Visual perception

Question 1

Function of the iris

Answer 1

Pigmented membrane with a central opening (pupil). Regulates amount of light on retina by adjusting size

Question 2

Function of the lens

Answer 2

refracts light and focuses it on the retina by altering its shape according to the distance of objects focused on

Question 3

Function of the Cornea

Answer 3

Refracts light

Question 4

Function of the Retina

Answer 4

the innermost layer of the eye, which is composed of several layers of specialised cells that convert light into neural signals.

Question 5

Function of the Fovea

Answer 5

contains highest density of cones. Point of sharpest vision (100% visual acuity).

Question 6

Function of the optic nerve

Answer 6

contains a bundle of ganglion axons that carry visual information to the lateral geniculate nucleus (LGN) of the thalamus.

Question 7

Describe reception

Answer 7

detection of light energy by the sensory receptors of the retina

Question 8

Process of reception

Answer 8

1. light waves enter the eye
2. The cornea refracts the light waves to focus them on the retina
3. light travels through the pupil, and the iris regulates the amount of light that enters the eye via the pupil
4. the kens further refracts the light waves to focus on the retina
5. the photo receptors of the retina detect the light stimulus

Question 9

Describe transduction

Answer 9

is the conversion of stimulus energy (light) into impulses of electrochemical energy by sensory receptors of the retina

Question 10

What are the two types of specific features of light that photoreceptors respond to

Answer 10

Retinal rods, retinal cones

Question 11

On center receptive fields

Answer 11

stimulated by light falling on the center of the receptive field and inhibited by light falling on the periphery

Question 12

off center receptive field

Answer 12

stimulated by light falling on the periphery of the receptive filed and inhibited by light falling on the center

Question 13

describe transmission (Step 4)

Answer 13

electrochemical impulses due to stimulus received via optic nerve
optic nerve exits retina at blind spot
optic nerve cross over as optic chiasm
Info then travels to primary visual cortex in occipital lobe (optic radiation)

Question 14

describe organisation (Step 5)

Answer 14

All visual stimulus is organised
occipital lobe relies on application of visual perception principles (learnt rules our brain automatically uses to interpret visual info)
allow for perception of visual info

Question 15

describe interpretation (Step 6)

Answer 15

Visual stimulus is given meaning
stimulus is assigned a meaning and is influenced by biological, psychological and social factors
Once organised they are sent along one of two different pathways
1. parietal lobe: where pathway, judging where object is
2. temporal lobe what pathway, comparing information to already stored info

Question 16

Order of steps

Answer 16

reception
transduction
transmission
selection
organisation
interpretation

Question 17

describe physiology influence on visual perception

Answer 17

damage or misinformation of the visual system causes changes in perception of visual stimulus
examples are:
- astigmatism: partial fuzziness due to more the one focal point
- pressure build up in aqueous humour: damage to blood vessels = vision loss

Question 18

describe the ageing influence on visual perception

Answer 18

age causes many visual disturbances
examples:
- Presbyopia: lens becomes less elastic, less focus on close objects due to image converging after retina
- cataracts: progressive clouding of lens, due to protein build up (severe vision impairment)
- macular degeneration: most common cause of blindness, metabolic waste accumulates and attacks macular causing diminished central vision acuity

Question 19

how does genetics effect visual perception

Answer 19

disorders caused by genetics
examples:
- retinitis pigmentosa: degenerative disease of the retina (night blindness/gradual vision loss), retina dies, inherited
- colour vision deficiency: inability to detect colour normally, results to changes to functioning of the cones (red blue green) in retina

Question 20

What are the factors that contribute to perceptual sets

Answer 20

past experience, motivational state, emotional state, context

Question 21

what are the perceptual constancies

Answer 21

size constancy, shape constancy, orientation constancy, brightness constancy

Question 22

describe Gestalt principles

Answer 22

The tendency of our visual system to see things as a meaningful whole. Our brains can interpret the whole more easily than its parts.

Question 23

what are the 5 gestalt principles

Answer 23

Figure-ground organisation
continuity
closure
similarity
proximity

Question 24

what are binocular depth cues

Answer 24

retinal disparity: each retina giving slightly different images due to separation of eyes and angle of view. Brain merges two images. Bigger the disparity the closer the object
convergence: eyes converge when looking at close objects and diverge at further away objects, greater the angle of convergence the closer the object.

Question 25

What are the monocular depth cues

Answer 25

accommodation: eyes change focus as an object moves closer, to focus an image the lens must change, the ciliary muscle measures amount of accommodation required

Question 26

what are the pictorial depth cues

Answer 26

linear perspective - parallel lines appear to meet
interposition - overlapping an object makes it look further away
texture gradient - closer objects have better definitions then ones further away
relative size - when familiar with size of an object, the object that is bigger appears closer
height in the visual field - objects closer to the horizon are perceived to be further away
motion parallax - when moving objects closer seem to fly past whereas further away objects appear to move slower