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PSYC 367 > L1-L3 > Flashcards

L1-L3 Flashcards

1
Q

Perceptual illusion

A

a difference between what is perceived and what is physically present in the world

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2
Q

Optical illusion

A

a difference between what is in the retinal image and what is physically present in the world

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3
Q

Sensation

A

the ability to detect a stimulus and turn that detection into a private experience

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4
Q

Perception

A

the act of giving meaning/purpose to those detected sensations

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5
Q

3 stages of the sensation process

A

physical stimulus, physiological response, sensory experience

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6
Q

Examples of techniques for studying the physiological response from a physical stimulus

A

animal single-unit recording, human brain imaging (e.g. MEG, PET, fMRI, ERPs)

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7
Q

Examples of techniques for studying the sensory experience from a physiological response

A

animal lesion studies, human clinical studies, human brain imaging

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8
Q

What is Fechner’s contribution to psychology?

A

invented psychophysics and believed to be the true founder of experimental psychology

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9
Q

Psychophysics

A

the science of quantifying the relationship between physical and psychological experiences

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10
Q

Just noticeable difference (JND)

i.e. difference threshold

A

the smallest change in a stimulus or difference between stimuli that can be detected 50% of the time

bigger JND needed for heavier standard weights relative to comparison

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11
Q

Absolute threshold

A

minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time

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12
Q

Psychometric function

A

a graph of stimulus value (e.g. intensity) on the horizontal axis versus the subject’s responses (e.g. proportion of “yes”) on the vertical axis

ogive or typical S shape

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13
Q

Weber’s law

A

the size of the JND or the difference threshold (△I) is a constant proportion (K) of the physical magnitude of the stimulus (I)

△I = KI

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14
Q

Fechner’s law

A

a principle describing the relationship between stimulus magnitude and the resulting sensation magnitude (i.e. scaling)

S = KlogR

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15
Q

What does Fechner’s law predict?

A

stimulus intensity increases more rapidly than sensation intensity (i.e. a larger change is needed to produce a JND in sensation as stimulus intensity increases)

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16
Q

Magnitude estimation

A

easier method for psychophysical scaling, wherein a participant assigns a number to describe stimulus intensity

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17
Q

What do magnitude estimation experiments show?

A

once detected, the sensory magnitude of a stimulus increases with its physical magnitude, within limits

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18
Q

Steven’s power law

A

the magnitude of subjective sensation (i.e. perceived intensity) is proportional to stimulus magnitude raised to an exponent (or power)

S = aI^b

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19
Q

2 possible reasons for the discrepancy between Fechner’s law and Steven’s law

A

assumption that all JNDs are perceptually equal (Fechner’s) is violated for some sensory modalities; magnitude estimation is more subjective than determining JNDs

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20
Q

3 classical psychophysical methods

A

method of constant stimuli, method of limits, method of adjustment

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21
Q

Discrimination

A

the ability to tell the difference between two stimuli or if a stimulus has changed

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22
Q

Suprathreshold stimulus

A

above the absolute threshold so always detectable

23
Q

Method of constant stimuli

A

standard and comparison stimuli presented together; magnitude of comparison (above and below standard) varies randomly from trial to trial

24
Q

Formula for JND

A

(upper limit - lower limit)/2

25
Q

Method of limits

A

standard and comparison stimuli are presented together, and you alternate between descending and ascending series while varying the starting point in each

26
Q

Method of adjustment

A

observer adjusts the comparison stimulus until it matches the standard stimulus while the experimenter randomly varies the starting point

27
Q

Advantages of method of constant stimuli

A

accurate and repeatable threshold values

28
Q

Disadvantages of method of constant stimuli

A

time-consuming; not good for children or clinical patients; not good for tracking thresholds over time; lots of data collected far from threshold

29
Q

Advantages of method of limits

A

saves time and not necessary to trace out the entire psychometric function

30
Q

Disadvantages of method of limits

A

habituation error (making the same response repeatedly) and anticipation error (changing response after a fixed number of trials)

31
Q

How to reduce habituation and anticipation errors in the method of limits?

A

alternate the series (requires extra series) and vary the starting point in each (requires extra stimulus levels)

32
Q

Advantages of method of adjustment

A

quick and participants like it

33
Q

Disadvantages of method of adjustment

A

not very accurate or repeatable

34
Q

2 modern improvements to the classic psychophysical methods

A

staircase method and 2-alternative forced-choice paradigm

35
Q

Staircase method

A

increase (or decrease) intensity of stimulus in equal steps until it can (or can’t) be detected

36
Q

Absolute threshold in the staircase method

A

the average of the cross-over points at response reversals

37
Q

Adaptive function of the staircase method

A

stimuli intensity keeps hovering around the absolute threshold by adapting the test sequence to the participant’s responses

38
Q

Advantages of using the staircase method

A

efficient, most data collected around the threshold (adaptive!), can be used to track threshold changes over time

39
Q

How do you reduce habituation and anticipation errors in the staircase method?

A

use randomly interleaved descending (strongest to weakest stimulus intensity) and ascending staircases

40
Q

What is the difference between a yes/no paradigm and the 2-alternative forced-choice paradigm?

A

former is subjective and the participant has to report whether they can detect or discriminate a stimulus; latter is more objective and the participant must prove that they can detect or discriminate the stimulus

e.g. Was the tone in the first or second interval? (detection) or in which interval are the 2 tones different? (discrimination)

41
Q

Advantages of using a 2-alternative forced-choice paradigm

A

accurate thresholds and reduces non-sensory differences among participants (bias or criterion differences)

42
Q

Cross-modality matching

A

scaling method in which the intensities of sensations that come from different sensory modalities are matched (e.g. brightness and loudness)

43
Q

How does the signal detection method provide a bias-free estimate of sensitivity?

A

the use of a 2-alternative forced-choice paradigm reduces perceiver bias/criterion because bias is measured directly

44
Q

2 factors affecting perceptual measurements in signal detection method

A

motivational state and sensory capacities of the perceiver

45
Q

Catch trials

A

trials in a signal detection experiment wherein the stimulus/signal is absent

46
Q

Sensitivity

A

the ease with which a perceiver can tell the difference between the presence and absence of a stimulus

47
Q

d’

A

the statistic that reflects a perceiver’s sensitivity

48
Q

What happens to the response outcome as you reduce stimulus intensity in a signal detection experiment?

A

reducing stimulus intensity decreases sensitivity (d’), so you make less hits and more false alarms

49
Q

2 reasons why people make false alarms

A

endogenous noise and criterion (β)

50
Q

Endogenous noise (sensory)

A

spontaneous neural activity that affects the measurement of thresholds and sensitivity

51
Q

Criterion (β)

A

response bias within a perceiver that depends on expectations and motivation

level above which sensation is attributed to the signal and not the noise

52
Q

How can you manipulate criterion in a signal detection experiment?

A

varying the stimulus probability or expectations

53
Q

What happens to the response outcome as you reduce stimulus probability

A

reducing stimulus probability increases criterion strictness or β (e.g. say “no” more so low hits and false alarms) but doesn’t affect sensitivity (d’)

PSYC 367 (7 decks)

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