Principles of Perceptual Measurement

Question 1

What 5 characteristics of a stimulus do we need in order to describe it?

Answer 1

Intensity
Location
Time
Duration
Content

Question 2

What are three types of psychophysical methods for determining stimulus intensity?

Answer 2

Method of Adjustment (play with this dial till you see something)
Method of limits (I’m going to play with this dial for you, tell me when you see something)
Method of constant stimuli (do you see this? this? THIS?)

Question 3

How many trials per stimulus level are needed to form an accurate measure?

Answer 3

Over 20

Question 4

What is Weber’s Law?

Answer 4

Difference threshold = Weber’s constant x Intensity

For a constant change in eg brightness (eg 25%), you will require more and more stimulus (a candle will need to increase its intensity less than a floodlight would)

Question 5

What is Fechner’s Law?

Answer 5

Sensation = Constant x Log of Intensity

Sensation is a constant amount, but the intensity must increase more and more for each JND