Visual System and Perception

Question 1

How does the visual system work?

Answer 1

• Objects has energy(lights) that turns into nerve inpulses inside of the eye, and gets send to both of the hemispheres through the optic nerve
• The brain interpret the encodements from the receptors

Question 2

Pupil

Answer 2

Control the light, or adjust the eyes to the light

Question 3

Lens

Answer 3

Focus on objects to see something clearly, work with the retina

Question 4

Retina

Answer 4

Has several receptors that are sensitive to light

Question 5

Fovea

Answer 5

Has no rods but clusters of cones
- For accurate and precise vision

Question 6

Does our eyes work like a camera?

Answer 6

• We dont snap pictures like a camera does, the analogy does not hold up

Question 7

Transduction

Answer 7

Process of characteristics of stimulus to nerve impulses

Question 8

Normal stimulus

Answer 8

• Electro magnetic energy, from the environment
• The visible spectrum for humans are between 350nm - 800nm
• Different electromagnetic waves are perceived as different types of colors in our brains (their wavelenghts)

Question 9

Rods

Answer 9

• Sensitive to visible lights
• Black and white
• Prefer Dimlight

Question 10

Dark adaptation

Answer 10

Process of when our eyes gets used to dim lights
- Rods not always activated

Question 11

Cones

Answer 11

• Color receptors
• Sensitive to specific type of frequences of light
  Cones can be specialised
• Prefer bright lights

Question 12

How does the visiual transduction work?

Answer 12

Bipolar cells (pathways) to the optic nerve, use of photopigments
- Many rods are connected to the same bipolar cells
- Some cones has “private lanes” in Fovea

Question 13

Visual acuity

Answer 13

Ability to see fine details

Question 14

Change blindness

Answer 14

Failure to notice changes in visual stimuli when those changes happen during a saccade

Question 15

How does the eye move?

Answer 15

• Gets a sharp observation of only a small part of the environment
  Our “full picture” is an illusion, the brain predicts and/or fill in missing information
• Saccadic movements - rapid process, one point to another
• Fixations - pauses, takes in the info
  Notices visual stimuli like change in color
• Competing stimuli for attention, whats important to look at now?

Question 16

Intentional blindness

Answer 16

Failure to see an object we are looking at directly if our attention is elsewher
- A phenomena

Question 17

Trichromatic Theory - Basics

Answer 17

• Sensitive to different wavelenghts
• Cones have 3 different types
  If all are active, we see white
  Blue Green Red
• Missing or malfunction of cones gives color blindness

Question 18

Trichromatic Theory - Against

Answer 18

• Red-green blindness, but can still see yellow
• Cant explain after-images

Question 19

After image

Answer 19

Certain color stimuli presented and then withdrawn
- Sees the stimuli in different colors

Question 20

Opponent process theory

Answer 20

• Assumed 3 types of cones - 3 opposing systems
  1 type - 2 different wavelenghts
• We perceive a hue based on up to two colors at a time
• One color pair suppresses the other color
  Green supresses Red, hence why we cant see those mixed
• Explain after-images

Question 21

What are the color pairs in opponent process theory?

Answer 21

• Green or red
• Blue or yellow
• Black or white

Question 22

Dual process theory

Answer 22

• Three types of cones
  Based on wavelenghts (Trichromatic) - receptor (early stage)
• Signals from three color receptors combined before sent to the opponent cells (Opponent process) - brain (Later stage)
  Combines input

Question 23

Feature Detectors

Answer 23

Cell, specialised in visual stimuli
- Receive and integrate nerve impulses
Color, depth and movement

Question 24

What is color constancy?

Answer 24

Color seems relatively constant under varying illumination conditions
- Depends on light frequencies and prior knowledge
- Banana - Grey color

Question 25

How does depth perception work?

Answer 25

• The images in the retina is 2 dimensions
  Length + Width
• Brain creates a 3D image with help of
  Monocular depth cues
• Has more with 3D cues when it comes to images
  Binocular depth cues

Question 26

Monocular Depth cues

Answer 26

• There are 8 different types
  Parallel lines
  -Angle towards each other or to the middle
  Texture
• How it looks like on a distance
  Shadows
  Overlap
  Size of the object
• Distance judgements
  Movements - Parallax
• If we are moving, objects nearby moves faster than those futher away

Question 27

Binocular depth

Answer 27

• Combines info from both eyes
  Binocular disparity
• Each eye sees a slightly different image
  Image futher away from fixation points looks blurry

Question 28

Oculo-motor depth cues

Answer 28

• Limited to on object
• Binocular vision
• Consists of accomodation and vergence
  Holding a pen infront of you, eyes convergancing

Question 29

Accomadation

Answer 29

Lens changes its shape in order to bring an object in focus on the retina

Question 30

Vergeance

Answer 30

The process which the eyes move in equal and opposite directions of one another in order to fixate an object

Question 31

Convergence

Answer 31

Result of vergeance, eyes turning inwards in order to focus on an object

Question 32

How does perceptions of movement work?

Answer 32

• Complex process with info from several senses
• Identify or realize change of place of an object or body
• Getting info on speed and direction

Question 33

How does visual perception work?

Answer 33

• It encodes the visual information and make a selection
• Active and rapid

Question 34

Associative Agnosi

Answer 34

• Disrupts semantic access for object
  Cant associate objects with meanings
• Prior knowledge
• Can copy drawings but cant draw from memory or identify what they just drew