What do Weber fractions tell you about sensation?
Can we perceive subliminal messages?
How does the visual system work?
How do we perceive the world around us?
Psychophysics and psychophysiology
relation between physical stimulus and psychological response
Fechner: “Father of Psychophysics”
Can determine a just noticeable difference
Value of a stimulus characteristics require to produce some response
Absolute: Lower limit
Difference: Amount of change for JND
Vision: Candle flame at 50km
Hearing: Tick of a watch at 6m.
Taste: Tsp. of sugar in 8L of water
Smell: 1 drop of perfume in a 6 room apt.
Touch: Wing of a fly falling on cheek from 1cm
So what’s the relation
E.g. Brightness and perceived brightness
Not a 1 to 1 relation
Size of difference threshold relative to physical intesity of test is constant
Must know how to calculate on Exam
∆I / I = C
If I = 50db and a JND is reported at 55 db 1 / 10 = 5 / 50 = C
1. Can predict other JND’s
E.g. Whats a JND @ 100 db
∆I = 10
A JND would occur @
new test + 10 = 110 db OR
new test - 10 = 90 db
Value of JND not constant
The relative difference is...
1. Can compare sensitivity of different systems
Vision (Brightness) = 1/60
Kinesthesis (Weights) = 1/50
Pain (Thermal) = 1/30
Audition (Mid. Pitch; Mod. Lou