Chapter 1 - Principles of Perceptual Measurement

Question 1

Absolute threshold

Answer 1

minimum physical intensity that is required for a stimulus to be detected. Aka.. detection threshold

Question 2

correct rejection

Answer 2

when no stimulus is present in a trial (noise trial) and the subject answers NO

Question 3

criterion (beta)

Answer 3

a set-point or cut-off point that is internally established by the subject. On those trials where sensory magnitude exceeds B, the subject will indicate that a detectable sensory event has occurred and will respond YES. If the sensory magnitude fails to reach B, then the subject will respond NO.

Question 4

cross-modality matching

Answer 4

the use of stimuli from different domains (e.g., sound vs. light intensity) to make comparisons of the relative magnitudes that are produced in different sensory systems

Question 5

d’ (d prime)

Answer 5

difference between the means of the noise and signal + noise distributions. According to SDT, d’ can increase either by increasing the strength of the signal or by increasing the sensitivity of the detector

Question 6

difference threshold

Answer 6

minimum change in physical intensity that is required for a noticeable change in sensation. Difference thresholds are always determined at suprathreshold levels. Aka. discrimination thresholds

Question 7

discrimination scaling

Answer 7

application of difference threshold measurements to estimate sensory magnitude functions. The theoretical foundation for this approach is based on the notions that JNDs represent a constant unit of sensory change, regardless of the actual operating level. Aka. confusion scaling

Question 8

Ekman’s Law

Answer 8

The amount of sensory change needed to produce a JND is not a constant, as Fechner postulated, but rather a linear function of the initial or operating level of sensation. Ekman’s Law is the sensory counterpart of Weber’s law

Question 9

false alarm

Answer 9

when no stimulus is present in a trial (noise trial) and the subject answers YES

Question 10

Fechner’s law

Answer 10

logarithmic function relationship between stimulus intensity and sensation magnitude

Question 11

function

Answer 11

mathematical description of how one variable is related to another and generally expressed as a formula

Question 12

hit

Answer 12

when a stimulus is present in a trial (signal + noise trial) and the subject answers YES

Question 13

ideal detector

Answer 13

a detector (animal or machine) that can always detect a signal when its intensity is above a certain defined level (threshold) and always fails to detect it when it is below that level

Question 14

intramodal matching

Answer 14

comparing different aspects of a stimulus within a particular sensory domain or modality(e.f., different wavelengths of light on brightness perception, different tone frequencies on loudness perception, taste sensations generated by sweet vs. sour substances, etc.)

Question 15

just noticeable difference (JND)

Answer 15

a change in sensation (delta S) that is sufficient to allow that mental event to be just detected. the JND, which is a psychological parameter and therefore cannot be experimentally determined, is the subjective counterpart of the difference threshold (delta I), which is a physical parameter that can be experimentally derived.

Question 16

magnitude estimation

Answer 16

psychophysical scaling procedure developed by Stevens in which human subjects are required to make numerical estimates of the sensory magnitudes that are evoked by stimuli of different physical intensities

Question 17

metathetic

Answer 17

sensations that rely on a substitutive process such that changing some aspect of the stimulus alters the quality of the sensory impression

Question 18

Method of Adjustment

Answer 18

psychophysical method in which the subject directly adjusts stimulus intensity to produce a detectable sensation. the threshold is calculated from the means of several trials

Question 19

Method of Constant Stimuli

Answer 19

psychophysical method in which stimulus intensity values are randomly chosen from a preset range. The subject’s responses over many trials are stored and later used to generate a response frequency for each intensity level

Question 20

Method of Limits

Answer 20

psychophysical method in which stimulus intensity is systematically increased or decreased by the experimenter until the subject gives a change in response

Question 21

miss

Answer 21

when a stimulus is present in a trial (signal + noise trial) and the subject answers NO

Question 22

multi-dimensional scaling

Answer 22

representation on a spatial map based on the similarity or dissimilarity of the sensory impression produced by metathetic stimuli

Question 23

noise

Answer 23

Background activity that is unrelated to the stimulus and which can interfere with its detection

Question 24

ogive

Answer 24

S-shaped response function that is typically seen in psychophysical experiments where detection of discrimination performance is measured

Question 25

Power law

Answer 25

relationship deduced by Stevens in which sensory magnitudes are related to stimulus intensity raised to some power (exponent)

Question 26

prothetic

Answer 26

sensations that rely on an additive process where changing some aspect of the stimulus alters the magnitude of the sensory impression

Question 27

psychometric function

Answer 27

relationship between performance on a psychophysical task (e.g., proportion of times a stimulus is detected) and some feature of the stimulus (e.g., intensity)

Question 28

psychophysics

Answer 28

the study of quantitative relationships between physical evens and psycholofical experiences

Question 29

ratio scaling

Answer 29

direct estimations of sensory magnitudes produced by stimuli of different intensities. the technique is based on the theory that sensory magnitudes fall on a ratio scale and can therefore be directly measured by the perceiver.

Question 30

receiver operating characteristic (ROC)

Answer 30

graphical plot of hits versus false alarms that shows how these values change with respect to each other at all possible criterion levels

Question 31

response bias

Answer 31

influence of factors unrelated to the sensory stimulus in the decision-making process that elads to judgments about that stimulus

Question 32

scaling

Answer 32

general psychophysical procedure to estimate the amount or magnitude of something related to perception or some other aspect of psychology

Question 33

sensory transducer theory (SDT)

Answer 33

notion that transformation (transduction) of physical energy in the stimulus into biological (neural) signals is the basis of the power law. According to this theory, the power law exponent depends on the sensory mechanisms that are involved int his process

Question 34

staircase procedure

Answer 34

this is an example of an adaptive procedure in which the sequence of stimulus presentations is varied according to the subject’s response

Question 35

step function

Answer 35

response function that makes an abrupt transition from one level to another

Question 36

stimulus

Answer 36

object or event in the physical world that may be perceived through stimulation of one of the sensory systems

Question 37

subthreshold

Answer 37

physical intensity values that are below absolute threshold and therefore not detectable

Question 38

suprathreshold

Answer 38

physical intensity values that are above absolute threshold and therefore generally detectable

Question 39

two-alternative forced choice (2AFC)

Answer 39

experimental procedure where two presentations are made with only one of them containing the stimulus. the subject’s task is to identify the presentation with the stimulus. Criterion effects are minimized int his procedure

Question 40

Weber’s fraction (k)

Answer 40

proportion by which the difference threshold (delta I) increases with intensity to produce a just noticeable difference in sensation. The Weber fraction is given by the formula: k = delta I / I

Question 41

Weber’s law

Answer 41

difference threshold (delta I) increases in a linear fashion with the intensity (I) at which the sensory discrimination is being made. The proportionate increase is given by the constant k in Weber’s law