Chapter 4: Vision

Question 1

Visual acuity

Answer 1

The ability to see fine detail.

Question 2

Visible light

Answer 2

Lightwaves visible to humans.

Portion of the electromagnetic field that humans can see.

Question 3

Wavelenghts

Answer 3

The distance between successive peaks of a wave.

Question 4

3 PHYSICAL DIMENSIONS OF LIGHT: Lenght determines:

Answer 4

Hue (what we perceive as colour).

Question 5

3 PHYSICAL DIMENSIONS OF LIGHT: Amplitude determines:

Answer 5

Brightness

Question 6

3 PHYSICAL DIMENSIONS OF LIGHT: Purity determines:

Answer 6

Saturation or richness of colour

Question 7

Retina

1. What is it?
2. What does it do?

Answer 7

1. A layer of light-sensitive tissue lining the back of the eyeball.
2. Turns light waves into neural signals

Question 8

Accomodation:

Answer 8

The process where the eye maintains a clear image on the retina.

The muscles in the eye change the shape of the lens.

Flatter lends for further objects.

Rounder lends for nearby objects.

Question 9

Myopia (?)

Answer 9

Images are focused in the front the retina because the eyeball is too long or the lens is too rounded (?)

Question 10

Hyperopia (?)

Answer 10

Images are focused behind the retina because the eyeball is too short and the lens is

Question 11

Photoreceptors

Answer 11

Light-sensitive proteins that absorb light and transduce it into electrical signals.

Question 12

Cones

1. What does it do?
2. What are there concentrated?
3. What are the 3 types and what are they sensitive to?

Answer 12

1. Helps to focus on fine detail and to detect colour under normal daylight conditions.
2. They are concentrated at the fovea.
3. • L-cones: Sensitive to long wavelengths (ex. red).
   • M-cones: Sensitive to medium wavelenghts (ex. green)
   • S-cones: Sensitive to short wavelenghts (ex. blue, purple).

Question 13

How do the 3 cones determine brightness?

Answer 13

It is signalled by the total amount of activity across all three cone types.

Question 14

How do the cones interpret colour?

Answer 14

Colour is signalled by the relative levels of activity between pairs of cone types..

Question 15

Rods

Answer 15

Sensitivity to faint light in the periphery.

Activates in under low-light conditions, for night vision.

Question 16

Periphery

Answer 16

In the retina, it is the area outside the fovea.

Question 17

Fovea

Answer 17

The area in the retina where the cones are concentrated, allowing humans to see colour and fine detail. Area with the greatest visual acuity.
No rods at all.

Question 18

Bipolar cells

Answer 18

Collects electrical signals from the rods and cones and transmits them to the retinal ganglion cells (RGCs) in the outmost layer of the retina.

Question 19

Retinal ganglion cells

Answer 19

Organizes the electrical signals from the rods and cones and sends them to the brain.

Question 20

Optic nerve is formed by…

Answer 20

The optic nerve is formed by the bundle of the retinal ganglion cells’ axons.

Question 21

Blind spot

Answer 21

A location in the visual field that produces no sensation on the retina because of the optic nerve.

Quite a big hole, but our perceptual system automatically “fills in” using knowledge of the colour or texture around the blind spot.

Question 22

Action potentials containing information about visual information from the retina travel to the brain along the ____ ____ and goes to the _____ ____ ____ (LGN) located in the _______ of each hemisphere. Then, the visual information goes to the ____ __

Answer 22

optic nerve
lateral geniculate nucleus
area VI

Question 23

Colour deficiency (colour blindness):

Answer 23

A genetic disorder where one of the cone types and rarely, two.

Question 24

Colour afterimage

Answer 24

Sensory adaptation caused by staring too long at one colour that it fatigues the type of cone that corresponds to that colour.

Question 25

Colour-opponent system

Answer 25

Pairs of cones types work in opposition.

Explains colour aftereffects. If one is tired, and the other cone dominates, and another colour is perceived until the other cone rejuvenates.

Question 26

Visual receptive field

Answer 26

A single retinal is sensitive to a very small area of visual space.

Question 27

Info on V1 needed?

Question 28

Binding problem

Answer 28

The problem of how the brain links features together so that we see unified objects in our visual worlds rather than free-floating or miscombined features.

Question 29

Parallel processing

Answer 29

The brain’s ability to perform many activities at the same time.

Question 30

Illusory conjunction

Answer 30

A perceptual mistake whereby the brain incorrectly combines features from multiple objects.

Ex. When colour and shape is combined incorrectly.

Question 31

Feature-integration theory

Answer 31

The idea that focused attention is not required to detect the individual features of a stimulus (e.g., the colour, shape, size, and location of letters), but it is required to bind those features together.