stevens' power law

Stevens' power law relates the intensity of a stimulus to its perceived strength. It supersedes the Weber-Fechner Law, since it can describe a wider range of sensations. The theory is named after its inventor, S. Smith Stevens (1906–1973). The formula is:

S = k I ^a

where S is the amount of sensation, k is a constant, I is the stimulus intensity, and a is an exponent. a is dependent on the type of stimulation. Stevens measured the following exponents:

Exponent	Stimulus condition
oudness	0.67	Sound pressure of 3000-Hz tone
ibration	0.95	Amplitude of 60 Hz on finger
ibration	0.6	Amplitude of 250 Hz on finger
rightness	0.33	5 target in dark
rightness	0.5	Point source
rightness	5	Brief flash
rightness	1	Point source briefly flashed
ightness	1.2	Reflectance of gray papers
isual length	1	Projected line
isual area	0.7	Projected square
edness (saturation)	1.7	Red-gray mixture
aste	1.3	Sucrose
aste	1.4	Salt
aste	0.8	Saccharine
mell	0.6	Heptane
old	1	Metal contact on arm
armth	1.6	Metal contact on arm
armth	1.3	Irradiation of skin, small area
armth	0.7	Irradiation of skin, large area
iscomfort, cold	1.7	Whole body irradiation
iscomfort, warm	0.7	Whole body irradiaton
hermal pain	1	Radiant heat on skin
actual roughness	1.5	Rubbing emery cloths
actual hardness	0.8	Squeezing rubber
inger span	1.3	Thickness of blocks
ressure on palm	1.1	Static force on skin
uscle force	1.7	Static contractions
eaviness	1.45	Lifed weights
iscosity	0.42	Stirring silicone fluids
lectric shock	3.5	Current through fingers
ocal effort	1.1	Vocal sound pressure
ngular acceleration	1.4	5-sec rotation
uration	1.1	White noise stimuli

Stevens' Power Law

See also