Chapter 3- Visual Perception

Question 1

Akinetopsia:

Answer 1

• Inability to perceive motion even though other aspects of vision seem normal
Can see difference in position (object that was here is now over there), but doesn’t see the object moving

Question 2

Retina

Answer 2

○ Light sensitive tissue lining back of eyeball

Fovea (center of retina)

Question 3

Cornea and lens

Answer 3

○ Focus incoming light
○ Muscle around lens tightens to bulge lens to focus nearby objects
Muscle around lens relaxes to flatten lens to focus far away objects

Question 4

Rods

Answer 4

Sensitive to low levels of light

Can distinguish different intensities of light

Can’t distinguish colour
More rods than cons farther away from fovea

Question 5

Cones

Answer 5

Less sensitive than rods

Need more incoming light to operate

Sensitive to colour differences

3 different types, each respond to different wavelengths

Important for acuity
§ Ability to see detail

In fovea, cons far out number rods (no rods at all in center of fovea)

Question 6

Bipolar cells

Answer 6

Intermediate cells that are stimulated by photoreceptors which then excite ganglion cells

Question 7

Ganglion cells

Answer 7

Spread uniformly across retina, but axons converge to form optic nerve

Question 8

Lateral Geniculate Nucleus (LGN)

Answer 8

Info from optic nerve sent here first, then transmitted to occipital lobe
Located in thalamus

Question 9

Lateral Inhibition

Answer 9

Once stimulated, cells inhibit activity of neighbouring cells

Question 10

Edge Enhancement

Answer 10

Lateral inhibition highlights a surfaces edge because cells in the middle will be inhibited more than cells at the edge

Question 11

Single Cell Recording:

Answer 11

• Animal is immobilized and has electrodes placed outside optic nerve or brain
• Various patterns on a computer flashed in front of animals eyes
Used to define a cell’s receptive field (size and shape of area in visual that the cell responds to)

Question 12

Centre Surround Cells

Answer 12

○ Center has one response, surrounding ring has opposite response
If both center and surrounding are stimulated, they cancel each other out

Question 13

Edge detectors

Answer 13

Fire at maximum only when a stimulus has an edge in a specific orientation (i.e. horizontal, vertical)

Will still fire when they detect a stimulus orientated in a different way, but not as strongly

Question 14

Area V1

Answer 14

○ Site on occipital lobe where axons from LGN first reach cortex
Contains cells to detect every kind of stimulus (horizontal, vertical…etc)

Question 15

Area MT

Answer 15

Neurons are acutely sensitive to direction and speed of movement

Question 16

Optic Nerve

Answer 16

Composed of P and M cells

Question 17

P Cells

Answer 17

§ Provide main input for LGN’s parvocellular cells

Specialized for spatial analysis and detailed analysis of form

Question 18

M Cells

Answer 18

§ Provide input for LGN’s magnocellular cells

Specialized for detection of motion and perception of depth

Question 19

Ventral Stream:

Answer 19

What System

Occipital lobe-> temporal lobe

Crucial for identification of visual objects

Damage can cause visual agnosia
Inability to recognize objects in visual field

Question 20

Dorsal Stream

Answer 20

Where System

Occipital lobe-> parietal lobe

Crucial for locating object in space

Damage can result in difficulty reaching out for objects

Question 21

Binding Problem:

Answer 21

Task of reuniting various elements of a scene that are initially addressed by different systems in different parts of the brain

Question 22

Spatial Position:

Answer 22

Various brain areas all keep track of where an object is

i.e. where a circle is, where the blueness is, where motion was detected, where things were still

Question 23

Neural Synchrony:

Answer 23

If neurons detecting 2 different attributes are firing together, then they must be detecting the same object
i.e. vertical line moving down stimulates neurons detecting orientation, and neurons detecting movement, therefore the are detecting the same object

Question 24

Neural Synchrony:

Answer 24

If neurons detecting 2 different attributes are firing together, then they must be detecting the same object
i.e. vertical line moving down stimulates neurons detecting orientation, and neurons detecting movement, therefore the are detecting the same object

Question 25

Attention:

Answer 25

• Attention important aspect in binding different features of a stimulus together
Synchronized neural firing observed when paying attention to a stimulus, not observed in neurons activated by an unattended stimulus

Question 26

Conjunction Errors

Answer 26

Correctly detecting the features present in a visual display, but making mistakes about how the features are bound together

i.e. Someone shown blue H and red T but reports seeing a blue T and red H

Question 27

Gestalt Psychologists:

Answer 27

Suggested that organization of perception of visual world is contributed by perceiver

Explains why perception of a stimulus can differ from the stimulus itself

Ie. Necker cube
Hand drawn cube that can be viewed in 2 different ways (reversible)

Question 28

Figure/Ground Organization:

Answer 28

Determination of what is the figure (object) and what is the ground

Question 29

Proximity/Similarity:

Answer 29

Perception guided by principles such as proximity and similarity

If you see 2 objects that are close together and resemble each other, you assume these elements are part of the same object

Question 30

Perceptual Constancy:

Answer 30

We perceive the constant properties of objects in the world even though the sensory information we receive about these attributes changes whenever our viewing circumstances change
i.e. object getting bigger as you get closer, but still knowing that its is still the same size

Question 31

Size Constancy

Answer 31

Correctly perceiving the sizes of objects in the world despite changes in retinal image size created by changes in viewing distance

Question 32

Shape Constancy

Answer 32

Correctly perceive shapes of objects despite changes in the retinal image created by shifts in viewing angle

Question 33

Brightness Constancy

Answer 33

Correctly perceive the brightness of objects whether they’re illuminated by dim or bright light

Question 34

Unconscious Inference:

Answer 34

Unconscious calculation done to perceive elements correctly

Size of image on retina x distance between you and object = size

Also occurs for shape and brightness constancy

Is the reason you misinterpret optical illusions

Question 35

Binocular Cues:

Answer 35

Distance Cues

Binocular Disparity

Question 36

Distance cues

Answer 36

Features of stimulus that indicate an object’s position

Question 37

Binocular disparity

Answer 37

Difference between 2 eyes’ views

Provides info about distance relationships in the world

Question 38

Monocular Cues:

Answer 38

Depth cues that depend only on what each eye sees by itself

Depends on adjustment that the eye must make to see the world clearly
Lots of adjustment for nearby objects, little adjustment for objects far away

i.e. Pictorial cues

Question 39

Pictorial cues

Answer 39

Creating an impression of depth on a flat surface (i.e. in pictures)

Interposition

Linear Perspective

Question 40

Interposition

Answer 40

Blocking of your view of one object by another object

Question 41

Linear Perspective

Answer 41

Pattern in which parallel lines seem to converge as they get farther and farther away

Question 42

Motion Parallax

Answer 42

Projected images of nearby objects move more than those of distant ones

Question 43

Optic Flow

Answer 43

Pattern of stimulation across visual field also changes as you move toward object