Week 5 - Sensation And Perception

Question 1

What is sensation?

Answer 1

The process by which the sense organs (eg. Eyes, ears, skin etc) gather information about the environment

No 1:1 correspondence between physical and physiological reality

Question 2

What is perception?

Answer 2

The process by which sensory information is selected, organised and interpreted.

But there isn’t a 1:1 correspondence between physical and psychological reality (sensation and perception).

Question 3

Describe transduction

Answer 3

(Environmental) energy -> neural impulses

Coded in terms of

• intensity
• quality

Sense receptors “transduce” stimuli into signals

Sensory adaptation

Question 4

Define psychophysics

Answer 4

Study of how we perceive sensory stimuli based on their physical characteristics

Question 5

Absolute threshold in psychophysics

Answer 5

Is the lowest level of a stimulus (on its own) that we can detect 50% of the time

• a candle 30km away
• 50 odorant molecules

Fechner’s model demonstrates the absolute threshold

Question 6

Just noticeable difference in psychophysics

Answer 6

Just noticeable difference is the:

-smallest change in intensity of a stimulus that we can detect

Depends on:

• level of intensity of new stimulus
• level of stimulation already present

Eg. Distinguish a quiet and a loud voice

Question 7

What is attention?

Answer 7

Mental phenomenon of concentration and it’s shifts in focus

• influences by external and internal events
• limited capacity

Question 8

What is selective attention?

Answer 8

Allows us to select some inputs for further processing and ignore others.
- reticular activating systems (RAS) and basal forebrain activate regions of cortex (eg frontal cortex).

Question 9

Bottleneck theory of attention in selective attention

Answer 9

Broadbent (1958) - bottleneck theory of attention

• early filtering mechanism (early selection model)
• limited capacity channel

Question 10

What does the cocktail party phenomenon suggest about selective attention?

Answer 10

Suggests some information gets through the filter.

Even when we selectively attend to a conversation we are subconsciously monitoring other conversations around us.

(Slightly refutes the bottleneck???)

Question 11

What’re some errors of attention?

Answer 11

Inattentional blindness: a failure to see something in plain sight

Change blindness: the inability to detect changes in scenes when looking directly at them

Question 12

What is divided attention?

Answer 12

Attention has a limited capacity.

Divided attention: performing multiple tasks simultaneously.

We really shift attentional resources between tasks. The faster and more efficiently we can make these shifts the better we can “multi-task”.

Question 13

What is considered one wavelength and wave amplitude?

Answer 13

Wave between two peaks. Amplitude height and it determines intensity.

We can only see a very small part of the light spectrum.

Question 14

Parts of the eye. (Basic)

Answer 14

Sclera (white part)
Pupil (light comes in)
Iris

Question 15

What’re the two processes of the eye inside ?

Answer 15

1. Focussing light on retina

2. Transfixing the image into nerve signals

Question 16

Features of photoreceptors

Answer 16

Photoreceptors (Rods and cones) turns light energy into electrical signals

Electrochemical process mediated by photo pigments

• rods use rhodopsin
• light bleaches rhodopsin causing fatigue (leads to “after” images like after you turn away from an illusion you feel like you can still see it)

Question 17

Describe the photo receptors (rods and cones)

Answer 17

Rods:

• low light
• monochromatic
• peripheral vision

Cones:

• bright light
• colour vision
• central vision (fine detail)

Question 18

Photoreceptors to ganglion cells

Answer 18

Convergence to rods and cones

Light comes in ->Retinal ganglion cell -> amacrine cells -> bipolar cells ->horizontal cells -> cone receptors -> Rod receptors/ back of the eyeball

Low convergence in come fed circuits
1 Retinal ganglion cell -> 1 bipolar cell ->1 cone

High convergence in Rod fed circuits
Multiple Retinal ganglion call -> multiple bipolar call -> multiple Rod

Question 19

GET COMFORTABLE WITH THE PRIMARY PROJECTION PATHWAYS OF THE VISUAL SYSTEM

Answer 19

Yay

Question 20

Describe parts of the visual cortex

Answer 20

Different cortical cells respond best to different stimuli.

