Science Fair Project Encyclopedia
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 = kIa
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:
| 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 | 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 irradiaton |
| 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 | Lifed 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-sec rotation |
| Duration | 1.1 | White noise stimuli |
See also
Last updated: 05-21-2005 18:45:19
12-19-2008 14:25:18
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details