA):

• Amygdala: emotional aspects of faces

• Superior temporal sulcus (STS) - responds to where the person is looking and to mouth movements

• Frontal Cortex

The Occipital cortex is responsible for..

initial processing of face information

The Amygdala is related to..

emotional aspects of faces

The Superior temporal sulcus (STS) responds

to where the person is looking and to mouth movements

The Frontal Cortex is activated

when evaluating facial attractiveness

________ is the most important stimuli in an infant’s environment?

Human faces

Newborns prefer their _______to a stranger’s

mother’s face

How is Gestalt psychology different from structuralism?

In structuralism: the whole = to the sum of its parts (sensations combine or “add up” to create complex perceptions)

In gestalt: the whole differs from the sum of its parts

How does apparent movement reject structuralism?

Apparent movement can’t be explained by sensations alone, because there is nothing in the dark space between the flashing lights.

How does illusory contours reject structuralism?

Sensations can’t explain illusory contours, because there aren’t any sensations along the contours.

How does the principles of organization differ from figural cues?

Figural cues: separate the ground and figure

Principles of organization: groups together elements of an image

How does our brain determine what is figure and what is ground?

figural cues determine how an image is

segregated into figure and ground.

What are convex borders?

(borders that bulge outward)

A general description of the type of scene is called..

the gist of a scene

What enables observers to perceive the gist of a scene so rapidly?

global image features

The Palmer Kitchen experiment demonstrated

that a scene schema can influence perception

Describe the Palmer Kitchen Experiment

Palmer first presented a kitchen scene to participants and then briefly flashed one of the target pictures on the right.

Observers to identify the object in the target picture, they correctly identified an object like the loaf of bread (which is appropriate to the kitchen scene) 80% of the time, but correctly identified the mailbox or the drum (two objects that don’t fit into the scene) only 40% of the time.

Ultimately, Palmer’s observers used their knowledge of kitchens to perceive the briefly flashed loaf of bread.

Which part of the temporal cortex is active when you look at a scene?

Parahippocampal place area (PPA)

Which part of the temporal cortex is active when you look at a hand?

Extrastriate body area (EBA)

How does binocular rivalry work?

In everyday perception, our two eyes receive slightly different images because they are in slightly different locations. These two images, however, are similar enough that the brain can combine them into a single perception.

But if the two eyes receive totally different images, the brain can’t combine the two images.

__________occurs, in which the observer perceives either the left-eye image or the right-eye image, but not both at the same time.

binocular rivalry