Pyschophyical methodology

Question 1

Definition of threshold

Answer 1

The point at which a physiological effect begins to be produced

Question 2

What is detection

Answer 2

Is something there

Question 3

What is discrimination

Answer 3

Change in supra-threshold stimulus

Question 4

What factors affect threshold

Answer 4

Intrinsic noise
Observer criterion
Extrinsic noise

Question 5

Intrinsic noise

Answer 5

Spontaneous neural activity

Question 6

Observer criterion

Answer 6

How much physical change is required before the subject is comfortable accepting an event occured

Question 7

Extrinsic noise

Answer 7

Fluctuation of the number of photons of light that reach the retina from the stimulus

Question 8

What can only be minimized during threshold testing?

Answer 8

Objective criterion

Question 9

What are the pyschophysical methods of measuring a threshold

Answer 9

Limits
Adjustment 
Staircase 
Constant stimulus 
Forced-choice

Question 10

Ascending limits

Answer 10

Stimulus intensity is gradually increased in each successive presentation until the patient reports detection

Question 11

Descending limts

Answer 11

Stimulus intensity is gradually decreased in each successive presentation until the patient reports they can barely see it

Question 12

Method of adjustment

Answer 12

Subject has complete control of the rate and magnitude of stimulus itnensity change

Question 13

Ascending staircase

Answer 13

Sub-threshold presented until detection, then decrease light until reversal, repeat

Question 14

Descending stiarcase

Answer 14

Supra-threshold presented, decreased until reversal of response, repeat

Question 15

Constant stimulus

Answer 15

Fixed range of stimulus values used and presented repeatedly in random order
Subject must determine detection or if one is greater than a standard

Question 16

What is threshold in the constant stimulus detection?

Answer 16

Stimulus value that coincides with 50% correct

Question 17

What is threshold in constant stimulus discrmination?

Answer 17

Stimulus interval between 84% adn 50% correct

Question 18

Point of subjective equality

Answer 18

50% point for discrimination when subject does not perceive change in stimulus value

Question 19

What makes forced-choise different?

Answer 19

Subject is forced to make a positive response regardless of whether the stimulus is seen

Question 20

What is the preferred pyschophysical method?

Answer 20

Forced-choice

Question 21

Where does the 2 alternative psychometric function begin?

Answer 21

50%

Question 22

Where is the threshold in a 2 alternative forcced choice?

Answer 22

at the 75% correct stimulus intensity

Question 23

Where does the 4 alternative psychometric function begin?

Answer 23

25%

Question 24

Where is the threshold in a 4 alternative forced choice?

Answer 24

62.5% correct stimulus intensity

Question 25

How do you calculate the guess rate?

Answer 25

1/number of choices

Question 26

What does the signal detection theory do?

Answer 26

Estimate the effects of observer sensitivity and observer bias

Question 27

What is the discriminability index?

Answer 27

Measure of the separation between noise and signal plus noise distributions

Question 28

How do you calculate the discriminability index?

Answer 28

Separation divided by spread

Question 29

What is separation?

Answer 29

difference between the means of the noise and S+N distributions

Question 30

What is spread?

Answer 30

standard deviation of the distributions

Question 31

What does a higher discriminability index mean?

Answer 31

Less of an overlap and an easier to detect stimulus

Question 32

Strict criterion

Answer 32

Large change in internal response must occur for a subject to report that they detect the stimulus

Question 33

Laxed criterion

Answer 33

Subject is willing to accept that the smallest change in internal response that they detect as being different must mean that a stimulus was present

Question 34

Who has a higher threshold?

Answer 34

Strict

Question 35

Who’s criterion line will intersect a larger proportion of the noise only distribution?

Answer 35

Laxed

Question 36

Who attempts to maximize the times they are correct?

Answer 36

Laxed

Question 37

Who attempts to minimize the times they are incorrect?

Answer 37

Strict

Question 38

False positive

Answer 38

Responding yes when there isnt a stimulus

Question 39

Hits

Answer 39

Responding yes when there is a stimulus

Question 40

False negatives

Answer 40

responding no when there is a stimulus

Question 41

Rejections

Answer 41

Responding no when there is not stimulus

Question 42

Pay-off matrix

Answer 42

Attempt to influencee subject’s criterion to force subject to tend toward strict or laxed

Question 43

Weber’s law

Answer 43

Threshld to detect a stimulus will vary proportionally with the magnitude of the stimulus itself

Question 44

Fechner’s law

Answer 44

Proposed that a stimulus magnitude produces the same unit change in the internal perceptual response

Question 45

Steven’s power law

Answer 45

Magnitude of the perceptual experience varies with a power law of the physcial stimulus magnitude

Question 46

Magnitude estimation

Answer 46

Subject trained to use a scale to quantify the magnitude of their perceptual experience