Lecture 3&4 - Study Guide

Question 1

the psychophysical methods

Answer 1

qualitative vs. quantitative methods

Question 2

qualitative methods

when to use?

Answer 2

• Description (phenomenological method)
– Provide a general physical description of the
stimulus.

• Recognition
– Name the stimulus or identify what category it belongs to.

These are more useful in clinical settings to assess
behavioral or sensory dysfunction.

− These are primarily useful in clinical contexts.

Question 3

quantitative methods

Answer 3

Detection
– Absolute threshold: Smallest amount of stimulus energy required for detection.

– Difference threshold: Smallest difference between two stimuli that can be detected.

• Magnitude estimation

• Visual search and reaction time
- These help characterize the regularities between physical stimuli and psychological states.

Question 4

the meaning of Weber’s law.

Answer 4

Early on, it was noticed that the
value of DL (JND) increases with the
magnitude of the standard stimulus.

DL / S = K

K is a constant, S is the value of the
standard, and DL is the difference
threshold

Question 5

magnitude estimation

Answer 5

how we quantify the perceived difference between two stimuli of different intensities

• Present two stimuli (one is usually a standard with an arbitrary value), and ask the observer to assign a value to the comparison stimulus.

• Repeat the process with many comparison intensities.
• Plot the values for all the observations.

Question 6

response expansion

Answer 6

If perceived magnitude increases faster

than stimulus intensity,

Question 7

response compression

Answer 7

describes magnitude increasing more slowly than stimulus intensity

Question 8

Steven’s Power law

Answer 8

describes the relationship between perceived magnitude and stimulus intensity for a given sense.

P = KS^n

P is the perceived magnitude.

K is a constant

S is the stimulus intensity, raised to the power n.

If n > 1, then response expansion; n < 1, then response
compression

Question 9

how reaction time is used as a measure in visual search paradigms.

Answer 9

In a visual search paradigm, we are interested in the time it takes to detect a target stimulus.

The reaction time, the time between presentation of the stimulus and the response, can help define the mechanisms involved in perception (i.e. may indicate different algorithms being used).

In studies of tumor detection and identification, visual search is combined with qualitative assessments, eye-tracking, and threshold
estimates to measure performance. (experts take less time to locate tumors in pictures)