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PSYC323 > Week 1- Introduction to Sensation and Perception > Flashcards

Week 1- Introduction to Sensation and Perception Flashcards

1
Q

What are two opposing theories on how we perceive the world?

A

-The belief that our perception is entirely driven by internal factors (our brain) not on reality

Versus…

  • Naïve realism: the belief that we experience the external world exactly as it is and the way we do this is through the senses. The perceptual experience is like an impression or copy of the external object
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2
Q

Is naïve realism dependent or independent of the mind?

A

Mind independent

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3
Q

What are two examples in which we do not perceive the physical world as it actually is? What theory of perception does this contradict?

A

-Hallucinations
-Optic illusions

Contradicts the idea of Naïve realism: there must be some internally generated component to perception

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4
Q

Who is considered a founder of Naïve Realism?

A

Aristotle

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5
Q

What was Galileo’s beliefs on perception?

A

An object/ it’s properties only exists in consciousness. If a person isn’t there to perceive it it does not exists. This means perception is entirely subjective.

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6
Q

What is Dualism?

A

-Dualism operates on the idea that there is a mind-body distinction.
-It attempts to answer the question as to how the brain can give rise to inner mental life.
-There are two ‘parts’: the non physical part is the “mental substance” (mind/ soul/ consciousness). The physical part is the “extended substance” (material entities)

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7
Q

What ethical issues does Dualism give rise to?

A

Rene Descartes believed that only humans had the “mental substance” component (i.e. consciousness/soul). Therefore, in his mind animal’s cannot perceive pain and so cruelty and experimentation on animals was allowed.

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8
Q

What is a theory distinct from Dualism?

A

Monism: there is no spilt only a single entity invovled in perception (of both internal and external stimuli). This entity is the brain.

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9
Q

What are two reasons why Monism became more popular as an explanation for how we perceive the world?

A

-Influence of religion decreasing (Darwinism coming in)
-knowledge on the complexity of the nervous system is expanding

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10
Q

What happened in the 20th century in terms of views around the brain’s role in perception?

A

-Experiments using advancing technology (neurology, neurosurgery, neurosurgery) allowed for a casual role of the brain in perception to be confirmed

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11
Q

What does sensation require?

A

A physical force

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12
Q

What does perception require?

A

The nervous system (make’s sense of the physical force)

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13
Q

What is an example of the brain generating perception without external triggers?

A

Imagination

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14
Q

Is dualism completely dead in today’s world?

A

No

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15
Q

What is the difference between sensation and perception?

A

-Sensation: Physical process, receiving stimuli from the environment via the
sensory systems
-Perception: Cognitive process, interpreting sensory signals into a conscious experience

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16
Q

What third process on top of sensation and perception is required?

A

-Recognition: Also a cognitive process – it’s identifying and/or categorizing our perceptions

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17
Q

What is signal transduction?

A

-Occurs between sensation and perception
-Involves taking the physical stimulus and changing it to neural signals

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18
Q

What is transmutation?

A

-Occurs between perception and recognition
-Involves transmitting, processing and integrating the biological (neural) activity to produce emergent physiological phenomena

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19
Q

What out of sensation, perception and recognition is modulated by cognition/ behaviour and what is the term for this?

A

-Perception and Recognition
-Top down processing

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20
Q

Who are two important people in the realm of psychophysics and what is this?

A

-Gustav Fechner and his mentor Ernst Weber
-Psychophysics is about linking physical stimuli and mental phenomena

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21
Q

What are the two key concepts of Gustav Fechner?

A
  • The absolute threshold (DETECTION) is
    the minimal limit of detection. i.e. the minimum stimulus that produces sensation 50% of the time (e.g. 0 dB for sound)

-The relative threshold (DISCRIMINATION)
is the minimal change in stimulus required to elicit a change in sensation 50% of the time i.e. you have a weight in your hand and are adding more weight what weight increase would result in you perceiving more weight

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22
Q

What is relative threshold (discrimination) now termed?

A

Just Noticeable Difference or JND

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23
Q

What is the Weber-Fechner law?