Simple cells: light if specific orientation at a particular location

Complex cells: specific orientation but less dependant on location

Feature detectors: lines and edges (simple/complex cells), length of lines, shapes, movement, colour etc.

Question 21

Diagrammed parts of the occipital lobe.

Answer 21

Separated info colours
V1/Primary part of the visual cortex
V4 for colour

Question 22

What is colour vision?

Answer 22

Different theories explain different aspects of colour vision: opponent and trichromatic theory.

The two theories have BOTH been shown to be correct.

Question 23

What is one theory of colour vision?

Answer 23

Trichromatic theory: colour vision is based on our sensitivity to three primary colours

• explains colour blindness
• consistent with three types of cones in eyes

Question 24

What is the opponent process theory of colour vision?

Answer 24

Colour vision as a function of complementary, opposing colours

• red vs. green
• blue vs. yellow
• black vs. white??

Activated vs. inhibited.

Question 25

Causes of blindness and percentage worldwide

Answer 25

Cataract 47.8% people worldwide treatable.

Glaucoma 12.3% treatable

Macular degeneration 8.7% not treatable

Diabetic retinopathy 4.8% not treatable

Childhood blindness 3.9% some types are treatable.

Question 26

Outline colour blindness

Answer 26

3 types

• monochromacy
• dichromacy
• (anomalous) trichromacy

Most usual cause is faulty cone development
-genetics: far more common in males

Can also be produced by physical or chemical damage to the eye, optic nerve, or cortical visual processing areas.

Question 27

What is one test of colour blindness?

Answer 27

Ishihara test. Letters in coloured pictures.

Question 28

Motion blindness and visual agnosia

Answer 28

Motion blindness (akinetopsia) - inability to perceive motion (or stick together the incoming images)

Visual agnosia- inability to recognise objects, despite normal ability to describe the shape and colour etc (deficit in what pathway)

Prosopagnosia (face blindness)

Question 29

Cortical blindness and blindsight

Answer 29

Weiskrantz (1986) - cortically blind people asked to

• identify shapes
• identify location

Individuals often claim they can’t do the task because they can’t see. Yet they perform these tasks at above Chance levels. Suggest there are some other elements of the visual system that allows people to operate.

Question 30

What is Weber’s Law in psychophysics?

Answer 30

Regardless of the magnitude of two stimuli, the second stimulus must differ from the first by a constant proportion for it to be perceived as different.
The Weber fraction for weight is 1/50 for the average person.

For example: 1 blueberry = 1 gram
Therefore 50 grams of blueberries to 100 grams of blueberries

Question 31

What is the signal detection theory in psychophysics?

Answer 31

Sensation occurs when we judge whether a stimulus is present or not

Two processes co tribute to signal detection:

1. Initial sensory process - sensitivity to the stimulus (signal to noise ratio)
2. Decision process - the individuals readiness to report detecting a stimulus when uncertain (response bias)

Question 32

Brightness and hue

Answer 32

We perceive brightness (intensity) and hue (colour)

• mixing lights produces white (additive)
• mixing pigments produces black (subtractive)

Question 33

What do the lens inside the eye do?

Answer 33

Transparent disk that focuses light rays for near or distant vision

Question 34

What does the cornea inside the eye do?

Answer 34

Curved, transparent dome that bends incoming light

Question 35

What does the iris do?

Answer 35

Coloured area containing muscles that control the pupil

Question 36

What is the pupil?

Answer 36

Opening in the centre of the iris that lets in light

Question 37

What’s the eye muscle

Answer 37

One of six surrounding muscles that rotate the eye in all directions

Question 38

What does the retina do

Answer 38

Innermost layer of the eye, where incoming light is converted into nerve impulses

Question 39

What is the optic nerve in the eye?

Answer 39

Transmits impulses from the retina to the rest of the brain

Question 40

What is the fovea at the back of the eye? (Point of central focus)

Answer 40

The part of the retina where light rays are most sharply focused

Question 41

What is myopia and hyperopia?

Answer 41

Nearsighted and farsighted eyes. Nearsightedness or farsightedness results when light is focussed in front of or behind the rear of the eye, respectively.