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Stevens' power law Facts for Kids. Kiddle Encyclopedia.
Stevens' power law facts for kids
| Continuum | Exponent ( ) |
Stimulus condition |
|---|---|---|
| Loudness | 0.67 | Sound pressure of 3000 Hz tone |
| Vibration | 0.95 | Amplitude of 60 Hz on finger |
| Vibration | 0.6 | Amplitude of 250 Hz on finger |
| Brightness | 0.33 | 5° target in dark |
| Brightness | 0.5 | Point source |
| Brightness | 0.5 | Brief flash |
| Brightness | 1 | Point source briefly flashed |
| Lightness | 1.2 | Reflectance of gray papers |
| Visual length | 1 | Projected line |
| Visual area | 0.7 | Projected square |
| Redness (saturation) | 1.7 | Red-gray mixture |
| Taste | 1.3 | Sucrose |
| Taste | 1.4 | Salt |
| Taste | 0.8 | Saccharine |
| Smell | 0.6 | Heptane |
| Cold | 1 | Metal contact on arm |
| Warmth | 1.6 | Metal contact on arm |
| Warmth | 1.3 | Irradiation of skin, small area |
| Warmth | 0.7 | Irradiation of skin, large area |
| Discomfort, cold | 1.7 | Whole body irradiation |
| Discomfort, warm | 0.7 | Whole body irradiation |
| Thermal pain | 1 | Radiant heat on skin |
| Tactual roughness | 1.5 | Rubbing emery cloths |
| Tactual hardness | 0.8 | Squeezing rubber |
| Finger span | 1.3 | Thickness of blocks |
| Pressure on palm | 1.1 | Static force on skin |
| Muscle force | 1.7 | Static contractions |
| Heaviness | 1.45 | Lifted weights |
| Viscosity | 0.42 | Stirring silicone fluids |
| Electric shock | 3.5 | Current through fingers |
| Vocal effort | 1.1 | Vocal sound pressure |
| Angular acceleration | 1.4 | 5 s rotation |
| Duration | 1.1 | White noise stimuli |
Stevens' power law is a proposed relationship between the magnitude of a physical stimulus and the intensity or strength that people feel.
Most people think that it describes a wider range of sensations than Weber-Fechner law. But critics argue that the validity of the law is not sure.
The theory is named after psychophysicist Stanley Smith Stevens (1906–1973). Although the idea of a power law had been suggested by 19th century researchers, Stevens is credited with reviving the law and publishing a body of psychophysical data to support it in 1957.
The general form of the law is
where 
is the magnitude of the physical stimulus, 
is the psychophysical function capturing sensation (the subjective size of the stimulus), is an exponent that depends on the type of stimulation and 
is a proportionality constant that depends on the type of stimulation and the units used.
The table to the right lists the exponents reported by Stevens.it:Soglia percettiva