quiz #1 Flashcards

Question

what is the method of adjustments?

Answer 1

observer adjusts the stimulus intensity, using a potentiometer until it is just detectable. The experimenter randomly adjusts the starting position of the potentiometer during each trial.

Answer 2

take the average of the threshold adjustments that the observer makes.

Answer 3

once we get into the range where we can always detect the stimulus, we can look at how much we have to change a stimulus in order to notice that it has been changed.

Answer 4

above the absolute threshold, always detectable.

Answer 5

the smallest difference between stimuli or change in a stimulus that the observer notices 50% of the time. This is also referred to as a just noticeable difference (JND).

Answer 6

method of constant stimuli, method of limits, and method of adjustments.

Answer 7

- presenting two stimuli at the same time, one is standard (fixed value) and the other is a comparison (value changes). - the magnitude of comparison (values are above and below threshold) is varied in random order with many trials of each value. - then plot % “stronger” responses versus comparison magnitude.

Answer 8

subtract the upper limit (0.75) from the lower limit (0.25) and divide by 2.

Answer 9

the point of subjective equality, which is a measure of accuracy. - 50% tells us how good we are at matching the weights.

Answer 10

the standard and comparison are presented together. - descending series: comparison decreases in equal steps until response changes from “stronger” to “equal” to “weaker.” - ascending series: comparison increases in equal steps until response changes from “weaker” to “equal” to “stronger.” - alternate between descending & ascending series; vary starting point

Answer 11

The upper limit is the crossover point between “stronger” & “equal” on each series The lower limit is the crossover point between “equal” & “weaker” on each series JND = (average upper limit -average lower limit) / 2 PSE = (average upper limit + average lower limit) / 2

Answer 12

observer adjusts the comparison stimulus until it matches the standard stimulus. - the experimenter will randomly vary the starting point.

