sensation & perception, psychophysics

Question 1

sensation

Answer 1

Physical process - receiving stimuli from the environment via the sensory systems

Question 2

perception

Answer 2

Cognitive process - interpreting sensory signals into a conscious experience

Question 3

internalist

Answer 3

assumes that perceptions of objects (in the environment), and knowledge or beliefs about those objects, are aspects of a person’s mind

Question 4

externalist

Answer 4

Objects/observations etc constitute real aspects of the world, i.e. a true representation of the world.

Question 5

naive realism

Answer 5

our perception = how the objects actually are

Question 6

arguments against naive realism

Answer 6

1. humans have cognitive biases which can distort their perception of reality.
2. theory of relativity, which states that our perception of space and time are not objective realities but creations of our minds.

Question 7

john locke on perception

Answer 7

2 stages for perception

• direct perception of the object
• internal representation of the object

In sum: perceptual experience of an object is a copy of the object’s primary qualities, mixed with subjective elements caused by the observer.

Question 8

dualism

Answer 8

• mind = non-physical, conscious
• body = material substance, physical

Question 9

monism

Answer 9

brain gives rise to perception from internal plus external stimuli

Question 10

functions of CC

Answer 10

• perceptual-motor functions (i.e. coordinating the hands in space)
• sensory-perceptual functions (i.e. unifying the two visual fields of space)

Question 11

absolute threshold

Answer 11

The minimal limit of detection. i.e. the minimum stimulus that produces sensation 50% of the time

Question 12

relative threshold

Answer 12

The minimal change in stimulus required to elicit a change in sensation 50% of the time (= Just Noticeable Difference or JND)

Question 13

Weber-Fechner law (in words)

Answer 13

The just noticeable difference (JND) between 2 stimuli is a function of the magnitude of the original stimulus

The larger the stimulus magnitude, the greater the amount of difference needed to produce a JND

Question 14

Weber constant (k)

Answer 14

a constant proportion of the initial stimulus value that represents the JND

Question 15

Weber’s Law

Answer 15

Δ I / I = k

Question 16

low k means…

Answer 16

…good at detecting difference

Question 17

adaptation

Answer 17

Perceived magnitude (intensity) decreases over time if stimulus constantly present

Only when stimulus changes or is removed does our perceived intensity change

Question 18

Fechner’s 3 Methods - list

Answer 18

1. constant stimuli
2. limits
3. adjustment

Question 19

Constant Stimuli to determine absolute threshold:

Answer 19

set of stimuli presented multiple times, random order - do you detect?

Question 20

Constant Stimuli to determine JND:

Answer 20

standard stimulus vs comparison stimuli (multiple times, random order) - weaker/stronger/same?

Question 21

Limits to determine absolute threshold

Answer 21

stimuli in ascending order - when do you detect?

Question 22

Limits to determine absolute threshold

Answer 22

stimuli in ascending order vs constant stimuli - when does it change from weaker to stronger?

Question 23

Adjustment to determine absolute threshold

Answer 23

adjust the stimulus until you can just detect it (like using a dial)

Question 24

Adjustment to determine absolute threshold

Answer 24

adjust until it matches the comparison stimuli

Question 25

D prime in signal detection theory

Answer 25

measures perceptual sensitivity
- Difference between the mean amount of sensory activity generated by the noise alone trials and the signal+noise trials will equal sensitivity (d’)
= hits - false alarms

Question 26

bigger d’ means

Answer 26

stronger signal or less noise (easier to detect)

Question 27

Criterion (β) in signal detection theory

Answer 27

Y/N bias

Question 28

Yes bias =

Answer 28

• shifted criteria left
• increases proportions of hits and false alarms
• -ve C

Question 29

3 laws of qualia - list

Answer 29

1. irrevocability
2. flexibility
3. endures ST memory

Question 30

irrevocability

Answer 30

once the qualia is perceived, it cannot be denied or changed [the input side]

Question 31

flexibility

Answer 31

you can interpret the perception of something in the world in a multitude of ways [the output side]

Question 32

Endures in short term memory

Answer 32

need to be able to hold the representation of the qualia in short term memory to perceive it

Question 33

Stevens’ Power Law

Answer 33

• Based on magnitude estimation (0-100)
• perceived magnitude increases nonlinearly at different rates in different sensory modalities
• log = linear increase ⇒ power-law relationship between stimulus intensity and perceived magnitude

Question 34

Müller contribution to the field of sensation and perception.

Answer 34

• Muller’s Doctrine of Specific Nerve Energies (1842)
• brain distinguishes between different senses by monitoring activity in different sensory nerves
• e.g. anything that activates optic nerve will elicit ‘light’, anything that activates auditory nerve will elicit ‘sound

Question 35

Penfield contribution to the field of sensation and perception

Answer 35

• neurosurgeon, mapped the homunculus
• decussation and contralateral mapping (pathways cross midline)

Question 36

three neural encoding schemes

Answer 36

1. rate coding
2. specificity coding
3. population coding

Question 37

rate coding

Answer 37

qualities of a stimulus are represented by changes in firing rate

Question 38

specificity coding

Answer 38

qualities of a stimulus are represented by activation of specific neurons

Question 39

population coding

Answer 39

qualities are represented by the pattern of activity across a group/population of neurons

Question 40

criteria for a sensory system (4)

Answer 40

• Specialised to receive particular stimulus – i.e. has specific receptors for specific physical energy/chemical molecules
• Performs signal transduction (stimulus → neuronal potential)
• Relays the neural signal to the brain via certain pathway (synapse 1 → synapse 2 → synapse 3 …)
• Has its own cortical region for processing (sensory cortices + association cortices)

Question 41

problem of univariance (explanation and solution)

Answer 41

Q: all info enters brain as APs, so how do we get different modalities and sub-modalities?
A: different ways of coding - rate, specificity, population

Question 42

qualia

Answer 42

a quality or property as perceived or experienced by a person

the raw feel of sensations such as the subjective quality of “pain” or “red” or “gnocchi with truffles”