A

-The relationship between the stimulation
level and the perceived sensation is
proportional (% based)
-To detect a change in stimulus, intensity
must increase relative to the current level
-In other words, the larger the stimulus magnitude, the greater the amount of
difference needed to produce a JND.
-This is a logarithmic relationship!

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24
Q

What is an example of the Weber-Fechner law at play?

A

-If you picked up a 1 kg weight, would you notice if someone added an extra 1 kg to it? Yes

-If you picked up a 100 kg weight, would you notice if someone added an extra 1 kg to it? No

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25
Q

What is the Weber constant (k)?

A

A constant proportion of the initial stimulus value that represents the JND (Weber’s Law : Δ I / I = k)

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26
Q

How come the Weber constant (k) for touch varies?

A

-Depends on the location of the body that the touch occurs
-Depends on the kind of touch (e.g. pressure, pain, textures)

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27
Q

What is adaptation? What famous study illustrates this?

A

-Being consistently presented with one one kind of stimulus can change your perception of it
-Ekman et al. (1967). Adaptation to odour presentation. Perceived magnitude (intensity) over time if stimulus constantly present decreased and then upon stimulus withdrawal re- sensitization will occur (odour perceived as stronger again after break)

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28
Q

Why is adaption useful and why may it be not so useful?

A

-If working in uncomfortable environments such as where there is strong smells will become desensitized to it
-Not good at times where discomfort serves as warning of damage e.g. if you desensitized to hearing loud noises it may be more comfortable but they will still be doing damage to your hearing/ threshold for hearing higher due to desensitization and therefore you up volume to compensate causing more damage?

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29
Q

What does it mean to be a psychophysicist?

A

To quantitively study how environmental stimuli get converted into psychological experiences

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30
Q

List Fechner’s three methods to determine thresholds…

A

1) Constant stimuli
2) Limits
3) Adjust

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31
Q

What is Fechner’s method of constant stimuli?

A

To determine absolute threshold:
-You present different stimuli in a random order
-Ask individuals if they detect the stimulus or not?

To determine the JND:
-stimulus standard versus comparison stimulus
-Is the other stimulus weaker, stronger or the same strength?

32
Q

Does the threshold always have to be set at where you can detect the stimulus/ difference 50% of the time?

A

No, this is just the convention. This can be changed depending on what the researcher wants i.e. 75%

33
Q

What is Fechner’s method of limits?

A

To determine absolute threshold:
-Present stimuli in order (ascending/ descending)
-The participant tells you when they can detect the stimulus

To determine the JND:
-present standard stimuli with a comparator stimuli going in ascending value
-Tell when the comparator goes from weaker compared to the standard to stronger

34
Q

What is Fechner’s method of adjustment?

A

To determine absolute threshold:
-adjust the stimulus until you just detect it e.g. turning up a volume dial

To determine the JND:
-standard stimulus provided
-adjust the comparator stimulus until it matches the standard
-magnitude of variance= the JND

35
Q

What is the shortcoming of all three of Fechner’s methods of detection?

A

How can we be certain we are just measuring sensitivity to the stimulus:
-doesn’t take into account bias i.e. if we are actually looking out to hear something we are more likely to hear it so a threshold may not reflect the real world
-there is an issue with the signal to noise ratio. Laboratory setting will reduce noise to a far greater degree than real life.

36
Q

What is an alternate school of thought that overcomes some of the problems with Fechner’s model of detection?

A

Signal detection theory

37
Q

Draw a table of the four possible options that come out of a signal detection experiment… what is the four part score made up of?

A

-answer in slides
-4 part score= % hits + % misses + % correct rejection + % false alarms

38
Q

In a signal detection experiment what is sensitivity?

A

Is the ability to tell the difference between a signal and noise

Sensitivity comes from getting a measure of the proportion of ‘hits’ vs ‘false alarms and ‘miss’ vs ‘correct rejections’ (i.e. from the percentage of correct responses)

39
Q

What is d’ in terms of signal detection theory?

A

-d’ is a measure of how different the signal is from the noise (the strength of the signal)
-more noise/ weaker signal= smaller d’
-d’ therefore informs an individuals ability to detect signals (informs sensitivity) and it is something an experiment can manipulate!