Answer 13

``` JND = SD of the matches*0.6745 PSE = the averages of all the matches. ```

Answer 14

accurate and repeatable threshold values.

Answer 15

time-consuming, not good for tracking thresholds that change over time, not good for children or clinical patients, not efficient because too much unnecessary data is collected.

Answer 16

it requires too much time and attention that patients and children may not have.

Answer 17

efficient, no psychometric function necessary.

Answer 18

error of habituation, and error of habituation. | - to solve this we add more series and change the starting point, however, this decreases efficiency.

Answer 19

quick, participants like it.

Answer 20

not very accurate or repeatable threshold values.

Answer 21

the staircase method, and the 2-alternative forced-choice paradigm.

Answer 22

starts out similar to the method of limits. Stimulus intensity decreases (or increases) in equal steps until stimulus can’t be detected. Then, stimulus intensity increases (or decreases) until stimulus can be detected, etc. So essentially, we do not start a new series, we just change it from ascending to descending when the participant changes their response. adaptive method - stimuli kept hovering around threshold by adapting test sequence to participant’s responses. So the experimenter is adapting the stimulus based on the response from the participant.

Answer 23

response reversal.

Answer 24

after a fixed # of trials or a fixed # of reversals.

Answer 25

absolute threshold is the average of the cross-over points at response reversals.

Answer 26

efficient (most data is collected around the threshold). | can be used to track threshold changes over time.

Answer 27

Errors of anticipation and habituation. To avoid anticipation and habituation errors, randomly interleaved descending and ascending staircases can be used. This is difficult to do unless we have a computer.

Answer 28

The normal “yes/no” paradigm involves the participant reporting presence or absence of a stimulus (detection) or stimulus difference (discrimination). However, this is very subjective and the experimenter cannot verify or dispute the participants' response. This modern method is more objective since the participant must prove they can detect or discriminate the stimulus.

Answer 29

In this method, the 50% interval is the guess rate, and 75% becomes the absolute threshold. the psychometric function will start at the 50% mark. Percent correct is plotted rather than just yes responses.

Answer 30

Lower thresholds. People’s performances come out better because people are not allowed to guess. They are forced to choose an option. Reduces non-sensory differences between participants (bias or criterion differences).

Answer 31

Method of constant stimuli, method of limits, and the staircase method.

Answer 32

Ernst Weber discovered that difference thresholds are larger for larger stimuli. Weber’s Law: △I = k*I △I - the difference threshold k - is a constant that depends on the sensory system I - the physical magnitude of the stimulus Weber fraction (k) = △I/I Weber’s Law states that the difference threshold is a constant proportion of the physical magnitude of the stimulus. From Weber’s discrimination experiments, he determined that the JND is larger for larger standard stimuli (I), with a linear relationship.

Answer 33

Fechner wanted to quantify sensation. He suggested using JNDs to describe the perceived intensity. For example, A is 3 JNDs above your absolute threshold for detection; B is 2 JNDs brighter than A. Fechner then used Weber’s findings to describe the sensation. If we assume that JNDs produce equal steps in sensation (△S), then sensory steps at the upper end of scale require larger increases in stimulus intensity (logarithmic relationship).

Answer 34

Fechner’s Law: a principle describing the relationship between stimulus magnitude and resulting sensation magnitude (scaling). S = k log R k - Weber fraction R - stimulus level (same as I in Weber’s law) Essentially, as stimulus intensity increases, sensation intensity increases rapidly at first, but then more slowly. Sensation magnitude has a logarithmic relationship since sensory steps at the upper end of the scale require larger increases in stimulus relationships.

Answer 35

Fechner Laws - describes stimulus magnitude, and the resulting sensation magnitude. Weber was trying to see what had to be done for an individual to notice a difference whereas Fechner wanted to know what people were experiencing with these changes (as in brightness, loudness, etc.).

Answer 36

participant assigns a number to describe stimulus intensity. This is a very simple way to do psychophysical scaling. Magnitude estimation experiments showed that once detected, the sensory magnitude of a stimulus increases with its physical magnitude, within limits. The rate of increase varies with different sensations.

Answer 37

a principle describing the relationship between stimulus magnitude and resulting sensation magnitude, such that the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent (or power). S = a*I^b S = sensation I = stimulus intensity a = constant that corrects for units. b = exponent (will determine the shape of the curve). Stevens Law and Fechner’s law predict the same scaling result for sensory modalities in which b < 1, but not for other sensory modalities.

Answer 38

Fechner’s law assumes that all JNDs are perceptually equal, but this law is violated for some sensory modalities. magnitude estimation is more subjective than determining JNDs.

Answer 39

a scaling method in which the intensities of sensations that come from different sensory modalities are matched. This is used to sensory differences across individuals. This method has shown us that the relationship between visual experience and auditory experience appears to be similar across individuals. However, being able to match intensities of sensations from different sensory experiences does not hold for all sensory experiences. for example: taste.

Answer 40

Recognizes that perceptual measurements are influenced by the motivational state and sensory capacities of the perceiver. It also understands that all decisions are made in the presence of noise.

Answer 41

trials in a signal detection experiment on which the stimulus/signal is absent.

Answer 42

the ease with which a perceiver can tell the difference between the presence and absence of a stimulus. - If a participant has perfect sensitivity they would have a hit rate of 1.0. - However, if the participant is completely insensitive, they will have equal hit and false alarm rates.

Answer 43

hits and false alarm.

Answer 44

the statistic that reflects a perceiver’s sensitivity. If the two distributions have less overlap, d’ is larger. reducing stimulus intensity decreases sensitivity (d’). Refer to the dot example from class.

Answer 45

sensory and non-sensory distractions. sensory: reducing stimulus intensity decreases sensitivity (d’). Refer to the dot example from class. non-sensory: criterion.

Answer 46

response bias within a perceiver; depends on expectations & motivation.

Answer 47

response pattern.

Answer 48

High stimulus probability → high hits and false alarms. SMALL β VALUE. Low stimulus probability → low hits and false alarms. LARGE β VALUE. Here we change the response pattern by varying the stimulus probability, but NOT the sensitivity. d’ stays the same, but β CHANGES. Higher β = stricter criterion.

Answer 49

Sensitivity (d’) depends on the overlap of signal absent and signal present distributions. If you are completely insensitive d’ is zero. If there is more distance, sensitivity is higher because the two distributions are distinctly different. d’ = distance between the means of N and S+N distributions.

Answer 50

A liberal/lax criterion (small β) produces high hits and high false alarms. A conservative/strict (large β) produces low hits and low false alarms.

Answer 51

If you plot false alarms on the x-axis of a graph against hits on the y-axis for different criterion values, you get a curve known as a receiver operating characteristic (ROC) curve.