Chapter 4 - Sensation and Perception

Question 1

Sensation

Answer 1

Detection of physical energy by the sensory organs

Raw “bottom-up” processing of info from outside world

Question 2

Transduction

Answer 2

The process of translating external stimuli into the “language of the brain”.

Question 3

Perception

Answer 3

• Brain’s stable and meaningful interpretations of the sensory organ input
• Higher order “top-down” processing that involves memory, previous experience, context, etc.

Question 4

Define: Parallel processing

Answer 4

• We use a combination of both sensation and perception processes to experience “reality”
• Using many sense modalities simultaneously

Question 5

Five common traits of transduction

Answer 5

1. Specialized: Each sense has specialized cells
2. Strength: Change in neuron firing rate depends on strength of stimuli
3. Adaptation: Sensory adaptation; activation is greatest when stimulus first detected
4. Organized: At each stage of processing sensory receptors are highly organized.
5. Threshold

Question 6

Psychophysics

Answer 6

• A sub-field within sensation/perception area
• Researchers attempt to describe quantitatively the transition from stimulus to experience
• “General laws that apply for most people across all kinds of sensory input?”
• “How intense (bright, loud, hot) does a stimulus have to be in order to sense/perceive it” eg, how far can you see candle at night?

Question 7

Absolute Threshold

Answer 7

• The intensity level at which most people detect stimulus 50% of the time.
• Eg, candle flame at 48km; watch tick at 6m

Question 8

Just Noticeable Difference (JND)

Answer 8

Smallest detectable difference in magnitude between two stimuli that we can detect

Question 9

Factors affecting individual’s response to JND

Answer 9

TEMPS

• Tired/alert
• Expectations (eg, perceptual sets)
• Motivation to detect
• Previous experience
• Strength of stimulus

Question 10

Signal Detection Theory (SDT)

Answer 10

• Noticing a stimulus against background “noise”
• Assessing potential gain/loss associated with your decision
• (ie, in response to intermittent very dim light: hit, false alarm, miss, correct rejection)

Question 11

Examples of selective attention

Answer 11

• Dichotic listening task (Donald Broadbent; tuning out different messages in each ear)
• Shadowing: mixing of two incomplete messages to form coherent whole
• Cocktail party effect: Hearing your own name

Question 12

Three components of visual system (A,B,C)

Answer 12

• Visual Transduction (light enters eye, tansduced into neural messages)
• Extracting sensory messages from light (how eyes relay info to brain)
• Producing stable interpretations of visual input (identify objects, perceive motion, depth, perceptual constancies)

Question 13

Visible Light

Answer 13

400-700 nM part of electromagnetic spectrum

Question 14

Fovea

Answer 14

Fovea: point of central focus; contains all of the cones

Question 15

Some reasons pupil dilates

Answer 15

• “pupillary reflex”
• Doing something complex
• Finding someone attractive

Question 16

Path taken by light

Answer 16

Cornea–pupil–lens–retina

Question 17

Define: Blind spot

Answer 17

Where optic nerve connects to retina

No rods or sense receptors

Question 18

Long & skinny lens can detect

Answer 18

Distant objects

Question 19

Short & fat lens can detect

Answer 19

Close objects

Question 20

Myopia

Answer 20

Near-sightedness

Cornea too round or eyes too long (horizontally)

Question 21

Hyperopia

Answer 21

Far-sightedness

Cornea too flat or eyes too short (horizontally)

Question 22

Presbyopia

Answer 22

Lens loses elasticity as we age; loses ability to focus on close objects

Question 23

Cones

Answer 23

• Short and round
• 6 million on retina (fovea)
• Day-light vision
• Colour vision/fine detail/high spacial acuity
• Packed in fovea

Question 24

Rods

Answer 24

• Slender and cylindrical
• 120 million on retina
• Dim-light vision (night)
• Shades of grey/low spatial acuity
• None in fovea

Question 25

Rhodopsin

Answer 25

• Photo pigments in rods
• Gets bleached; takes 20-30 min to re-sensitize
• In green leafy veg, some in carrots

Question 26

Define: two theories of how we perceive colour

Answer 26

1. Trichromatic Theory:
   - Young-Helmholtz
   - Three types of cones, each sensitive to red, green, or blue
2. Opponent Process Theory:
   - Three types of cones sensitive to complimentary colours
   - yellow/blue; red/green; black/white

Question 27

Define: Bottom-Up Processing

Answer 27

Perception controlled by physical messages delivered to the senses; whole is constructed from parts

Question 28

Top-Down Processing

Answer 28

Perception controlled by one’s beliefs, experiences, expectations; imposed on raw stimulus

Question 29

Gestalt Principles of Visual Organization

Answer 29

-Rules governing how we perceive objects within their overall context

Question 30

Define following monocular depth cues:
Motion Parallax
Interposition
Light & Shadow
Relative Size
Texture Gradient
Height in Plane
Linear Perspective

Answer 30

Distant objects move slower; closer move faster
Closer object blocks view of object behind
Object cast shadow, showing 3D form
Distant objects look smaller
Distant objects have less apparent texture
Distant objects appear higher
Outlines of rooms/objects appear to converge in distance

Question 31

Monocular Depth Clues

Answer 31

Require input from only one eye

Question 32

Define following binocular depth clues:
Binocular disparity
Convergence

Answer 32

Difference between location of images in each retina

How far the eyes turn inward to focus on moving object

Question 33

Sclera

Answer 33

White of the Eye

Question 34

Retina

Answer 34

Lines inside back of eye; light sensitive, creating neural impulses; thin as onion skin

Question 35

Lens

Answer 35

Contains muscles that change shape to focus, called accommodation.

Question 36

Iris

Answer 36

Colour; made up of muscles that constrict and dilate

Question 37

Pupil

Answer 37

Black middle. Pupillary Reflex decreases the amount of light entering the eye.

Question 38

Cornea

Answer 38

Bends light onto pupil. Where light enters the eye.