40
Q

What is bias in a signal detection experiment?

A

Bias is if a participant is motivated for some reason to say yes or no irrespective of the signal they are trying to detect

41
Q

What letter represents bias in the realms of signal detection theory?

A

-Criterion B
-This indicates the ‘threshold’ for saying yes or no (motivation in either direction)

42
Q

What is the term is someone is bias towards saying yes in a signal detection experiment? What is the result of this?

A

-Liberal
-Increase in both hits but also in false alarms
-Criterion B (the threshold to say yes) will go down/ move to the left in a graphic

43
Q

What is the term is someone is bias towards saying no in a signal detection experiment? What is the result of this?

A

-Conservative
-Increase in miss and correct rejections
-Criterion B (the threshold to say yes) will go up/ move to the right in a grahpic

44
Q

Does bias effect sensitivity?

A

-Sensitivity and bias are independent of each other
-This is because as bias creeps in both categories of yes (hit and false alarms) increase proportionately

45
Q

Why is signal detection theory useful as opposed to Fechner’s three methods for threshold determination?

A

takes into account two things
-sensory capacity/ sensitivity to stimulus: psychophysical data
-participants criterion/ how likely are they to say yes (bias) : psychological data

46
Q

What are some things that effect bias/ willingness to say yes in a signal detection experiment?

A

-prior knowledge
-attention
-age
-sensory noise
-motivation

47
Q

In a signal detection experiment by Riekki et al, 2013 what was shown about the difference in skeptics and believers in paranormal activity?

A

-Gave individuals an illusory face perception task (do you see a face?- out of bunch of rubber bands and cups)
-Found believers are far more likely to respond “yes” (detect patterns in noise) but only because of increased bias- not sensitivity!
-In other words believers in paranormal activity were liberal responders in this task

48
Q

What is more common now Fechner’s methods for signal detection or signal detection theory?

A

signal detection theory

49
Q

How is manipulation useful in terms of signal detection theory?

A

-We can manipulate criterion to test effects on psychometric function
- Can use to parse out psychometric (sensitivity) from psychological data (bias: criterion B), or test the relationship between the two
-there is always going to be bias sometimes it is better to use it to your advantage instead of trying to eliminate it

50
Q

What is magnitude estimation?

A

-Present a participant with a stimulus and ask them to rate it’s magnitude
-The scale they use can either be numerical or non numerical

51
Q

What is the steven’s power law?

A

-Builds on Weber-Fechner principles
-Based on magnitude estimation (0-100)
-Perceived magnitude increases nonlinearly at different rates in different sensory modalities (all relative to the exponent)
-the same data can be plotted on a logarithmic axis and - perceived magnitude now increases linearly, showing a power-law relationship between stimulus intensity and perceived magnitude

52
Q

Why is it useful that perceived magnitude increases at different rates for different sensory modalities?

A

taking an electric shock as an example we want relatively small increases in shock to produce larger and larger adverse reactions in order to protect us from raising voltage too much and causing harm

53
Q

What is cognitive neuroscience?

A

Attempts to map neural phenomena to psychological processes

54
Q

What are dermatomes?

A

particular areas of the body where peripheral nerves (spinal + cranial) are sent out to

55
Q

What is nerve? What is a tract?

A

-Nerve= bundle of axons in PNS
-Tract= bundle of axons in CNS

56
Q

What are ganglia? What are nuclei?

A

-Ganglia= Clusters of cells in the PNS
-Nuclei= Clusters of cells in the CNS

57
Q

What two forms can receptors exist as? How will they be distinguished in this course?

A

-Receptors can either be proteins on the surface of a cell or they can be the cell itself
-In this course…
sensory receptor neurons= cell
sensory receptor protein= protein

58
Q

What are the three key features of sensory receptor neurons?

A

-Always found in sense organ
-Always react to some kind of signal from the environment (physical or chemical) don’t react to signals from other neurons!
-Perform signal transduction (convert one form of signal to a different type of signal)

59
Q

What is the function of the human nervous system broadly speaking?

A

-Receive info from the environment via the sensory systems
-Process and integrate that info in the brain
-Plan and execute a response via the motor systems

60
Q

What sensorimotor loop occurs in the human nervous system?

A

-There is constant feedback from the sensory systems that is vital to update and inform motor activity
-This is that we can respond appropriately= essential for survival!

61
Q

Why might the tradition 5 senses not be good enough?

A

-Categories like touch/ somatosensation are so broad including things like pain, itch, heat. This begs the questions as to whether some of these subfields should be classed as their own independent modality
-These modalities don’t necessarily cover everything i.e. Balance (the vestibular sense) There might not be enough categories.

62
Q

What are the four criteria for something to be classed as a sense?

A

1) specialized to receive a particular stimulus
2) Performs signal transduction (stimulus → neuronal potential)
3) Relays the neural signal to the brain via certain pathway (synapse 1 → synapse 2 → synapse 3 …)
4) Has its own cortical region for processing (sensory cortices + association cortices)

63
Q

What is a problem that arises from all sensory signals being converted to electrical brain signals?

A

How do we interpret different sensations if all they become in the brain is action potentials (they all operate on the same ‘currency’)

64
Q

What is Muller’s Doctrine of Specific Nerve Energies (1842)?

A

Argues that the 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

65
Q

What is the theoretical problem of Muller’s Doctrine of Specific Nerve Energies (1842) to explain differences in perceiving senses? What is the ‘solution’ to this?

A

-Brain stimulation can elicit sensation WITHOUT nerve conduction! * e.g. Penfield’s stimulation studies (1940s)
-Thus, each modality must have independent sensory cortices
as mentioned

66
Q

What does having independent sensory cortex’s allow for in terms of identify senses?

A

Means that at the cortex level can distinguish where information is coming from/ what sense

67
Q

If stimulus → action potential → nerve tract → sensory cortex, then how do we get different qualities (sub modalities) within a
sense?

What is this problem called?

A

univariance

e.g.
odorant - action potential - olfactory nerve - olfactory cortex = onion smell

odorant - action potential - olfactory nerve - olfactory cortex = cinnamon smell

Two different odors cause the same pattern of activity in the brain but then somehow result in different perceptions of the smell

68
Q

If you only have one ‘currency’ to work with (action potential), how do you represent all the diverse qualities of the world?

A

-There needs to be an encoding scheme
-Pattern of action potential/ activity in portion of the cortex create representations

69
Q

List the three types of encoding schemes…

A

-Specificity coding
-Population coding
-Rate coding

70
Q

What is specificity coding?

A

-Qualities are represented by activation
of specific neurons e.g. the Jennifer Anniston cell
-Stimulus is known as having a labelled line

71
Q

What is population coding? what does it allow for?

A

-Qualities are represented by the pattern of activity across a group of neurons
-This allows for fair fewer neurons to be associated with representations and therefore, less space in the cortex needs to be devoted to this (More efficient)

72
Q

What is rate coding?

A

– qualities are represented by the firing rate of the neuron
-Useful for coding stimulus intensity
-Useful for coding stimulus duration

73
Q

Does rate coding happen the single cell level only or can it happen at the population level also?

A

Can happen at both levels

74
Q

Do our neural representations reflect complete data?

A

-No, combining incoming sensory data with existing data (memory) gives us the best guess of what’s likely to be generating the sensory data
-Perception= inference

75
Q

What is the rubber hand illusion and what does it show?

A

-Start by having a person place there hand below a table and then have a rubber hand onto of the table roughly where it should be
-Have a brush tickling the rubber hand and just touching the hand below the table
-Individual will start to think based on inference that the hand on the table is theirs despite not getting the sensory info of touch to inform them they are being tickled
-When stab the rubber hand will have sudden shock/ pain reaction which is reflected in EEG traces of brain activity.
-Shows that a lot of what we perceive is based on inference/ top down processing

76
Q

Overall what is the message about how the brain perceives the world around us?

A

We construct our own reality and it’s hard to know whether what we perceive is universal (common to everyone) or individual to us

77
Q

Is sensory research only quantative?

A

No, can be qualitative as well. Qualitative research has a place in trying to get self reports of people’s sensory experiences/ if you want want to compare accounts

PSYC323 (21 decks)

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